Abstract
Yaks (Bos grunniens) live primarily in high-altitude hypoxic conditions and have a unique intestinal micro-ecosystem, remarkable adaptability, and strong climatic resistance. Accumulating evidence revealed the importance of probiotics in host metabolism, gut microbiota, growth performance, and health. The goal of this study was to screen out probiotics with excellent probiotic potential for clinical application. In this study, four strains of Bacillus, i.e., Bacillus proteolyticus (named Z1 and Z2), Bacillus amyloliquefaciens (named J), and Bacillus subtilis (named K), were isolated and identified. Afterward, their probiotic potential was evaluated. Antioxidant activity tests revealed that Z1 had the highest DPPH and hydroxyl radical scavenging activity, whereas Z2 had higher reducing power and inhibited lipid peroxidation. Additionally, the antibacterial testing revealed that all strains were antagonistic to three indicator pathogens, Escherichia coli C83902, Staphylococcus aureus BNCC186335, and Salmonella enteritidis NTNC13349. These isolates also had a higher hydrophobicity, autoaggregation, and acid and bile tolerance, all of which helped to survive and keep dangerous bacteria out of the host intestine. Importantly, all strains could be considered safe in terms of antibiotic susceptibility and lack of hemolysis. In conclusion, this is the first study to show that B. proteolyticus and B. amyloliquefaciens isolated from yaks have probiotic potential, providing a better foundation for future clinical use.
Highlights
Reactive oxygen species (ROS) is a single-electron reduction product of oxygen in the body, including superoxide anion, hydroxyl radical, and hydrogen peroxide (Mukherjee et al, 2014)
Oxidative stress is a series of damage processes of lipid peroxidation, protein denaturation, and DNA hydroxylation, all of which are primarily produced by oxygen free radicals when the body is unable to remove them
Our results firstly revealed that Z1 and Z2 (B. proteolyticus), J (B. amyloliquefaciens), and K (B. subtilis) isolated from yaks have good free radical scavenging ability and probiotic properties
Summary
Reactive oxygen species (ROS) is a single-electron reduction product of oxygen in the body, including superoxide anion, hydroxyl radical, and hydrogen peroxide (Mukherjee et al, 2014). Oxidative stress is a series of damage processes of lipid peroxidation, protein denaturation, and DNA hydroxylation, all of which are primarily produced by oxygen free radicals when the body is unable to remove them. Oxidative stress can reduce production performance and meat quality, resulting in severe economic losses to the breeding industry, some synthetic antioxidants such as butylated hydroxytoluene and tert-butylated hydroxyanisole are widely used to relieve oxidative stress (Hossain et al, 2020). These antioxidants are not currently recommended due to hepatic injury and carcinogenicity. Increasing research is devoted to finding safer and more natural antioxidants to alleviate the adverse effects of oxidative damage
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