Probiotic characterization and spore production optimization of Lysinibacillus sp. MK212927.

Lysinibacillus sp. MK212927 exhibited strong antagonistic activity against multiple human enteropathogens.

• The strain was isolated from soil and selected based on its broad-spectrum antimicrobial activity.
• Antagonistic activity was demonstrated against multiple human enteropathogens.
• This activity was a primary criterion for selection for comprehensive probiotic characterization.

Lysinibacillus sp. MK212927 demonstrated high resilience under physiologically relevant stress conditions.

• The strain showed resilience to low pH, simulated gastric and intestinal fluids, bile salts, and thermal exposure.
• These conditions were chosen to simulate the gastrointestinal environment relevant to probiotic survival.
• The strain also displayed antioxidant capacity and bile salt hydrolase activity as additional desirable probiotic attributes.

Safety evaluation of Lysinibacillus sp. MK212927 revealed an absence of hemolytic activity and minimal cytotoxicity toward Caco-2 cells.

• The strain showed no hemolytic activity.
• Cytotoxicity toward Caco-2 intestinal cells was minimal.
• The strain was susceptible to vancomycin, levofloxacin, sulfamethoxazole, and doxycycline.
• Intermediate susceptibility was observed for azithromycin and amoxicillin, suggesting a lack of plasmids or mobile genetic elements.

Response surface methodology (RSM) optimization resulted in a 3.1-fold increase in biomass and a 5.4-fold increase in spore yield.

• Optimal conditions identified were pH 6.1, temperature 33.5°C, agitation at 200 rpm, and aeration at 0.21 vvm.
• Biomass production increased 3.1-fold under optimized conditions compared to baseline.
• Spore yield increased 5.4-fold under optimized conditions.
• RSM was applied specifically to enhance industrial applicability of the strain.

In vivo administration of Lysinibacillus sp. MK212927 improved body weight gain in rats.

• The in vivo assessment was conducted using a rat model.
• Administration of the strain resulted in improved body weight gain.
• This finding supports the strain's functional benefits as a feed supplement.
• The result was cited as supporting evidence for the strain's potential in animal and human nutrition.