https://orcid.org/0000-0001-8119-0165
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ABSTRACT
New possibilities for sustainable and climate-friendly plastic production are urgently needed. One degradable alternative could be polyhydroxybutyrate naturally produced out of CO2 via photosynthesis within cyanobacteria. Therefore, the polyhydroxybutyrate production of the so far little investigated polyhydroxybutyrate overproducing Synecho-cystis sp. PCC6714 mutant Mt_a24 should be further increased. The impact of reducing the exopolysaccharide production on the polyhydroxybutyrate yield was examined by knocking the exoD gene out. The generated transformants KOexoD#4 and KOexoD#65 were compared to the control strain under standard and nutrient limiting cultivation conditions regarding their growth, glycogen, polyhydroxybutyrate and exopolysaccharide production. Whereas the growth of all three strains was comparable under standard conditions, only minor differences could be detected under limited conditions. An increase of polyhydroxybutyrate could be observed in both transformants (KOexoD#4: 1.17-fold, KOexoD#65: 1.26-fold) under limited conditions. The exopolysaccharide production was increased in both transformants under standard cultivation conditions, showing a strong increase of soluble exopolysaccharides. In contrast, during limitation, the soluble exopolysaccharides decreased in all cultures whereas the tightly bound exopolysaccharides fraction strongly increased. Hence, the influence of limiting medium, and connection to the energy storage pathways could be shown as well as the great potential of Mt_a24 as a sustainable production system for polyhydroxybutyrate.
Acknowledgments
We thank the members of the research group AG Biosciences at the University of Applied Sciences Upper Austria for the helpful discussions.
This work was supported by the FFG under Grant [874108].
We thank the Technische Universität Wien for funding the doctoral college “bioactive”.
Disclosure statement
No potential conflict of interest was reported by the authors.
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Notes on contributors
Sandra Mittermair
Sandra Mittermair did her master degree in bio- and environmental technologies at the University of Applied Sciences Upper Austria, Austria, and is a research associate at the University of Applied Sciences Upper Austria, Austria, working in the fields of molecular biotechnology.
Juliane Richter
Juliane Richter is a biologist, did her PhD at the Friedrich-Alexander-University in Erlangen, Germany, and is now working as a Post-Doc at the University of Applied Sciences Upper Austria, Austria, in the fields of molecular biotechnology.
Philipp Doppler
Philipp Doppler is a PhD student within the doctoral college “bioactive” at the Institute of Chemical, Environmental and Bioscience Engineering at Technische Universität Wien.
Kevin Trenzinger
Kevin Trenzinger is a master student in bio- and environmental technologies at the University of Applied Sciences Upper Austria, Austria.
Cecilia Nicoletti
Cecilia Nicoletti did her master degree in chemical engineering at the University of Calabria, Italy, and is working as a research associate at the University of Applied Sciences Upper Austria, Austria, in the fields of bioprocess engineering.
Christian Forsich
Christian Forsich is a chemist and works as a research associate at the University of Applied Sciences Upper Austria, Campus Wels in the field of Materials Technology.
Oliver Spadiut
Oliver Spadiut is associate professor at the Institute of Chemical, Environmental and Bioscience Engineering at Technische Universität Wien.
Christoph Herwig
Christoph Herwig is a bioprocess engineer from RWTH Aachen and the head of the institute of Biochemical Engineering at Technische Universität Wien.
Maximilian Lackner
Maximilian Lackner is a scholar and entrepreneur with experience in the polymer industry and in bioplastics in particular.