Microbial degradation of microplastics by enzymatic processes: a review

Microplastics contamination is becoming a major concern worldwide. More than 1 million seabirds and 100,000 sea animals have died due to plastic contamination. In addition, plastic particles have been found in juvenile turtles. Statistical data on plastic pollution indicate that this is a serious issue. Due to their small size, microplastics have a large surface area and have more ability to absorb into biological cells. The hydrophobic surface of microplastics attracts co-contaminants such as heavy metals, pharmaceutical toxicants, flame retardants, and other plasticizers, which can then enter biological organisms. Microplastics are usually recalcitrant in the environment, causing microplastics to be transported along the food chain, with humans as the final consumer. Research has been conducted to evaluate the best way to treat and remediate microplastic pollution. Research on microplastic degradation is focused on biological and non-biological approaches. To date, microorganisms such as algae, fungi, and bacteria have attracted the attention of scientists as a tool for microplastic treatment. The degradation of microplastics is closely related to the enzymatic reactions produced by the microorganisms. Here we review microplastics degradation through enzymes from the microorganism’s perspective. We present the enzymes that have been isolated from microorganisms for specific microplastics; the mechanisms of microplastics degradation by various enzymes; and the types of microplastics for which degradation mechanisms remain unclear.