Molecular mechanisms of plastic biodegradation by the fungus Clonostachys rosea

Microbial degradation provides an avenue for the remediation of select plastic polymers contributing to the urgent environmental problem of global plastic pollution. We demonstrate the degradation of polycaprolactone (PCL) by Clonostachys rosea and elucidate its underlying molecular mechanisms. We constructed the genome of this fungal strain and monitored changes in gene expression when exposed to PCL. Twelve genes linked to PCL degradation were found in the genome of C. rosea, and some of them were upregulated in the presence of the plastic, including genes coding for two cutinases. We heterologously expressed the enzymes coded by both genes and confirmed their activity against PCL polymers. We also demonstrate that one of the enzymes was active against polyethylene terephthalate (PET) polymers. Glucose inhibited the expression of both genes, completely halting the plastic biodegradation process, possibly serving as a preferred and readily metabolisable carbon source compared with PCL. We confirm the presence of key metabolic pathways linked to PCL degradation in C. rosea, including fatty acid degradation, providing further evidence of the mechanisms central to plastic biodegradation.