Biochemical characterization of a novel feruloyl esterase from Penicillium piceum and its application in biomass bioconversion

Abstract

A putative feruloyl esterase (FAE) was successfully cloned from the genomic DNA of Penicillium piceum and expressed in E. coli. The deduced internal amino acid sequence of the novel FAE was found to have 56% sequence identity with FAE from Aspergillius flavus and was designated as PpFAE. PpFAE contained the conserved region flanking the characteristic G-X-S-X-G motif of a serine esterase, suggesting a FAE function for the protein. Substrate specificity profiling revealed that PpFAE was a type C FAE. The optimum temperature and pH for PpFAE were 70°C and 3.0, respectively. PpFAE was very stable under a pH range of 3.0–5.0 (>96% of maximum enzymatic activity) and displayed thermostability with thermal denaturing half-lives of 220min at 70°C and 150min at 60°C. Supplementation with low doses of PpFAE (120μg/g substrate) increased glucose yields released from corn stover, wheat bran, corn cob, and cassava stillage residues by 68.8%, 38.6%, 15.6%, and 20.0%, respectively. Supplementation with PpFAE could break down the intermolecular ester bonds that cross-link lignin with hemicellulose, effectively increasing the Xyl/Ara ratio and decreasing hydrogen bond intensity of the crude biomass.