Xylooligosaccharide recovery from sugarcane bagasse using β-xylosidase-less xylanase, BsXln1, produced by Bacillus stercoris DWS1: Characterization, antioxidant potential and influence on probiotics growth under anaerobic conditions.

Xylooligosaccharides (XOS) are excellent prebiotic which improve health through selective modulation of beneficial gut microbiome. Its production from agroresidues using microbial xylanase is considered as sustainable and economic approach. In this study a xylanase producing bacterium isolated from decaying wood soil was phylogenetically identified and designated as Bacillus stercoris DWS1. Xylanase (BsXln1) purified from the bacterium had pH and temperature optima of 7 and 37-60 °C, respectively, and it retained 85 % activity upon preincubation at 60 °C for 40 min. Indicating its moderate thermostability. Zymogram analysis of partially purified BsXln1 revealed its molecular weight of ∼35 kDa. B. stercoris DWS1 produced 200 U mL of BsXln1 in presence of 1.5 % sugarcane bagasse (SCB) as carbon source; which was enhanced to 591 U mL through optimization of cultural conditions. Xylan extracted from SCB was morphologically and structurally characterized, and then depolymerized by BsXln1 to yield XOS (400 mg g). Analysis of purified XOS by TLC, followed by ESI-MS showed predominance of xylobiose and xylotriose. XOS exhibited in vitro antioxidant activities against DPPH and ABTS free radicals, however, it had limited prebiotic activity on Lactobacillus plantarum and Lactobacillus fermentum under anaerobic condition. In conclusion, the xylanase, BsXln1, produced by B. stercoris DWS1 can be used in food industries for efficient production of bioactive XOS from agroresidues.