Discovery and characterizaton of a novel lipase with transesterification activity from hot spring metagenomic library

Abstract

A new gene encoding a lipase (designated as Lip-1) was identified from a metagenomic bacterial artificial chromosome(BAC) library prepared from a concentrated water sample collected from a hot spring field in Niujie, Eryuan of Yunnan province in China. The open reading frame of this gene encoded 622 amino acid residues. It was cloned, fused with the oleosin gene and over expressed in Escherichia coli to prepare immobilized lipase artificial oil body AOB-sole-lip-1. The monomeric Sole-lip-1 fusion protein presented a molecular mass of 102.4kDa. Enzyme assays using olive oil and methanol as the substrates in petroleum ether confirmed its transesterification activity. Hexadecanoic acid methyl ester, 8,11-Octadecadienoic acid methyl ester, 8-Octadecenoic acid methyl ester, and Octadecanoic acid methyl ester were detected. It showed favorable transesterification activity with optimal temperature 45°C. Besides, the maximal biodiesel yield was obtained when the petroleum ether system as the organic solvent and the substrate methanol in 350mmol/L (at a molar ratio of methanol of 10.5:1) and the water content was 1%. In light of these advantages, this lipase presents a promising resource for biodiesel production.