Biodegradation of Microplastic Using Bacterial Cultures

Plastics are large molecular-weight organic polymers, commonly derived from different petrochemicals. There is a considerable increase in the global demand for plastics because of the ease of processing into various products used for packaging, handling, and storage of materials. There are many uses for various plastics such as polyolefin, polyester, polyvinyl chloride (PVC), polystyrene (PS), polyamide, ethylene vinyl alcohol, polyethylene (PE), polycarbonate, polypropylene (PP), polyurethane (PU), and polyethylene terephthalate (PET) in daily living. Microplastics are tiny plastic particles defined as plastics less than 5 mm in diameter. They are of two types, the first being primary microplastics which are tiny particles intended for commercial use in cosmetic products, and microfibers shed from textiles and fishing nets. Secondary microplastics are particles generated by the breakdown of bigger plastic items exposed to abiotic factors such as the sun’s rays and ocean waves. However, considering the rate of degradation or non-biodegradability of these organic polymers, they turn out to be a major environmental threat. They are highly stable and therefore do not enter into the degradation cycle of the biosphere easily. Degradation of plastics using physical and chemical methods may lead to innumerable environmental hazards. Microorganisms break down microplastics by producing intracellular or extracellular enzymes that turn long-chain polymers into oligomers and monomers that are then used by microbial cells. Some recent studies show that Pseudomonas sp. Ideonella sakaiensis, Klebsiella pneumoniae, Bacillus sp., Paenibacillus sp., Bacillus siamensis, Desulfotomaculum nigrificans, Alcaligenes sp. are some of the predominant bacterial species capable of degrading plastics.