Cloning and Sequencing of a Poly( dl -Lactic Acid) Depolymerase Gene from Paenibacillus amylolyticus Strain TB-13 and Its Functional Expression in Escherichia coli

Abstract

ABSTRACT The gene encoding a poly( dl- lactic acid) (PLA) depolymerase from Paenibacillus amylolyticus strain TB-13 was cloned and overexpressed in Escherichia coli . The purified recombinant PLA depolymerase, PlaA, exhibited degradation activities toward various biodegradable polyesters, such as poly(butylene succinate), poly(butylene succinate- co -adipate), poly(ethylene succinate), and poly(ε-caprolactone), as well as PLA. The monomeric lactic acid was detected as the degradation product of PLA. The substrate specificity toward triglycerides and p -nitrophenyl esters indicated that PlaA is a type of lipase. The gene encoded 201 amino acid residues, including the conserved pentapeptide Ala-His-Ser-Met-Gly, present in the lipases of mesophilic Bacillus species. The identity of the amino acid sequence of PlaA with Bacillus lipases was no more than 45 to 50%, and some of its properties were different from those of these lipases.