Optimized enzymatic PLA hydrolysis by a recombinant fungal cutinase: A step towards a closed PLA cycle

Polylactide (PLA) occupies the first position in the global production market of bioplastics, generating a large amount of waste. Cutinases have high potential to depolymerize plastic polyesters like PLA, since cutin, their natural substrate, is structurally similar. Here, the cutinase secreted by Fusarium solani (FsC) was heterologously produced in high yields, and its hydrolytic efficiency on PLA polymers of different stereochemistry, crystallinity, and polymerization degree was evaluated. Under the conditions tested, FsC proved to be enantioselective, with poly(D,L-lactic acid) (PDLLA) as its best substrate and no activity on poly(L-lactic acid) (PLLA). The hydrolysis of PDLLA was optimized by Response Surface Methodology (p-value <0.0001). After optimization, over 8 g/L of lactic acid were recovered from 10 g/L PDLLA in 15 h at 50 °C. This outstanding performance highlights the potential of FsC for its further improvement through computational design, with a focus on broadening its activity range or substrate versatility.