Two Antimicrobial Peptides Derived from Bacillus and Their Properties

Growth promotion and disease prevention are important strategies in the modern husbandry industry, and for this reason, antibiotics are widely used as animal feed additives. However, the overuse of antibiotics has led to the serious problem of increasing resistance of pathogenic microorganisms, posing a major threat to the environment and human health. "Limiting antibiotics" and "Banning antibiotics" have become the inevitable trends in the development of the livestock feed industry, so the search for alternative antimicrobial agents has become a top priority. Antimicrobial peptides (AMPs) produced by Bacillus spp. have emerged as a promising alternative to antibiotics, due to their broad-spectrum antimicrobial activity against resistant pathogens. In this study, two strains of Bacillus velezensis 9-1 and B. inaquosorum 76-1 with good antibacterial activity were isolated from commercial feed additives, and the antimicrobial peptides produced by them were purified by ammonium sulfate precipitation, anion exchange chromatography, gel chromatography, and RP-HPLC. Finally, two small molecule peptides, named peptide-I and peptide-II, were obtained from strain 9-1 and 76-1, respectively. The molecular weight and sequences of the peptides were analyzed and identified by LC-MS/MS, which were 988.5706 Da and VFLENVLR, and 1286.6255 Da and FSGSGSGTAFTLR, respectively. The results of an antibacterial activity and stability study showed that the two peptides had good antibacterial activity against Staphylococcus aureus, B. cereus, and Salmonella enterica, and the minimum inhibitory concentrations were 64 μg/mL and 16 μg/mL, 32 μg/mL and 64 μg/mL, and 8 μg/mL and 8 μg/mL, respectively. All of them have good heat, acid, and alkali resistance and protease stability, and can be further developed as feed antibiotic substitutes.