Waste management using marine microorganisms

ABSTRACT

Waste management is one of the most pressing environmental issues due to the result of human activities with changes in lifestyle and consumption patterns. To combat this, waste minimization solutions have been built on the basis of the waste hierarchy so as to procure practical value from the product source. However, efforts taken in the previous stages have turned out to be uneconomical and resulted in immense quantities of chemical waste. The challenges and barriers are significant, but so are the opportunities. Therefore, the usage of marine organisms has been recommended as an efficient alternative in the waste management process because of its unique attributes. The bacterial communities among marine habitats play an important part in the global biogeochemical cycle due to their diverse metabolic capacities. Marine microorganisms have unique biodegradation processes for dissolving a broad range of organic contaminants, either as individual strains or as members of microbial consortia. They have the ability to degrade, alter, or create a wide range of compounds created naturally or by man-made processes. These microorganisms are actively involved in nutrient cycling and productivity and, therefore, aid in balancing the ecosystem by managing the concentrations of pollutants. Intense research on marine microorganisms through all these years has gathered that marine microorganisms play a crucial role in the production of non-toxic biosurfactants and biopolymers. Furthermore, a deeper comprehension of the harmful heavy metals that interact with marine microbes has led to the suggestion that these microbes could be used in a variety of ways to treat contaminated water systems. The core of this paper reports the literature on the degradation of organic wastes, inorganic wastes and wastewater by several marine microorganisms that can break down and extract toxic substances from the environment. This review paper attempts to explore the potential of marine microorganisms in depth. Marine microorganisms have demonstrated their significance through a novel source of their enzymes, paving a promising scope for the industry and academia. A significant fraction of these organisms have not been identified, and their enzyme activity has not been studied due to exploratory limitations. Therefore, profiling the role of marine microorganisms in waste management will enable us to observe the significant benefits in the long run. Also, this paper has emphasized the challenges and opportunities involved in the usage of marine microorganisms and the outputs acquired in this bioeconomy era. Utilizing these resources has exposed several natural products that may present several opportunities for biotechnological applications. This will also provide us with the treatment outcome to overcome their adverse properties, if any, and deliver effective ways to advance the use of marine microorganisms in waste management systems.

KEYWORDS:

• marine microorganisms
• organic contaminants
• nutrient cycling
• biosurfactants

1. Introduction

Waste materials are considered to be undesirable by-products or residues generated as a result of any negative values from the production site (Peng et al., 2018). Recently emerged large-scale businesses have indulged in the exhaustive usage of chemical pollutants and radioactive materials, resulting in environmental repercussions associated with overall management (Reis Neto, 2021). Also, urban sustainability has faced challenges from the ever-worsening environmental issues brought about by the rapid expansion of industrialization and urbanization. This calls for a clever method to monitor the dynamics of these issues across many regions and nations. As one of the essential components of sustainable development, environmental sustainability has drawn more attention recently in an effort to meet the Sustainable Development Goals set forth by the United Nations. These developing countries had designed a framework within the scope of waste management; a comprehensive approach that can be used in the processing, development, implementation, monitoring, and improvement of a strategy at both the local and central levels (Okedu et al., 2022).

In light of the aforementioned strategies, problems had been increasing on par with the developmental approaches. As aquatic ecosystems and terrestrial environments are intertwined, changes in one system have an impact on the other. Also, coastal and marine ecosystems have become stressed for decades due to a variety of factors, exclusively anthropogenic activity, where pollution and environmental mismanagement have been considered to be the root cause of these aspects. Also, due to unsustainable development and building operations, marine and coastal systems have been exposed to serious risks. With rapidly increasing population and urbanisation rates, waste production has soared, imposing a significant challenge for global sustainable development. Wastewater and sewage wastes have triggered all these environmental aspects, and their composition is discussed in Figure 1 (Okedu et al., 2022).

Figure 1. Typical composition of waste water and sewage waste.

These issues have resulted in undesirable changes to the ecosystem causing aesthetic damage with the reduction in the economic value of natural sources. Trash prevention/minimization, waste re-use, recycling, and composting have been prioritized in a waste management hierarchy derived from the most environmentally sound criteria. To rule out the detrimental effects, waste products have been disposed of through diverse techniques, as mentioned in Figure 2 (Heidari et al., 2019).

Figure 2. Hierarchy of waste management process.

Here, microorganisms have a promising role to play in this situation. The distinctive characteristics of microorganisms can be efficiently utilized to revive the environment (Katinas et al., 2019). They imply the mechanism of aerobic and anaerobic digestion where the former involves the digestion of organic waste by altering the chemical make-up of the material ultimately converting them into the least damageable environmental matter. While the latter involves the biological fermentation of organic matter, making them more environmental friendly. Here, anaerobic microorganisms break down microplastic into microbial biomass, carbon dioxide, methane, and water when methanogenic conditions are satisfied, while aerobic microorganisms break down microplastic into microbial biomass, carbon dioxide, and water depending on the environmental conditions (Buragohain et al., 2020). Especially, these microorganisms have great potential and efficacy in degrading various toxic compounds (Mishra et al., 2021).

Among all, marine microorganisms are considered to be superior in enzyme production to that of plants or animals. The biological and chemical diversity found in the maritime environment is extensive. More than 70% of the Earth’s surface is made up of it, which has a wide variety of habitats and frequently exhibits extreme weather conditions. In spite of unfavorable situations, marine creatures thrive there, providing a huge reservoir for microbes and enzymes. Due to the differences between marine and terrestrial ecosystems, it is possible to identify and isolate enzymes and microbes that are novel or have distinguishing characteristics from their terrestrial counterparts (Izadpanah et al., 2018).

Interestingly, the special cold-adapted enzymes found in marine microbes offer a wealth of options for biotechnological applications and shed light on a variety of practical problems, including plastic pollution. The current efforts to reduce energy demand have sparked interest in several industrial uses for the enzymes found in psychrophilic bacteria. Due to the decrease in the amount of electric energy used for heating, this might be a major benefit in the deterioration process (Viel et al., 2023).

Despite their potency, there are many untapped sources of marine-derived enzymes, and their investigation is limited. Till now, only a fraction of marine microorganisms on earth has been exploited for screening of their potent values. Novel techniques used for the cultivation and production of marine microorganisms, as well as cloning and overexpression of their genes in various expression systems, will pave the way to use these marine enzymes or marine microorganisms for chemical, food, pharmaceutical, and other industrial applications (Sivaperumal et al., 2018). Therefore, this review paper has focused on the novel aspects of marine microorganisms their possible applications and implement their use in real- world environmental applications.

2. Application of marine microorganisms towards waste management progress

Marine microorganisms are diverse and have a one-of-a-kind ability to manufacture natural products, and their significance for marine biotechnology has just lately been recognized by the scientific community. They possess distinct characteristics as they thrive under extreme conditions such as high temperatures (−15°C to 110°C), salt, extreme pressure, and play a significant role in oceanic processes such as breakdown of complex products into simple forms, recycling of nutrients, and biodegradation. These microbial activities aid in the maintenance of an equilibrium condition in the marine environment, which is critical for the survival of other organisms. Also, the metabolic routes and physiological modifications made by marine bacteria demonstrate their adaptability to change under biological, chemical, and physical circumstances (Sivaperumal et al., 2018; Urbanek et al., 2018). Therefore, they have been explored for a variety of biotechnological uses, ranging from pharmacological bioactive substances to other high-value goods like enzymes, pigments, nutraceuticals, and cosmetics (Andrady & Neal, 2009).

3. Degradation of organic wastes

Research through all these years have stated that marine bacteria uplifts the production of PHA (Polyhydroxyalkonoates) generation process, and have garnered increased interest recently. The blue bioeconomy, which is centered on the maritime and marine industries, promotes the sustainable use and exploitation of marine resources. In particular, marine bacteria are recognized to have a high degree of biodiversity and considerable biotechnological potential that can be exploited to produce the building blocks for bioproducts and biomaterials (Mitra et al., 2020; Yakimov et al., 2022).

Since chemically produced biodegradable plastics do not acquire a specific pathway for degradation, they are broken down using co-metabolism mechanism. Contrarily, specialized P(3HB) depolymerases have been used to breakdown biologically produced polymers like PHA. In this situation, specific marine P(3HB) depolymerases have been modified to catalyze PHA depolymerization at pH, temperature, and salinity levels that are comparable to those of seawater. Numerous hydrocarbon-degrading bacteria, including Pseudomonas, Alcanivorax, and Marinobacter spp., have been identified among marine PHA-degrading bacteria (Imhoff et al., 2011). For example, Zadjelovic et al. showed that a number of species in the Alcanivorax genus carry genes that encode PHA depolymerase ALC24_4107. An enzyme of this kind can hydrolyze aliphatic polyesters, including P(3HB), P(3HB-co-3HV), PES, PBS, and PCL, which can be of natural or manufactured origin. Additionally, the extracellular P(3HB) depolymerase produced by the P. stutzeri YM1006 and Marinobacter sp. NK-1 strains is active against both P(3HB) and (R)-3HB (Suzuki et al., 2021).

Regarding one of the most extensively researched oil-degrading marine bacteria, Alcanivorax borkumensis, scientists found that a significant increase in PHA formation was observed in a mutant strain of A. borkumensis when hydroxyacyl-CoA-specific thioesterase, which acts only on hydroxylated acyl-CoAs, was blocked. This is because cellular intermediates of alkane breakdown, namely CoA-activated hydroxylated fatty acids, are being redirected towards PHA. Growing on alkane, a tesB-like mutant produced 20 times more PHA than a wild-type strain cultivated in the same circumstances. PHAs in this mutant bacteria are expelled and accumulate extracellularly, which enhances their biotechnological usefulness, in contrast to other bacteria (Dubey & Mishra, 2021).

It has also been reported that the genus Novosphingobium has been found to be an efficient poly aromatic hydrocarbon degrader. The physiological and genome-wide transcription analyses of LH128-GFP cells implanted into PAH-contaminated soil clearly indicated that most LH128-GFP cells quickly enter a viable but non-culturable-like state. This process indicates that those viable but non-culturable-like LH128-GFP cells are metabolically active and appear to respond quickly to environmental inputs in the soil by expressing stress-resistance pathways (Fida et al., 2017)

Recently, the search for degrading microbes in deep marine sediments where temperatures drop below 4°C has recently become the main focus of research. In Toyama Bay, two different kinds of PCL (polycaprolactone)-degrading bacteria were found in the 320 m depth of the ocean. The isolated bacteria could break down PCL at 4°C and were recognised as belonging to the Pseudomonas genus. Additionally, isolated bacteria from Shewanella sp., Moritella sp., Psychrobacter sp., and Pseudomonas sp. found in deep-sea sediment samples collected at a depth of 5000–7000 m were able to degrade a biodegradable polyester called PCL Recently, Halomonas boliviensis has been reported to be involved in the degradation of bilge water (Crisafi et al., 2022a).

Also, Serratia marcescens ABHI1001 has effectively involved in biodegradation of organic pollutant, p-cresol. This marine bacterium has achieved 85% of degrading efficiency within 18 hours and so can be upgraded for further industrial applications (T. Singh et al., 2017). Recent research has reported a strain, Acetobacter orientalis XJC-C, a newly found cellulolytic bacterium with salt and high-temperature resistance, isolated from a marine soft coral. This strain, can biodegrade a variety of lignocellulosic agricultural wastes, including banana straw. At 40^th day of the experiment, highest levels of cellulolytic and ligninolytic enzyme activity were identified. Also, the lignin degradation rate in the A. orientalis XJC-C group increased by 47.08% when compared to the negative and positive control groups. As a result, A. orientalis XJC-C has become a potential choice for lignocellulosic agricultural residue degradation (Crisafi et al., 2022b). Their mode of action is represented in Figure 3

Figure 3. Degradation of organic wastes by marine bacteria.

4. Degradation of inorganic wastes

In the realm of bioremediation, marine microorganisms have demonstrated great advantage over other types of microbes as they possess diverse metabolic mechanisms for the breakdown and eradication of specific environmental pollutants. Several reports have been made on the removal of harmful heavy metals utilising different marine microorganisms. Also, they are efficiently involved in phosphorus removal, nitrogen fixation and oil treatment that are used for ecological restoration in order to quickly and efficiently recover the existing offshore water pollution (Peng et al., 2018).

Also, the metabolic routes and physiological modifications made by marine bacteria demonstrate their adaptability to change under biological, chemical, and physical circumstances. Similarly, microorganisms that are exposed to metals develop resistance mechanisms. Metal resistant genes are frequently found in plasmids harboring antibiotic resistance genes. Recently, researchers discovered Pseudomonas aeruginosa strains from sewage-contaminated areas along the Spanish coast that withstand simultaneous exposure to few antibiotics and heavy metals. Also, a single strain isolated from highly polluted sea water has been found to be resistant to Hg, As, and Cr (Dang & Lovell, 2015)

This shows that a single bacterium can have several resistances to metals and antibiotics. Metal resistance can also emerge when the choice of detoxification route is influenced by the presence of detoxification genes. Metal sequestering proteins called metallothioneins (MT) present in the marine cyanobacterium Synechococcus sp. has been reported to be resistant to cadmium (Edet et al., 2023).

With regard to the degradation of plastics using marine microorganisms, Ideonella sakaiensis 201-F6, had been recently identified and proven to be capable of degrading polyethylene terephthalate (PET) by using it as an energy and carbon source. Similarly, Anoxybacillus rupiensis Ir3 (JQ912241), a thermophilic bacterium isolated from hydrocarbon-polluted soil in Iraq, had expressed a good potential for using aromatic compounds as carbon sources and degradation of plastic products (Atanasova et al., 2021). Although there has been evidence of polyethylene terephthalate (PET) biodegradation by microorganisms, little is known about the molecular mechanism and process of PET biodegradation by marine microbes. Through activity tracking, researchers were able to identify the enzyme known as PET esterase, which breaks down PET. Apart from depolymerizing PET, it also hydrolyzes mono-(2-hydroxyethyl) terephthalate (MHET) in an acidic environment to produce terephthalic acid (TPA). They demonstrated that it is a membrane-anchored, low transcription-level protein that is expressed on the surface of cells. With the acquired information recent research has revealed that these five bacterials isolates, namely, Alcanivorax xenomutans BC02_1_A5, Marinobacter sediminum BC31_3_A1, Marinobacter gudaonensis BC06_2_A6, Thalassospira xiamenensis BC02_2_A1, Nocardioides marinus BC14_2_R3 and Rhodococcus pyridinivorans P23 play a crucial role in depolymerization of PET and could effectively remove the PET pollutants [25 (Gao & Sun, 2021; Guo et al., 2023). The action of several marine microorganisms over plastics is discussed in Table 1.

Table 1. Action of marine microorganisms over plastic degradation

Plasticizers	Marine bacterial isolates
Dibutyl phthalate (DBP)	Mycobacterium sp. DBP42 and Halomonas sp. ATBC28
Bis(2-ethyl hexyl) phthalate (DEHP)	Mycobacterium sp. DBP42 and Halomonas sp. ATBC28
Polyethylene terephthalate (PET)	Thioclava sp. BHET1, Bacillus sp. BHET2, Oceanospirillales, Rhodobacteraceae, Saprospiraceae, Betaproteobacteria, Myxococcota and Gammaproteobacteria
Isopthalate	Syntrophorhabdus aromaticivorans
PE	Alcanivorax borkumensis, Oceanospirillales, Vibrionaceae, Rhodobacteraceae, Saprospiraceae
PS	Oceanospirillales, Vibrionaceae, Rhodococcus ruber
Dibutyl phthalate	Fusarium culmorum and Fusarium oxysporum
Phthalic acid esterases	Thauera chlorobenzoica 3CB–1, Aromatoleum evansii KB740 , Gordonia sp. YC-JH1
Phthalate	Thauera chlorobenzoica
Polyhydroxyalkanoate (PHA)	Gracilibacillus, Enterobacter, and Bacillus

Regarding the chemistry of polyethylene (PE), it is notable that the carbon–carbon (C–C) backbone of PE is linear and extremely stable, which makes it resistant to degradation and poses a major obstacle to the biodegradation of plastic waste (Ghatge et al., 2020). Previously, it was discovered that over 60 marine bacteria from pelagic waters could break down low-density polyethylene (LDPE) when it served as a special carbon source. Based on the homology of the 16S rRNA gene sequence, three very effective isolates were identified (Bacillus pumilus M27, Bacillus subtilis H1584, and Kocuria palustris M16). These isolates also showed a higher percentage of LDPE loss. According to reports, plastic films consisting of polyvinyl alcohol and LDPE can be broken down by marine bacteria called Vibrio alginolyticus and Vibrio parahemolyticus [29].

Furthermore, it has been determined that other bacteria contribute to the breakdown of linear low-density polyethylene (LLDPE). Lysinibacillus sp. and Salinibacterium sp. were isolated and identified from the degradation experiment conducted in the microcosm. Interestingly, they were able to determine the function of the marine bacterial strain AIIW2 growth on the plastic surface by degradation experiments of PVC, LDPE, and HDPE [30].

The enormous molecular weight and strong structural stability of polystyrene (PS) make it widely thought to be nonbiodegradable. In aquatic situations, expanded polystyrene (EPS) can serve as a colonization habitat for a variety of microbes and algae, creating plastic biospheres (Syranidou et al., 2017; Zhao et al., 2023). Research reveals that, PS film was biodegraded by Bacillus paralicheniformis G1 (MN720578), which was found in sediments from the Arabian Sea at a depth of 3538 m. The strain degraded 34% of the PS film over just 60 days after being incubated. Additionally, its genome study sheds light on the underlying molecular causes of biodegradation (Andrady & Neal, 2009).

Also, exclusive research on marine microorganisms reported that numerous marine bacterial isolates, including those from Gordonia, Stappia, Mesobacillus, Alcanivorax, Flexivirga, Cytobacillus, Thioclava, and Thalassospira, shown the ability to degrade PS at rates ranging from 2.66% to 7.73% in a single month. The formation of C-O and C=O carbonyl groups suggests that an oxidation pathway is used in the breakdown of EPS. These marine microorganisms may be representatives of various marine ecosystems and thus have engaged in the removal of EPS wastes in marine mangrove environments [33].

5. Degradation of waste water

Microorganisms that can break down and extract azo colors from water hold promise for creating environmentally benign and economically viable methods of treating azo wastewater, despite its high salinity, toxicity, and volume. The ability of the marine bacterium Aliiglaciecola lipolytica to decolorize Congo Red (CR), a common azo dye in synthesized water, was investigated. The outcomes demonstrated that the bacteria could self-flocculate and undergo aerobic decolorization in a variety of settings. Extracellular polymeric substances (EPS) were shown to be the primary source of the dyes’ initial adsorption onto cells, after which roughly 46% of them underwent degradation. This breakdown was caused by co-metabolism with glucose and was aided by intracellular laccase and azoreductase. After the chromophore groups (C-N), azo linkage (-N=N-), and sulfonate groups (−SO3) were broken, the naphthalene rings disintegrated, reducing CR into smaller molecules. The bacteria released a large amount of EPS, particularly humic acid and protein-like substances in tightly bound EPS (TB-EPS), which improved the hydrophobicity of the cell surface and reduced electrostatic force, hence promoting dye adsorption and cell self-flocculation (Wang et al., 2020).

Among other pollutants, pesticides in waste water undergo chemical compositional alterations as a result of biotic and abiotic activities. The elimination of a particular pesticide, atrazine, has been deemed necessary and is causing increasing public health concerns. In order to solve this, scientists investigated the capacity and effectiveness of several marine bacterial isolates to break down atrazine. The goal of this research is to use powerful native marine bacteria, either with or without exogenous variations, to remediate and regulate the widespread atrazine pollution in the environment. The strains of Bacillus cereus ATCC 14,579 (E9), Bacillus pacificus MCCC 1A06182 (E7 and E8), and Bacillus paramycoides MCCC 1A04098 (E11 and E13) exhibited a very high biodegradation of atrazine with removal efficiency upto 97% (Ghazi Alattas et al., 2023).

Also, heavy metals released from tannery effluents causes heavy metal contamination in the surface water bodies. Therefore, Calcium-based adsorbents in conjugation with magnetosomes, procured from magnetotactic bacteria were attempted to remove heavy metals from tannery effluents. According to research, calcite crystals that were magnetically manipulated were able to successfully separate from the solution and remove Cr (III) and Ni(II) from the collected tannery effluent (Ali et al., 2018). The findings suggested that using magnetic calcite as an alternate adsorbent to remove heavy metals from tannery effluent would be useful. Therefore, large-scale cultivation of magnetotactic bacteria has been implemented in the recent days. Utilizing an electric field to promote Cr6+ removal in practical applications has presented a novel and cost-effective way for enhancing waste water treatment using magnetotactic bacteria (Vijayaraj et al., 2020).

Recently, two potent siderophore marine bacterial isolates were notable in efficiently reducing the pollutant load reduction under aerobic and anaerobic conditions. Marinobacter hydrocarbanoclasticus and Nitratireductor kimyeongensis were capable of the load of heavy metals (Chromium, sulphate, phosphate and nitrate). Also, the effectiveness of bioremediation was further supported by bioassay experiments using plant and animal models, where it was found that bioremediated wastewater had significantly lower toxicity when compared to untreated effluent due to higher seed germination, longer plants, and increased survival rates of Artemia nauplii. This research has posed an efficient clean-up strategy and removal of waste water (Vijayaraj et al., 2020)

Saline waste water treatment had a break-through when a pure flocculating marine bacterium, Psychrbacter aquimaris X3–1403 exhibited a good settleability. The EPS present in the bacterium promoted increased cell surface hydrophobicity, particle size and specific gravity. The self-flocculating mechanism of this bacterium provided a good performance in treatment of saline water tested at different salinity (Cho et al., 2018). Their mechanism of action is represented in Figure 4. Another bioflocculant, produced by Altermonas spp. CGMCC 10,612 were used in the application of dye waste water treatment. This bacterium attributes specific features such as, thermal stability, presence of nitrogen and oxygen groups promoting flocculation, and excellent decolourization stability promoting promising dye reduction in waste water (Mathivanan et al., 2021)

Figure 4. Self-flocculation mechanism of psychrobacter aquimaris X3–1403.

6. Application of marine microbial enzymes

The development of industrially relevant marine enzymes by metagenomics is an innovative and a potential approach. Due to their distinct characteristics, marine organisms have demonstrated themselves to be a novel source for the separation of industrial enzymes. Application of metagenomic tools in biotechnological applications has been critical by enhancing knowledge on effective enzyme selection protocol and providing a sequence-based description for worldwide marine ecosystems (Izadpanah et al., 2018). Compared to their homologs from animals, plants, or microbes, marine enzymes have better operating characteristics, and so are frequently used in industry. Therefore, these marine enzymes contribute many beneficial applications to the ecosystem. The application of several marine enzymes is represented in Table 2.

Table 2. Diverse applications of marine microbial enzymes

Marine enzymes	Applications
Lipase	Food industries, pharmaceutical industries, bioprospecting, paper production, organic synthesis
Protease	Pharmaceutical industries, food industries, bioprospecting, anti-inflammatory drugs
Alkaline protease	Detergents (Bacillus mojavensis)
Alginate lyases	Industrial, agricultural, medical applications
Agarases	Cosmetics
Chitinases	Compound synthesis
Carrageenases	Cosmetics and pharmaceutical industries
Cellulase	Textile and biofertilizers
Extremozymes	Antibiotics, compound synthesis
Xylanases	Fermentation in alcohol
Phytase	Food and dairy industries
Gluccanases	Dental and other healthcare

7. Chitinase

Chitooligosaccharides (COS), produced by chemical or enzymatic hydrolysis of chitosan and chitin, are water soluble and considerably less viscous than chitin and chitosan and exhibit a variety of biological properties, including prebiotic, antibacterial, antioxidant, and antihypertensive properties. An effective and environmentally benign alternative, enzymatic methods employ mild, localized, and controlled reaction conditions. Chitinase-producing bacteria from marine wastes are receiving more attention, and they are useful for lowering environmental risks through waste management and boosting the production of significant value-added products. As these marine bacteria can transform chitin into forms of carbon and nitrogen that are useful for biological processes, chitin can be recycled in the marine environment (Paulsen et al., 2016).

Chitinases and chitin oligomers produced by marine bacteria have drawn a lot of interest as prospective enzymes for use in a variety of industries, including waste management, biotechnology, agriculture, and industrial applications. Additionally, they have insecticidal, anti-fungal, anti-malarial, hypocholesterolemic, and anti-hypertensive qualities that are used to improve food quality (R. Singh et al., 2021). Marine sediment serves as a good place to evaluate the effectiveness of chitinolytic bacteria because very little accumulation of insoluble polymer is witnessed despite continual chitin production in the water column (Paulsen et al., 2019).

Recent analysis through genome walking revealed that, the novel 1251 bp chitinase gene (ChiT-7) was cloned from the metagenome of the mangrove tidal flat soil in Zhangzhou, Fujian Province, China. The 381 amino acid mature protein that the gene produced showed some sequence similarity (59% identity) to the GH18 chitinases that have been identified. In E. coli BL21 (DE3), the mature ChiT-7 protein was successfully produced. The following are characteristics that set ChiT-7 apart. ChiT-7 was shown to belong to the GH18 family by phylogenetic analysis and amino acid sequence alignment, however it differed from Chloroflexi, Laceyella putida, L. sacchari, and Paecilomyces chitinases by 59% (Kuan Li et al., 2020).

Due to their hydrolytic action on chitin, chitinolytic enzymes have gained interest recently on a global scale for their various biotechnological and therapeutic uses especially in the management of chitinous waste; as a result, they have the potential to play a key role in future green applications (Dukariya & Kumar, 2020).

8. L- asparaginase

A commonly known hydrolase, L-asparaginase (L-asparagine amidohydrolase, E.C. 3.5.1.1) is largely responsible for converting L-asparagine into L-aspartic acid and ammonia. Currently, microbial L-asparaginase formulations for biomedical uses supply one-third of the world’s need for antileukemia/antilymphoma drugs. L-asparaginases have been widely employed for anti-leukemia chemotherapy in acute lymphoblastic leukaemia, which is significantly greater than other therapeutic enzymes. Also, it has been used for the treatment of several lymphoproliferative illnesses and lymphomas, including acute lymphoblastic leukemia (ALL) and Hodgkin’s lymphoma (Cachumba et al., 2016).

L-asparaginase has been targeted for increased production due to its therapeutic significance. Since it is administered continuously throughout treatment, L-asparaginase, which is derived from terrestrial bacteria, has been linked to a number of adverse reactions, including allergy, pancreatitis, neurological disorders, bleeding, and thrombotic events like stroke. Reports indicate that marine samples, particularly seawater, which is saline in nature and chemically closer to human blood plasma, may be a good source of active asparaginase-producing microorganisms. It is anticipated that marine microorganisms may provide L-asparaginase with fewer side effects for humans. The FDA has approved L-asparaginase for the efficient treatment of lymph sarcoma and acute lymphoblastic leukaemia (Egler et al., 2016).

The food sector is another significant application for this enzyme, as it can be used to lower the acrylamide levels in commercial fried foods while preserving their quality in terms of color, flavor, texture, security, etc. Interestingly, l-asparaginase catalyzes the hydrolysis of l-asparagine, preventing the production of acrylamide by decreasing sugars in response with this amino acid Numerous marine microorganisms have been found to have L-asparaginase. Bacillus sp. and Pseudomonas sp. were the most prevalent bacteria found in the maritime sources of bacterial isolates. Additionally, multiple researchers have identified the possibility for L-asparaginase synthesis from a variety of marine actinomycetes (Izadpanah Qeshmi et al., 2018).

In a recent study, the impact of marine L-asparaginase on the synthesis of polyacrylamide was assessed. Up to 86% less acrylamide was present in potato chips after they were pretreated with thermostable and alkaline L-asparaginase from P. barengoltzii CAU904 (PbAsnase). Also, L-asparaginase from N. alba NIOT-VKMA08 reduced, or at least delayed, the production of polyacrylamide in reaction media, while polyacrylamide immediately solidified in the reaction mixture without the need for additional enzyme supplementation. According to reports, when L-asparaginase from Trichoderma viride sp. was incubated in fried potatoes that had already been treated with the enzyme, it showed very little activity. When the enzyme was incubated with fried potatoes that had not been treated, its activity reached extremely high levels, a behavior that the authors attributed to acrylamide mitigation [48 (Hadi et al., 2023).

9. Lipase

There are three major phyla that are actively involved in the production of lipases. Proteobacteria, Firmicutes and Bacteroidetes. These phyla are differentiated into nine genera consisted of Bacillus, Chryseomicrobium, Photobacterium, Pseudoalteromonas, Ruegeria, Shewanella, Solibacillus, Tenacibaculum and Vibrio. G. Lipases contribute 88.3% of their activity in the maritime environment. Interestingly, bacteria isolated from horse shoe crab and jelly fish are actively involved in lipase production (Navvabi et al., 2018). Penicillium oxalicum, Aspergillus flavus, and Streptomyces produce marine microbial lipases. These enzymes exhibit a wide range of substrate specificity and can actively hydrolyze various oils and organic solvents. Many of the lipases currently in use are employed in the manufacturing of medications, flavourings for food, and other industrial uses (Chandra et al., 2020).

Also, Bacillus cereus HSS isolated from the Mediterranean Sea exhibited efficient lipase production wherein treatment of oily waste water was carried out. The removal efficiencies were recorded as 87.63,90 and 94.7% for biological oxygen demand, total suspended solids, and oil and grease respectively. This can be further promoted for diverse applications. Additionally, the lipase activity of psychophilic bacteria from Antarctic seawater was examined. The 16S rRNA gene sequence analysis was used to determine which strain was the most promising. A genome-walking technique was used to establish the whole lipase gene, which was then expressed in E. coli to create a recombinant lipase with optimal activity at 20°C and the ability to break down C16 and C18 p-nitrophenyl esters, a characteristic of authentic lipases (Hassan et al., 2018).

The marine bacteria Oceanobacillus sp. PUMB02 produced a halotolerant thermostable lipase that was isolated and studied. This lipase showed excellent stability in a variety of circumstances, such as temperature, salinity, and pH. Response surface method-guided optimization was used to determine the optimal conditions for increased lipase production by Oceanobacillus sp. PUMB02. Higher production was achieved by evaluating components such as olive oil, sucrose, potassium chromate, and NaCl. The PUMB02 lipase’s capacity to disrupt biofilms was assessed and contrasted with the halotolerant lipase Lpc53E1, which was obtained from the metagenome of marine sponges. When used against possible food pathogens such Bacillus cereus MTCC1272, Listeria sp. MTCC1143, Serratia sp. MTCC4822, E.coli MTCC443, Pseudomonas fluorescens MTCC1748, and Vibrio parahemolyticus MTCC459, good biofilm disruption activity was seen with both lipases. This demonstrated the possible use of Oceanobacillus lipases in biofilm disruption techniques (Seghal Kiran et al., 2014).

Another study involved a lipase that was isolated from the marine bacteria Bacillus pumilus B106. Through the use of gene cloning and E. coli expression, this enzyme was described. Using p-nitrophenylacetate to improve the medium composition and achieving the ideal fermentation temperature of 40°C, an increase of 1.31 times the cell concentration and 3.54 times the lipase activity was observed. Notably, the enzyme was destroyed by 30–40% of methanol, ethanol, 2-propanol, and DMSO, but the enzymatic activity was enhanced by using 10–20% of methanol (Birolli et al., 2019).

Bacillus sonorensis and Paphia malabarica acquired from Kalbadevi estuary, Mumbai has been reported in the production of lipase. These lipases exhibit stability even till 60 ̊ C. Morever, these lipases exhibited maximum activity on interaction with detergents and surfactants. Lipase, when included in a detergent, is effective at removing oil stains from both natural and synthetic fabrics, according to washing trials and fatty acid release research. It can be concluded that lipases derived from marine sources are appropriate for use as an addition in detergent compositions (Ghatge et al., 2020).

10. Protease

Proteases are ubiquitous enzymes that are capable of carrying out the degradation of proteinaceous material by breaking the peptide bonds. It is important to understand that marine microorganisms are a key source of proteases with distinctive properties. Marine microbial proteases exhibit a high level of resistance to oxidising agents, metal ions, organic solvents, surfactants, and high temperatures. They are a crucial component for industrial applications because of their distinctive quality. The study of marine microbial proteases is yet relatively unexplored, but it is predicted to be a spectacular success in the near future. Bacillus subtilis obtained from the marine sediment of Eastern harbor of Alexandria exhibited active protease production at 40 ̊ C. The enzyme isolated from this bacterium has involved in the efficient removal of biological dyes including crystal violet, safranin and blood stains (Sivaperumal et al., 2018). Due to their resistance to chemicals and denaturing agents, thermostable proteases are crucial in the industrial and biotechnological fields. Thermozymes, which have been identified from organisms that are thermophiles, have characteristics of temperature stability and become active above 40 ̊ C. The use of thermophile proteases is advantageous because they react at high temperatures, increasing substrate concentrations and reaction rates. Thermotoga, Thermus, Thermococcus, Pyrococcus, Bacillus, and Sulfolobus are thermophilic family members that typically produce thermostable enzymes when isolated from marine microbes.

The literature also contained references to proteases derived from marine microorganisms. An alkaline protease from a Bacillus cereus that was recovered from crude oil in the Gulf of Khambhat, India, shown resistance to oxidizing ions, detergents (such as Tween 80 and Triton X-100), and organic solvents. Following purification, the enzyme demonstrated activity for hydrolyzing casein under ideal circumstances of 60°C and pH 8.0. In contrast to the increasing effect of Ca2+ and the deactivating or reducing action of the ions Cr3+, Zn2+, Cu2+, Hg2+, Pb2+, and Cd2+, ions like Li+, K+, Mg2+, and Ba2+ had no influence on the enzyme activity (Uttatree & Charoenpanich, 2018).

A different alkaline protease that could hydrolyze casein throughout a wide pH range (3–12) and temperature range (10–80°C) was identified from the marine bacteria Staphylococcus saprophyticus BUU1. The stability of this enzyme is supported by its resistance to oxidizing agents, bleaching agents, metal ions, surfactants, and apolar solvents, all of which were tested in conjunction with it (Chen et al., 2020).

Additionally, the marine Pyrococcus horikoshii-derived thermostable endopeptidase, a cysteine peptidase, is the first allosteric enzyme to exhibit negative cooperativity with Cl ions, emphasising its significance for medicinal advancements. [30]. Certain Pseudoalteromonas strains have had their protease output enhanced through strain mutagenesis or by optimizing fermentation conditions. P. arctica PAMC 21,717‘s extracellular protease synthesis was increased 15-fold by fed-batch fermentation and statistical optimization of mineral components. To increase the yield of its extracellular protease E423, pseudoalteromonas sp. CSN423 was exposed to UV irradiation for mutagenesis. This resulted in the production of a mutant strain that had a 5.1-fold greater protease yield. Researchers employed bovine artery powder, a cheap and effective inducer, by maximizing fermentation conditions and enhanced the enzyme output by more than twofold (Chen et al., 2020; Uttatree & Charoenpanich, 2018).

11. Amylase

Amylases are essential enzymes that break down internal glycosidic bonds in starch to create dextrins and oligosaccharides as their main byproducts. Because of the features of amylase that allow it to hydrolyze starch and the use of readily available, inexpensive raw materials, interest in amylase production has significantly expanded in recent years. Most commonly employed for the manufacture of α-amylase are P. furiosus, Bacillus stearothermophilus, Bacillus licheniformis, and Bacillus amyloliquefaciens. The hydrolysis of starch by α -amylase results in the production of fructose and glucose syrups (de Souza & de Oliveira Magalhães, 2010). From the surface to the deep sea, they are also found in a variety of taxa of marine extremophile archaea and bacteria, including Desulfurococcus sp., Pseudoalteromonas sp., Pyrococcus sp., Rhodothermus sp., and Thermococcus sp. An isolate of Geobacillus sp. from a geothermal vent has outstanding alpha-amylase stability between 80 ̊ C and 140 ̊ C. In the food business, amylases are also employed to produce glucose syrups, fructose and maltose, lower syrup viscosity, lessen juice turbidity, and ferment alcohol. Additionally, they work in the petroleum, textile, paper, detergent, chemical, and pharmaceutical industries (de Souza & de Oliveira Magalhães, 2010).

In a recent study, the Plackett-Burman statistical experimental technique was employed to examine the primary factors affecting the synthesis of α-amylase by marine S. rochei KR108310 strain HMM 13. The Box-Behnken design was used to further alter the most effective variables in order to enhance the production of enzymes. The resulting enzyme was refined and characterized; it was shown to be more active at higher pH and temperatures and to be enhanced by the addition of various metal particles, which made it a promising candidate for a variety of uses (Al-Agamy et al., 2021).

A new study isolated and characterized a new digestive α-amylase (BCA) that was recovered from the viscera of blue crabs. The enzyme was homogenized after the last purification stage. The enzyme has favorable biotechnological properties, including high specific activity, broad pH range stability, intriguing heat stability that was improved in the presence of starch, and an ideal temperature of 50°C. BCA degraded a variety of carbohydrates, resulting in the main end products of starch hydrolysis being maltose, maltotriose, and maltotetraose. This suggests that BCA may be used to make maltodextrin-rich, glucose-free syrups. Furthermore, the refined enzyme was effectively employed to enhance the antioxidant capacity of oat flour, a prospective application that might be expanded to include additional grains. This enzyme can be proposed to several industries due to its distinctive features (Maalej et al., 2021).

12. Useful resources from marine microorganisms

The untappped sources of marine microorganisms have been explored for their useful resources (Syranidou et al., 2017). A varierty of enzymes are regarded as crucial ecological elements in maritime habitats because of how well they function in biogeochemical processes.Due to their abundance, brown algae (Phaeophyceae) retain a unique position. For coastal regions, it is crucial for CO₂ removal and carbon storage. Alginate is a plentiful source of carbon in aquatic environments. Alginates with polymerization levels ranging from 2 to 25 are produced through the chemical, physical, or enzymatic degradation of alginate. Large volumes of alginates, which are used as nutrient sources by heterotrophic marine bacteria, are produced annually by a variety of oceanic algae. Alginate lyases have a lot of promise for use in the biofuel business, pharmaceutical sector, and environmental protection (Barzkar et al., 2022).

Also marine derived microorganisms have been involved in biocatalysis and biotransformation process. In order to obtain valuable molecules employing new effective biocatalysts for organic synthesis, marine-derived bacteria have been used in a variety of processes including kinetic resolution, deracemization, epoxidation, decarboxylation, hydroxylation, and hydrolysis reactions (Al-Agamy et al., 2021). For instance, entire cells of 26 strains isolated from marine sediments used cyclic -hydroxy ketones in a kinetic resolution (Birolli et al., 2019). It is interesting to know that, many of the secondary metabolites from marine-derived microorganisms are structurally hybrid molecules. Tetroazolemycins A and B, two novel oxazole-thiazole siderophores, were discovered in 2013 by Liu et al. from a deep-sea strain of Streptomyces olivaceus. Fe^3+, Cu^2+, and Zn²⁺ were just a few of the cations for which they displayed an attraction. In addition to three recognised chemicals, a chemical analysis of a culture extract of the sponge-derived fungus Alternaria sp. produced two new altenusin-thiazole hybrids, called altenusinoides A and B. The recognised compounds among them demonstrated COX-2 inhibitory activity as well as DPPH free-radical scavenging abilities (Beygmoradi & Homaei, 2017; Mohamed et al., 2021).

Meroterpenes and meroterpenoids are other often seen substances made by marine microorganisms. As shown below, they are hybrid natural products made by combining terpene or terpenoids moieties with other precursors, such as polyketide. They exhibit a wide variety of beneficial biological actions. Sesteralterin and four novel meroterpenes, tricycloalterfurenes A—D, were discovered through chemical analysis of the culture extract from the marine fungus Alternaria alternata k21–1, which was isolated from a marine alga. Several of them demonstrated phytoplankton-specific inhibitory action. In 2018, six novel meroterpenoids known as brasilianoids A—F were discovered in the Penicillium brasilianum sponge-associated fungus (Nazir et al., 2021). Among those, Brasilianoids B and C shown modest inhibitory action against any of the generation in LPS-induced RAW 264.7 macrophages, while brasilianoids A dramatically increased the expression of filaggrin and caspase-14 in HaCaT cells in a dose-dependent manner (Xu et al., 2017).

After several efforts, the application of marine compounds had hit the global market when the marine compound dolastatin (several units of the potent antimitotic agent monomethyl auristatin E) was introduced as a conjugate between a monoclonal antibody that targets the cell-membrane protein CD30, an antigen which is highly expressed in lymphoid tumors. This led to the development of brentuximab vedotin (Adcetris®), approved by The US Food and Drug Administration (Barreca et al., 2020). This kickstarted their application in several fields wherein representative marine materials used in tissue engineering and regenerative medicine as biopolymers and bioceramics because they have bioactive qualities. Around 30 drugs are undergoing preclinical or clinical studies. Sixteen out of the 20 marine anticancer drugs that are undergoing clinical trials come from microbiological sources. Examples include thiocoraline, which is used to treat various malignancies, and didemnin B (AplidineTM) (Ameri, 2014; Mostafa et al., 2020).

The marine organism-derived extracellular matrix (ECM), has been explored as a biomaterial and utilised to reconstruct tissues and improve biological processes. Sea cucumber was analysed to determine extracellular vesicle activity and their physiological role in the aquatic environment. When extracellular vesicles from sea cucumbers were used to treat the lipopolysaccharide (LPS)-infected macrophages, it became clear that they had the strongest suppressive power. This study demonstrated how extracellular vesicles from different marine animal species can be used in research to create high-value therapies from discarded marine wastes (Paulsen et al., 2019). Value added products from marine microorganisms is represented in Figure 5.

Figure 5. Value added products from marine microorganisms.

Numerous marine microorganisms are capable of degrading a wide range of food wastes while also producing value-added products. The marine thraustochytrid Aurantiochytrium sp. T66 can be cultivated on food waste hydrolysate for the mining of squalene and docosahexaenoic acid (DHA). Post-consumption food waste hydrolysate (PCFWH), which has glucose and fructose substrate generates more DHA. Also, Schizochytriumlimacinum SR21 produces more DHA due to the presence of the high quantity of glucose and fructose in sweet sorghum juice. Also, agricultural waste may be effectively degraded by cyanobacteria, which can then be used as compost as a biofertilizer. Agricultural wastes are employed as economical and less expensive sources for the synthesis of pectin lyase by the marine isolate Penicillium expansum RSW SEP1. This has been implemented in dyeing wool fibres by using extracted natural pigments as chlorophyll from green algae (Patel et al., 2020).

Moisturizing compounds like polysaccharides and fatty acids, that are frequently utilized in cosmetics, are produced by marine species. To moisturize skin, oil-in-water emulsions can contain algae-derived omega-6 polyunsaturated fatty acids, particularly C-18 linoleic acid and gamma-linolenic acid, which are found in the genus Phaffia, Rhodozyma, and Xanthophyllomyces. Also, unsaturated fatty acids are largely produced by marine microorganisms. Better than hyaluronic acid in cosmetics, the EPS of the Polaribacter sp. SM1127, isolated from Arctic kelp, has a good moisturizing capacity. When applied at moderate temperatures, this EPS significantly protects human skin fibroblasts and can be utilized as a moisturizing component in cosmetics (Ding et al., 2022).

Recently, there has been a lot of interest in marine microbial natural products (MMNPs) from many sources. A wide variety of MMNPs with antibacterial, anti-tumor, anti-inflammatory, and anti-cardiovascular activities seem to be produced by a variety of marine microorganisms. Metagenomics, genomics, combinatorial biosynthesis, and synthetic biology are examples of MMNPs. Thus, for a futuristic approach, a consideration of possible obstacles and prospects for MMNP research is required [72].

13. Bioeconomy of waste management using marine microorganisms

The conversion of the traditional system of using bioresources to sustainable ones has attracted significant interest across the globe. The process typically includes the use of biomass derived from waste produced by various businesses or resources from biological sources. The successful growth of the bioeconomy today reflects a global movement to guarantee the utmost safety and sufficient access to healthy food, raw materials, energy sources, and water, as well as their effective utilisation. Microorganism-based bioprocesses may contribute to the circular bioeconomy and the recycling of industrial waste (Dahiya et al., 2022).

A sustainable circular bioeconomy is remarkably advocated by valorizing waste or side streams into bioprocessing to produce value-added bioproducts from marine microorganisms. A circular bioeconomy, or low-carbon economy that minimizes greenhouse gas emissions, greatly contributes to the resolution of global issues like food security and environmental challenges. Therefore, there is significant potential for a sustainable green world with a waste biorefinery—circular bioeconomy plan, and it can be uplifted by the marine bioproducts (Leong et al., 2021).

In order to establish affordable and sustainable waste management operations, extensive monitoring data on waste generation are progressively being collected. In addition, free access to geographic data from several society registrations is now available. To provide more precise, real-time waste generation information that will serve as the foundation for trash management and collection, new data analytics techniques can be constructed on top of the data. In this study, a set of waste generation type profiles are created using a data-based method based on the self-organizing map (SOM) and the k-means algorithm. The outcomes demonstrate the possibility of cutting-edge data analytical techniques to generate more precise waste generation data [75]. The influenceof bioeconomy towards waste management is mentioned in Figure 6.

Figure 6. The concept of bioeconomy in waste management.

The bio-based circular economy, which closes the loop on raw materials including fresh or unprocessed resources, water, minerals, and carbon, uses one of the most important facilitation mechanisms called biorefining. It can be characterised as sustainable bioprocesses that effectively use biomass resources to create a variety of marketable products and metabolites (such as bioactive chemicals, lipids, proteins, and biomaterials). Moreover, waste biorefinery is given just as much attention, if not more, because it is a good waste management strategy. Bioprocesses that use waste materials to make biomaterials and biofuels can considerably reduce the need for fossil fuels as the production feedstock, preventing the depletion of all natural resources. By reducing carbon footprints, this strategy not only maintains the energy-environment nexus but also safeguards the ecosystem. Moreover, these bioprocesses can be integrated with other management tools, such wastewater treatment facilities [75 (Rotter et al., 2021).

Understanding how microorganisms are influenced by their environment and other microorganisms can be gained by observing and analysing the dynamics of marine microbial communities. Patterns that show community-level resilience and, frequently, seasonality have been discovered through the application of techniques that estimate microbial populations and their dynamics through time (Bioenergy, 2019).

The marine biosphere provides a diverse range of flora and fauna, serving as a significant natural resource for essential commercial-grade goods. Due to their structural and functional diversity, biosurfactants (BS) and bioemulsifiers (BE) are among the different bioactive chemicals that are gaining the most interest. Surface active molecules’ adaptable characteristics have a wide range of uses in many different industries. For the production of BS/BE and exopolysaccharides, marine microorganisms such as Acinetobacter, Arthrobacter, Pseudomonas, Halomonas, Myroides, Corynebacteria, Bacillus, and Alteromonas sp. have been investigated. The vast majority of the marine microbial world is still undiscovered because of the size of the marine biosphere. The identification of powerful marine microorganisms that produce BS/BE would increase the usage of environmentally friendly surface-active molecules and, ideally, lessen overall dependence on or the number of new applications focused on chemical synthetics (Li et al., 2018).

The shift to a bio-based circular economy that is sustainable calls for state-of-the-art technologies that balance environmental responsibility with economic growth. Only until the digitalization prospects are fully utilized will this shift be possible. Big data processing and digital techniques have already permeated the life sciences and typically hold enormous promise for a wide range of study fields. Even though state-of-the-art computer analyses of microbial metagenome data have emerged, bioinformatics’ full potential has not yet been fully realized. The use of digital twins in biocatalysis, enzyme cascades, and enzyme manufacturing are some of the future prospects for digitalization in marine microbiology. Digitalization offers a variety of options in computational biocatalysis, including the ability to simulate enzymes without the use of crystal structures as templates. The creation of custom enzymes from scratch that have better qualities than their natural counterparts and the creation of artificial enzymes that can catalyze reactions that are not feasible in nature could then be the following steps. With these opportunities, digitalization can be seen as a crucial piece in the puzzle that leads to a circular bio-based economy that is sustainable [79].

14. Challenges

The fields of omics, pharmacological analysis, and bioinformatics are driving scientific research trends and are regarded as basic resources for finding novel compounds and organisms that may be used in industrial settings. Techniques for the adjustment of growth conditions, harvesting and extraction procedures, together with recombinant techniques, are key to most industrial models with quick economic exploitation, notably in food and nutraceutical applications.

The vastness and mostly uncharted territory of the ocean frequently provide startling findings. The metabolic processes and adaption mechanisms of marine microorganisms differ greatly from those of terrestrial species due to the vast and diverse ocean environment. These pathways provide a wide range of naturally occurring compounds with distinctive structures, abundant biological activity, and enormous diversity. However, up until now, not much has been done to develop maritime resources. The most important challenges in waste management are to know the suitable microbes for microbial diversity and overcome the barrier existing from laboratory difficulties to oceanic disturbances. Therefore, it is important to enhance their survival and biodegradation capabilities in order to intensify their bioconversion rates.

Also, the marine microorganisms have been given less importance in both industry and academia. Identification and Isolation of unique marine microorganisms have been strenuous due to less standardization and optimization of microbial and molecular characterization. In these cases, maintenance of the microbial cultures is a herculean task as the oceanic conditions need to be mimicked in the laboratory. This may hinder the cell–cell communication that occur in the natural ecosystem influencing the growth.

Apart from the existing difficulties, nutrients play a vital role for the successful biodegradation of hydrocarbon pollutants especially nitrogen, phosphorus, for incorporation into biomass. When a major oil spill occurred in marine and freshwater environments, the supply of carbon was increased and the availability of nitrogen and phosphorus became the limiting factor in oil degradation. In marine environments, concentrations of available nitrogen and phosphorus in seawater generally are severely limited to microbial hydrocarbon and the availability of these nutrients within the area of hydrocarbon degradation is critical. Therefore, the application of marine microorganisms in various fields should be escalated on par with increasing technological developments (Birolli et al., 2019).

15. Future prospects

Waste management is considered one of the serious crises faced by the world in 21^st century. Many research communities are trying to find an efficient and sustainable solution for waste management. Bioremediation is considered to be a potential solution to tackle this waste management dilemma. Also, it is a more cost-effective and sustainable technique than any other methods available. The microbiological application against environmental pollution can be kindled through microbial biodegradation by optimizing and mimicking conditions such as temperature, pH, salinity, etc. These conditions are expected to enhance the biodegradation capacity of the microbes used for waste management. Due to the complex nature of the oceans, marine bacteria have developed advanced physiological and biochemical systems with which they uniquely adapt to extreme habitats and various unfavorable environmental conditions. They have also been reported to amplify the bioremediation of hydrocarbons, plastics, heavy metals, and dye degradation. So, marine microorganisms have been proved to be promising over terrestrial microorganisms (Sivaperumal et al., 2018). Additionally, a diverse microbial consortium is found to be more effective in the degradation and detoxification of waste than that of the community of a single microbe (Edet et al., 2023). However, the microbial diversity in the marine environment is yet to be explored. The integration of nanotechnology and aerobic degradation of microbes is also considered to be a potential measure of wastewater treatment (Crisafi et al., 2022a).

Apart from these, there are specific factors affecting the metabolism of toxic substances inside microbial systems, their growth parameters and biodegradation kinetics. Therefore, these parameters should be explored systematically and should be upgraded to the existing bioremediation techniques. Also, a strategy that involves the recovery of economically important by-products from the process should be implemented. The collected wastes should be used as raw materials for the production of value-added products for sustainable development (Izadpanah et al., 2018). Therefore, a diverse and balanced microbial consortium should be designed. The researchers should focus on improving the biodegradation time by marine microorganisms that stands apart from current bioremediation strategies.

16. Conclusion

Efficient and sustainable management of waste is one of the greatest challenges faced by the humanity. The impact of inappropriate management of waste results in disruption of ecosystem, biodiversity and economic development. Various applications of marine microorganisms like plastic waste degradation, wastewater management, hydrocarbon bioremediation open a wide world of opportunities towards waste management. Since marine microbes can produce substances that can inhibit attachment, microorganism growth, and/or cell–cell communication, in addition to the chemical components necessary for biofilm production, they present a promising new source of non-toxic compounds with sustainable anti-biofouling/anti-biofilm properties. Unquestionably, our understanding of the field of microbial metabolites has substantially advanced over the past many years, but there are still many steps to acquire a greater understanding about the potential of marine microbial metabolites. The timing of our discovery of marine microorganisms potential has made its mark in a promising scientific period. The quest for bioactive metabolites, which can overcome numerous challenges and impediments for the oceanic industries as well as many other industrial systems, must receive special attention in order to fully investigate the natural anti-fouling and potential of marine bacteria. As we are far away from achieving this goal, there should be more research and understanding on the marine microorganisms, its degradation capacity and novel approaches to identify the suitable organisms and enhance its capability.

Acknowledgements

The authors are thankful to Vellore Institute of Technology, Vellore for providing the necessary facilities to carry out this research.

Disclosure statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article.

Additional information

Notes on contributors

K Suthindhiran

K. Suthindhiran conceptualized the work on waste management using marine microorganisms and performed a formal analysis of every step. The project administration and concerns regarding the resources were provided by Dr. K. Suthindhiran. Ms. M. Haripriyaa proceeded with the acquisition of data for all the analysis. Ms. M. Haripriyaa was involved in manuscript preparation followed by drafting the work. After a series of critical evaluations, the raw data was converted into a manuscript, which was overseen and validated by Dr. K. Suthindhiran.