A cold-adapted polyurethane-degrading lipase from the gut bacterium of plastic-eating superworms

Enzymatic recycling has been proposed as an alternate strategy to polyurethane (PU) waste management. However, the bulk of previously known PU-degrading enzymes were classed as thermophilic or mesophilic enzymes, with cold-adapted enzymes being uncommon. Here, we identified PSLA, a cold-adapted lipase from Pseudomonas sp. BIT-r11, a strain isolated from the gut of plastic-eating superworms. PSLA retained activity at 0 °C, and exhibited a low optimal temperature (T_opt) of 15 °C, a melting temperature (T_m) of 35.5 °C, and a pronounced temperature gap (T_m-T_opt) of 20.5 °C, features characteristic of a cold-adapted enzyme. Under optimal conditions (15 °C, pH 7.0), PSLA degraded 49.56 ± 3.74% of a dispersed polyester-PU emulsion (Impranil® DLN-SD) within 15 min and caused 1.20 ± 0.03% weight loss of solid polyester-based PU foam over 5 days. Structural comparison and molecular dynamics (MD) simulations suggest that a truncated C-terminal region is associated with increased terminal flexibility at low temperature. This flexibility may facilitate catalytically competent substrate binding, as reflected by more stable maintenance of a near-attack geometry between S207 and the substrate in simulations, as well as a lower apparent K_m and higher catalytic efficiency at 15 °C than at 30 °C. Together, these structural and kinetic features provide a plausible mechanistic basis for the cold-adapted PU-hydrolyzing activity of PSLA. This work expands the enzyme toolbox for low-temperature PU biodegradation and provides a starting point for developing PU biotransformation strategies under cold environmental conditions.