Abstract
Lactic acid bacteria (LAB), which are characterized by producing various functional metabolites, including antioxidants, organic acids, and antimicrobial compounds, are widely used in the food industry to improve gut health and prevent the growth of spoilage microorganisms. With the continual incidence of foodborne disease and advocacy of consumers for gut health, LAB have been designated as vital biopreservative agents in recent years. Therefore, LAB with excellent antimicrobial properties and environmental tolerance should be explored further. In this study, we focus on screening the LAB strains from a specialty pig (Bamei pig) feces of the Tibetan plateau region and determine their antimicrobial properties and environmental tolerance to evaluate their potential probiotic values. A total of 116 LAB strains were isolated, from which the LAB strain Qinghai (QP)28-1 was identified as Lactiplantibacillus (L.) plantarum subsp. plantarum using 16S rDNA sequencing and recA amplification, showing the best growth capacity, acid production capacities, environmental tolerance, hydrophobicity, antibiotic susceptibility, and bacteriocin production capacity. Furthermore, this strain inhibited the growth of multiple pathogens by producing organic acids and bacteriocin. These bacteriocin-encoding genes were identified using PCR amplification, including plnS, plnN, and plnW. In conclusion, bacteriocin-producing L. plantarum subsp. plantarum QP28-1 stands out among these 116 LAB strains, and was considered to be a promising strain used for LAB-related food fermentation. Moreover, this study provides a convenient, comprehensive, and shareable profile for screening of superior functional and bacteriocin-producing LAB strains, which can be used in the food industry.
Highlights
Probiotics are defined as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.” [1–3]
Bacteriocins, an antimicrobial substance produced by bacteria, are a class of antimicrobial proteins or peptides synthesized on ribosomes, which can be degraded by proteases, are safe for the organism, and do not induce resistance
16S rRNA gene sequence analysis with recA gene multiple detection, strains QP3-2, QP19-1, and QP28-1 were identified as L. plantarum subsp. plantarum, and QP4-2 and QP33-2 could be assigned to L. casei (Figure S2)
Summary
Probiotics are defined as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.” [1–3]. As one of the mainly important probiotics, lactic acid bacteria (LAB) have been widely adopted in the food fermentation industry to improve the flavor and taste of products, including cheese, beer, and yogurt. They can colonize the intestinal tract, promote the digestion and absorption of nutrients, and maintain the stability of the intestinal flora [4]. LAB have been shown to produce antimicrobial substances, including organic acids, hydrogen peroxide, reuterin, acetoin, diacetyl, antifungal peptides, and bacteriocin [5–8], and LAB with broad-spectrum antibacterial properties are widely used for inhibiting spoilage bacteria and foodborne pathogenic bacteria and prolonging food shelf lives [9]. There are still many difficulties to be solved and optimized in the process of screening probiotics and discovering bacteriocins, such as how to select more distinctive strains, how to screen target functional strains faster and more accurately, and how to discover bacteriocin-producing LAB efficiently
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