Location: Bioproducts ResearchTitle: Breakdown of corn fiber by a metagenomic feruloyl esterase in combining actions with glycosyl hydrolases
Submitted to: Advances in Enzyme Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2021
Publication Date: N/A
Interpretive Summary: Corn fiber, a byproduct from wet-milling process of the corn-ethanol industry, is produced about 6.4 x 10^4 tons yearly, mostly used for animal feed. Corn fiber is highly recalcitrant due mostly to the hemicellulose fraction, which has a complex structure of heteroxylan. Numerous efforts have been directed to characterize the nature of its resistance to acid treatment and enzyme hydrolysis (as used in corn ethanol production). The recalcitrance can be ascribed to ferulic acid crosslinking of side units and/or backbone of the xylan structure, The present report describes enzymatic degradation of corn fiber using a metagenomic ferulic acid esterase in combining actions with glycosyl hydrolases individually or in in various combinations in a systematic approach with focus on sugar release.
Technical Abstract: A feruloyl esterase (FAE-C6) gene of 957 bp was isolated from rumen microbial metagenome, subcloned into pET32b vector, and expressed in Escherichia coli. The enzyme was purified in active form, consisted of 319 amino acid residues, with a molecular weight of 43.7 based on SDS-PAGE. Homology modeling showed that the FAE contained the catalytic triad composed of Ser154-Asp263His295 and a classical Gly-X-Ser154-X-Gly nucleophile motif commonly found in esterases. The FAE-C6 was characterized using corn fiber as substrate. Its combining actions with glycoside hydrolases (C, X, A) individually and in various combinations were studied with focus on the difference in effects on FA and sugar release. Glycoside hydrolases with endo-xylanase included in the enzyme mixture showed significant impact on increasing the FA yield. For the release of sugar, FAE enhanced the yield moderately in all hydrolases combinations and endo-xylanase was not a key factor in the enzyme formulation.