Microbial Degradation of Plastics

Environmental degradation of plastics takes a long time. The breakdown of plastics generates smaller bits of polymers called microplastics. This kind of particle accumulates in plants and animals, resulting in changes in metabolism. Therefore, the release of plastics into the environment is considered a serious environmental issue. The degradation of plastic polymers depends on the breakdown of carbon–carbon bonds, which requires high energy, so environmental degradation of plastics is difficult. However, microbial action has been found to accelerate the decomposition of plastics. It is reported that more than 40 species of bacteria belonging to the classes firmicutes and proteobacteria degrade various plastic composites. Aspergillus sydowii and Penicillium chrysogenum fungi are also reported to assist in the degradation of plastics in the environment. The initial step of microbial degradation of plastics is the breakdown of long-chain polymers into low-molecular-weight oligomers, which later assimilate into microbial cells or are converted into carbon dioxide. The presence of exoenzymes such as depolymerase helps microbes to break plastics. Hydroxylase genes present in microbes such as alkB, alkB1, and alkB2 were found to enhance the degradation of plastics. Thus manipulating the microbial genome also offers promising strategies for the ecofriendly breakdown of plastic contaminants in the environment.