How microbes can degrade plastic?

With the rapid modernization and development of human society, there has been a very sharp increase in the demand of plastic- based products. Plastic is one of the most vital man- made products that has been produced in huge quantity and is used widely for different purposes in our everyday life. Question may arise why nonbiodegradable plastics are not degradable and why biodegradables are degradable? Microbial/biochemical degradation is a new concept in which some live microorganisms are used, which produces some biologically active enzymes to degrade the polymers, and these microorganisms use these polymers as carbon and energy sources. Microorganisms such as bacteria and fungi are involved in the degradation of plastics. The biological degradation of polymeric substances is a complex process involving several subsequent steps induced by the action of enzymes. During degradation, enzymes from microorganisms break down complex polymers yielding short chains or smaller molecules that are smaller enough to pass the semipermeable outer bacterial membranes and then to be utilized as carbon and energy sources [2]. This initial process of polymer breaking down is called depolymerization and the degradative pathways are often determined by the environmental conditions. The most important type of enzymatic polymer cleavage reaction is hydrolysis. Generally, the biological degradation of polymeric substances is influenced by the presence of enzymes and microorganisms, biotic availability of the polymeric structure and appropriate abiotic factors.