Harnessing the power of Bacillus subtilis MR42: direct production of defined xylooligosaccharides (XOS) from corn stalks with enhanced prebiotic properties.

The production of value-added bioproducts from renewable carbon sources has gained increasing attention in recent years. The aim of this study was to develop economical approaches for the production of prebiotic XOS with defined degree of polymerization (DP) by Bacillus subtilis MR42 from corn stalks. The MR42 strain has been genetically modified to delete the xynC gene, which enables it to convert xylan into specific XOS without generating xylose as a byproduct. Under optimal conditions, a high yield of XOS (703.4 mg/g xylan) was obtained. The purified XOS were further characterized using various techniques including TLC, HPLC, ESI-MS and ¹HNMR spectroscopy. The analysis revealed that the XOS primarily consisted of xylotriose (257 ± 0.14 mg/g XOS), xylotetraose (267 ± 0.24 mg/g XOS) and xylopentaose (289 ± 0.29 mg/g XOS), accounting for 81.3% of the total XOS. The prebiotic effect of XOS was evaluated by examining its impact on the growth of Lactobacillus, the production of short-chain fatty acids, and its antioxidant activity. B. subtilis MR42 showed a promising ability to produce XOS of DP 3-5, without the generation of xylose.