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 Bacillus altitudinis 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 % (P < 0.01), 1.58 % (P < 0.05), and 10.68 % (P < 0.01), respectively, while crude protein content increased by 1.90 % (P < 0.01). Compared to the control group, supplementation with Bacillus altitudinis strain Z-99 enhanced the in vitro fermentation characteristics of wheat bran. In particular, it significantly increased the theoretical maximum gas production (P < 0.05) and elevated the content of acetic acid (P < 0.05), butyric acid (P < 0.05), isobutyric acid (P < 0.01), valeric acid (P < 0.05), and total short-chain fatty acids (P < 0.01). Furthermore, the addition of Bacillus altitudinis strain Z-99 significantly increased the abundance of Bifidobacterium (P < 0.05) and Blautia (P < 0.05), while decreasing the abundance of disease-associated Enterococcus (P < 0.01) and Actinobacillus (P < 0.05). Overall, a Bacillus altitudinis strain Z-99 with cellulose-degrading capacity was isolated from Tibetan pigs, and its functionality was validated through solid-state fermentation and in vitro fermentation methods. This study provided valuable insights into the utilization of wheat bran and the exploration of cellulose-degrading bacteria.