Assessment of safety and probiotic properties of soil Bacillus spp. isolated from Mount Karadzica

Currently, while specific Bacillus species are utilized as probiotics, the exploration and integration of new, highly effective and safe probiotic strains remain a crucial concern within the fields of microbiology and the food industry. The focus on biodiversity within soil ecosystems has markedly intensified over the past two decades. Numerous studies have been conducted to isolate probiotic bacteria from various sources. This study aimed to isolate and evaluate the probiotic and safety potential of Bacillus spp. isolated from undisturbed soil. Forty-six spore-forming, Gram-positive Bacillus strains were isolated from four soil samples and assessed for in vitro probiotic potential. The tolerance to acidic pH, 0.3% bile salts, antimicrobial activity against foodborne pathogens, and antibiotic susceptibility was investigated, using physiological and biochemical tests. The preliminary antimicrobial screening showed that seven Bacillus spp. isolates inhibited the growth of Salmonella enterica ATCC 10708, with the highest activity exhibited by strain B30 (19.84 mm). The results revealed that the selected seven isolates were tolerant to 0.3% bile salts and survived incubation for 24 and 48 hours in nutrient broth at pH 3.00. An antibiotic susceptibility test of the isolates showed that the isolates are sensitive to the twenty-four tested antibiotics. Overall, this study has indicated the possibility of isolating potential probiotic bacteria from undisturbed soil and their application as candidates for enhancing the nutritional quality of diets and as safe additives in functional foods.