Characterization of a Cold-Active Xylanase from Paenibacillus sp. XP01, and Its Application in Hydrolyzing Alkali-Pretreated Corncob Residues

Xylan, a key hemicellulose in agricultural byproducts, is significantly underutilized in biorefineries. The human gut microbiome, with its diverse enzymes, holds great potential for biocatalyst discovery. In this study, <i>Paenibacillus</i> sp. XP01, a xylan-degrading strain, was isolated from human feces. Genomic analysis identified a GH11 <i>endo</i>-β-1,4-xylanase, designated Xyn157, which exhibited a cold-active property. It retained 47% residual activity at 0 °C and 72% at 4 °C. It also exhibited catalytic activity against insoluble xylan in corncob. Enzymatic profiling confirmed its endoacting mode, with xylotriose as the minimum substrate and branched chains impairing efficiency. Xyn157 hydrolyzed alkali-pretreated corncob residues (ACR) to produce xylo-oligosaccharide (XOS), with a yield of 6.4% (w/w). In vitro fermentation of Xyn157-treated ACR, which produced hydrolysis products of ACR (CRH), significantly promoted the growth of beneficial bacteria (e.g., <i>Bifidobacterium</i>, <i>Ligilactobacillus</i>), suppressed pathogens (e.g., <i>Enterobacter</i> and <i>Klebsiella</i>), and boosted short-chain fatty acid (SCFA) production compared to the ACR group. These findings highlight Xyn157's potential to convert insoluble xylan in ACR into functional prebiotics, expanding its applications in waste-to-prebiotic bioprocessing.