Cutinase-like enzyme from the yeast Cryptococcus sp. strain S-2 hydrolyzes polylactic acid and other biodegradable plastics

Abstract

A purified lipase from the yeast Cryptococcus sp. strain S-2 exhibited remote homology to proteins belonging to the cutinase family rather than to lipases. This enzyme could effectively degrade the high-molecular-weight compound polylactic acid, as well as other biodegradable plastics, including polybutylene succinate, poly (epsilon-caprolactone), and poly(3-hydroxybutyrate).

FIG. 1.

Comparison of conserved amino acid motifs in cutinases. P11373, Colletotrichum gloeosporioides; P30272, Magnaporthe grisea; P41744, Alternaria brassicicola; P29292, Ascochyta rabiei; P52956, Aspergillus oryzae; P00590, Fusarium solani; Q00298, Botrytis cinerea; Q10837, Mycobacterium tuberculosis; CLE, Cryptococcus sp. strain S-2 CLE. Three residues belonging to the catalytic triad are indicated by boldface type. A nucleophilic serine is located in a highly conserved GXSXG pentapeptide consensus motif.

FIG. 2.

Degradation of PLA (A), PBS (B), and PCL (C) by CLE and proteinase K. PLA degradation (A) was carried out with enzyme concentrations of 400 μg/ml (▵) and 0.8 μg/ml (▴) for proteinase K from T. album or 0.8 μg/ml for CLE from Cryptococcus sp. strain S-2 (⧫). A reaction mixture incubated without any enzyme served as the control (×). Degradation of PBS (B) and degradation of PCL (C) were carried out with a CLE concentration of 8 ng/ml.