Biodegradation of Wheat Straw/PLA Composites by Four Kinds of Microorganisms

ABSTRACT

In order to compare the degradation of PLA composites by different microorganisms, and reveal the degradation mechanism. Actinomyces israelii, Aspergillus niger, Trichoderma harzianum and Phanerochaete chrysosporium were selected to degrade PLA composites. The weight loss, functional groups, thermal properties and crystallinity of the PLA composites before and after degradation were analyzed. The results indicated that A. israelii and A. niger had the strongest ability to degrade the composites, and the weight loss of the PLA composites reached 7.14% and 6.99% respectively after degradation for 28 days, which were significantly higher than that of the control treatment. According to the characterizations, it was found that the degradation was mainly hydrolysis by the microorganisms and their protease and lipase. Microbial degradation would lead to cracks and dents on the surface of the samples, and increase their contact area with microorganisms, thus accelerating the degradation rate. A. israelii and T. harzianum were more inclined to degrade the PLA in the composites during microbial degradation. Microbial degradation destroyed the crystalline region of the composites, which made they easier to degrade. The results would be helpful to explore the microbial degradation mechanism of PLA composites, and promotes its application in different fields.

摘要

为了比较不同微生物对聚乳酸复合材料的降解，揭示降解机理. 选择以色列放线菌、黑曲霉、哈茨木霉和黄孢Phanerochete降解聚乳酸复合物. 分析了降解前后PLA复合材料的重量损失、官能团、热性能和结晶度. 结果表明，以色列曲霉和黑曲霉对复合材料的降解能力最强，降解28天后PLA复合材料的失重率分别达到7.14%和6.99%，明显高于对照处理. 根据表征，发现降解主要是微生物及其蛋白酶和脂肪酶的水解. 微生物降解会导致样品表面出现裂纹和凹痕，并增加其与微生物的接触面积，从而加快降解速度. A.israelii和T.harzianum在微生物降解过程中更倾向于降解复合材料中的PLA. 微生物降解破坏了复合材料的结晶区域，使其更容易降解. 研究结果有助于探索聚乳酸复合材料的微生物降解机理，促进其在不同领域的应用.

KEYWORDS:

• Biodegradable polymer
• PLA composites
• degradation
• microorganisms
• Actinomyces israelii
• Aspergillus niger
• Trichoderma harzianum
• Phanerochaete chrysosporium

关键词:

• 可生物降解聚合物
• PLA复合材料
• 降解
• 微生物
• 衣氏放线菌
• 黑曲霉菌
• 哈茨木霉菌
• 黄孢原毛平革菌降解

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Xicun Chai performed the experiments and wrote the manuscript. Chunxia He and Yutao Liu conceived the idea and designed the experiments, and revised the manuscript. Other authors helped to correct the manuscript.

Highlights

• The degradation of PLA composites by four kinds of microorganisms was compared in this study.

• Actinomyces israelii and Aspergillus niger had strong ability to degrade PLA composites.

• Actinomyces israelii and Trichoderma harzianum were more inclined to degrade the PLA in the composites.

• Hydrolysis of the PLA composites by microorganisms and their proteases and lipases can significantly reduce the crystallinity of the PLA composites.

Additional information

Funding

This work was financially supported by the Fundamental Research Funds for the Central Universities, Grant Number: XUEKEN2022010; Ministry of science and technology of the People's Republic of China, Grant Number: 2019YFC1906104; Department of science and technology of Jiangsu Province, Grant Number: BE2019326.