Location: Bioproducts ResearchTitle: Hydrolysis of ferulic acid in corn fiber by a metagenomic feruloyl esterase
Submitted to: BioResources
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2020
Publication Date: 12/10/2020
Citation: Wong, D., Chan, V.J. 2020. Hydrolysis of ferulic acid in corn fiber by a metagenomic feruloyl esterase. BioResources. 16(1):825-34.
Interpretive Summary: Corn fiber is a byproduct of wet-milling process. The corn-ethanol industry produces about 6.4 x 104 tons of corn fiber yearly, mostly used for animal feed. Corn fiber is highly recalcitrant due mostly to the hemicellulose fraction, which has a complex structure of heteroxylan. There have been efforts to characterize the remaining (non-degraded) oligosaccharides of heteroxylan that are resistant to mild acid pretreatment and simultaneous saccharification and fermentation (as used in corn ethanol production). The recalcitrant corn fiber hemicellulose can be ascribed to feruloylation of the side units and/or backbone of the xylan structure, which have not received much attention in biomass conversion studies. The present report describes enzymatic degradation of corn fiber using a metagenomic ferulic acid esterase and its synergistic action with added endo-xylanase.
Technical Abstract: A feruloyl esterase (FAE) gene was isolated from rumen microbial metagenome consisted of 774 bp encoding 258 amino acid residues. The gene was subcloned into pET 32b vector, expressed in E. coli, and the enzyme purified in active form. Homology modeling showed that the FAE contained the catalytic triad composed of Ser111 His236Asp208, and a classical Gly71-X-Ser73-X-Gly75 nucleophile motif commonly found in esterases. Under optimum pH and temperature (pH 7.0, 40oC), 1 nmole FAE catalyzed the release of 19.75±0.24 'g ferulic acid from 100 mg corn fiber in 1 hr, equivalent to 3.5% of ferulic acid present in saponified corn fiber. Addition of GH10 endoxylanase (EX) to 0.5 nmole ferulic acid enhanced the yield by a 5% increase in ferulic acid release. Liquid hot water pretreatment of CF enhanced the FAE-catalyzed hydrolysis of FA by a 2.5 fold increase.