A cellulose-degrading Bacillus altitudinis from Tibetan pigs improved the in vitro fermentation characteristics of wheat bran

Wheat bran, a significant cereal by-product, is widely used in animal husbandry and the food industry. Our previous study identified a correlation between fiber utilization in Tibetan pigs and their efficient hindgut fermentation capacity. In this study, the <i>Bacillus altitudinis</i> strain Z-99, capable of cellulose degradation, was identified and isolated from Tibetan pigs. The results of solid-state fermentation demonstrated a significant reduction in neutral detergent fiber (NDF), acid detergent fiber (ADF), and hemicellulose content by 12.26 % (<i>P</i> < 0.01), 1.58 % (<i>P</i> < 0.05), and 10.68 % (<i>P</i> < 0.01), respectively, while crude protein content increased by 1.90 % (<i>P</i> < 0.01). Compared to the control group, supplementation with <i>Bacillus altitudinis</i> strain Z-99 enhanced the <i>in vitro</i> fermentation characteristics of wheat bran. In particular, it significantly increased the theoretical maximum gas production (<i>P</i> < 0.05) and elevated the content of acetic acid (<i>P</i> < 0.05), butyric acid (<i>P</i> < 0.05), isobutyric acid (<i>P</i> < 0.01), valeric acid (<i>P</i> < 0.05), and total short-chain fatty acids (<i>P</i> < 0.01). Furthermore, the addition of <i>Bacillus altitudinis</i> strain Z-99 significantly increased the abundance of <i>Bifidobacterium</i> (<i>P</i> < 0.05) and <i>Blautia</i> (<i>P</i> < 0.05), while decreasing the abundance of disease-associated <i>Enterococcus</i> (<i>P</i> < 0.01) and <i>Actinobacillus</i> (<i>P</i> < 0.05). Overall, a <i>Bacillus altitudinis</i> strain Z-99 with cellulose-degrading capacity was isolated from Tibetan pigs, and its functionality was validated through solid-state fermentation and <i>in vitro</i> fermentation methods. This study provided valuable insights into the utilization of wheat bran and the exploration of cellulose-degrading bacteria.