Department of Biotechnology, The Neotia University, Sarisha, West Bengal, 743368, India.
Arch Microbiol. 2020 Oct;202(8):2117-2125. doi: 10.1007/s00203-020-01926-8. Epub 2020 Jun 6.
Plastics composed of polyethylene are non-biodegradable and are mostly harmful to the environment. Literature studies documented that the extent of microbial degradation of low-density polyethylene (LDPE) seems to be insufficient and the underlying mechanisms of such degradation remain unexplored. In the present study, efforts were given to degrade LDPE by a recently isolated bacteria Enterobacter cloacae AKS7. Scanning electron microscopic (SEM) image, tensile strength, and weight loss analysis confirmed the efficient degradation of LDPE by AKS7. To investigate the mechanism, it was observed that with the progression of time, the extent of microbial colonization got increased considerably over the LDPE surface. It was also observed that the organism (AKS7) gradually increased the secretion of extracellular polymeric substances (EPS) suggesting the formation of efficient biofilm over the LDPE surface. Furthermore, to comprehend the role of cell-surface hydrophobicity towards biofilm formation, two mutants of AKS7 were screened that showed a considerable reduction in cell-surface hydrophobicity in contrast to its wild type. The result showed that the mutants revealed compromised LDPE degradation than wild-type cells of AKS7. Further investigation revealed that the mutant cells of AKS7 were incapable of adhering to LDPE in contrast to wild-type cells. Thus, the results demonstrated that the cell-surface hydrophobicity of AKS7 favors the development of microbial biofilm over LDPE that leads to the enhanced degradation of LDPE by AKS7. Therefore, the organism holds the assurance to be considered as a promising bio-remediating agent for the sustainable degradation of polythene-based hazardous waste.
由聚乙烯制成的塑料是不可生物降解的，对环境大多有害。文献研究表明，低密度聚乙烯（LDPE）的微生物降解程度似乎不足，其降解的潜在机制仍未被探索。在本研究中，我们努力通过最近分离出的肠杆菌（Enterobacter cloacae）AKS7 来降解 LDPE。扫描电子显微镜（SEM）图像、拉伸强度和重量损失分析证实了 AKS7 对 LDPE 的有效降解。为了研究其机制，我们观察到随着时间的推移，微生物在 LDPE 表面的定殖程度显著增加。我们还观察到该生物体（AKS7）逐渐增加了细胞外聚合物物质（EPS）的分泌，表明在 LDPE 表面形成了有效的生物膜。此外，为了理解细胞表面疏水性对生物膜形成的作用，筛选了 AKS7 的两个突变体，它们的细胞表面疏水性与野生型相比显著降低。结果表明，与野生型细胞相比，突变体的 LDPE 降解能力较差。进一步的研究表明，与野生型细胞相比，AKS7 的突变体细胞无法粘附在 LDPE 上。因此，结果表明 AKS7 的细胞表面疏水性有利于微生物生物膜在 LDPE 上的发展，从而增强了 AKS7 对 LDPE 的降解。因此，该生物体有望成为一种有前途的生物修复剂，用于可持续降解基于聚乙烯的危险废物。
