Lactiplantibacillus plantarum BX62 reduces methane production, and improves antioxidant capacity and rumen fermentation in vitro

Abstract

This study was conducted to evaluate the effects of Lactiplantibacillus plantarum BX62 with high-antioxidant activity on the dynamics of antioxidant capacity, rumen fermentation, methane (CH4) emission, and ruminal bacterial diversity during incubation of alfalfa substrate by in vitro fermentation. The rumen inocula from sheep were incubated in batch cultures in three groups: (1) control group without inoculation, (2) L. plantarum MTD/1 (MTD) inoculated-group, and (3) L. plantarum BX62 (BX) inoculated-group. The incubations were maintained for 3, 6, 12, 24 and 36 h, with 3 replicates per group and incubation time point. Results showed that the groups × incubation time interactions (P < 0.05) were significant for gas production (GP), CH4 production, and dry matter digestibility (DMD). The BX-inoculated group increased GP (P < 0.05) and DMD (P = 0.001) at 3 h and 6 h of fermentation versus control, whereas decreased the CH4 production (P < 0.05) at 24 h and 36 h of fermentation. In addition, compared to control, two inoculation groups increased total volatile fatty acid (P = 0.028) and acetate (P = 0.034) concentrations at 3 h of fermentation. Total antioxidant capacity during fermentation, except after 6 h, was higher (P < 0.001) for both inoculated groups than control. Higher (P < 0.05) superoxide dismutase activity during fermentation was also found with both inoculated groups than control. BX- and MTD-inoculated groups notably decreased NAD+ content (P < 0.05) and NAD+ to NADH ratio (P < 0.05) versus control at 3 h and 6 h of fermentation. Bacteroidetes abundance increased (P < 0.05) while Firmicutes decreased (P < 0.05) for both inoculated groups compared to control. The relative abundances of fibrolytic bacteria such as Prevotella_1 and Lachnospiraceae, and of H2-incorporating bacteria, such as Succinivibrio, were higher (P < 0.05) for BX- and MTD-inoculated groups than control. In conclusion, the BX strain with high-antioxidant activity could be used as a candidate strain to improve the in vitro antioxidant status of ruminants and might have the potential to mitigate CH4 emissions by competing for hydrogen utilization with methanogens, but it had little difference with the MTD strain.