Growth associated degradation of aliphatic-aromatic copolyesters by Cryptococcus sp. MTCC 5455

The degradation of aliphatic-aromatic copolyesters, poly[(butylene succinate/terephthalate/isophthalate)-co-(lactate)] (PBSTIL) and poly(butylene adipate co-terephthalate) (PBAT) under mesophilic conditions was investigated using the yeast, Cryptococcus sp. MTCC 5455. Complete degradation of PBSTIL and PBAT films was observed at 25 °C within 96 and 216 h, respectively. Lipase was produced during the course of degradation and the encoding gene was expressed in Escherichia coli BL21 (DE3). The production of lipase was enhanced by cumulative induction with 0.1 mM IPTG and 1.5 mM lactose for 24 h at 25 °C, which resulted in a maximum lipase activity of 27.75 ± 1.0 U/mL. Spectral studies of the degraded polymeric films confirmed the hydrolysis of ester bonds by the lipase. Scanning electron microscopy revealed the formation of cracks and holes on the surface of the polymeric films during degradation. The results indicated the feasibility of the process towards degradation of polymeric waste at ambient temperatures within a short period of time.