Identification and Characterization of a Novel Thermostable GDSL Lipase LipGt6 from Geobacillus thermoleovorans H9

Abstract

Lipases are versatile biocatalysts for various biological reactions. In the detergent industry, lipases must exhibit high activity in environments with high temperature, high pH values, metal ions, and organic solvents. Therefore, researchers are intensively searching for more stable and efficient lipases. A new thermophilic lipase, LipGt6, was identified in Geobacillus thermoleovorans H9, a new thermophilic strain isolated from ultrahigh-temperature compost. A structural model of LipGt6 was constructed using an esterase from Geobacillus thermodenitrificans as a template, and site-directed mutagenesis confirmed the predicted active site residues. LipGt6 exhibited the highest activity towards medium- and long-chain fatty acids (C8–C14), and the optimum temperature and pH were 50 °C and 9.0, respectively. LipGt6 was found to be thermostable up to 70 °C. In the presence of 1% H2O2 and sodium deoxycholate, LipGt6 retained 70 to 75% relative activity. These findings reveal that LipGt6 is potentially useful for the industrial production of detergent. Based on comparison of the amino acid sequences, the enzyme belongs to a new subfamily called lipolytic enzyme family II. The catalytic residues Ser and His were more critical than Asp, and the Asp221 catalytic residue is not likely critical for the lipolytic reaction of LipGt6.