A Novel Feruloyl Esterase-Producing Strain ZH-1 Belonging to Bacillus altitudinis from Baijiu Distiller’s Grains and Its Enzyme Cocktail with No Detectable β-Xylosidase Activity for Producing Functional Sugars from Arabinoxylan-Type Substrates

Arabinoxylan-rich agricultural residues are promising feedstocks for the production of high-value functional sugars and ferulic acid, yet their efficient enzymatic conversion is hindered by the complex crosslinked structures. This study aimed to isolate a novel feruloyl esterase-producing strain from Baijiu distiller’s grains and evaluate its enzyme cocktail for arabinoxylan degradation. A novel strain, Bacillus altitudinis ZH-1, was isolated and systematically characterized. Through one-factor-at-a-time optimization of both the medium and cultivation conditions, the feruloyl esterase activity was substantially increased (15.78-fold) compared with the activity obtained in the unoptimized Luria-Bertani (LB) medium. Genomic analysis revealed 103 unique carbohydrate-active enzyme (CAZyme)-encoding genes, including endoxylanases, α-L-arabinofuranosidases, and three putative feruloyl esterases. Studies on enzymatic properties revealed that the extracellular enzyme cocktail exhibited a hemicellulase-dominated profile and no detectable β-xylosidase activity under the assay conditions, with the three key enzymes showing over 76% of their maximum activity at pH 6.0 and 50 °C. In the degradation of insoluble wheat arabinoxylan, the enzyme cocktail released L-arabinose (69.00 mg/g substrate) and a xylooligosaccharides-equivalent fraction (244.00 mg/g substrate), which together accounted for 99.57% of total reducing sugars, along with ferulic acid (1.23 mg/g substrate). When applied to de-starched wheat bran, the enzyme cocktail achieved reducing sugar yields comparable to the commercial enzyme CTec2, while producing significantly higher levels of L-arabinose and xylooligosaccharides. These findings highlight the ZH-1 enzyme cocktail as an arabinoxylan-targeting biocatalyst with no detectable β-xylosidase activity under the assay conditions, showing promising potential for producing high-value functional sugars and ferulic acid from agricultural residues.