Isolation, molecular identification, and investigation of the probiotic potential of lactic acid bacteria isolated from Psidium guajava

Probiotics are non-pathogenic microorganisms that can interact with the stomach microbiota, and enhance their beneficial effects by improving the host immune system. These probiotics are generally isolated mostly from dairy and its byproducts. However, lactose-intolerant people and those who follow veganism are demanding probiotics from the non-dairy source hence for their purpose the present study focused on isolating lactic acid bacteria from Psidium guajava. The isolate was identified as Lactobacillus brevis using biochemical characterization and 16s RNA sequencing. Following this, a series of in vitro tests were conducted to determine the probiotic potential of the isolates including, survival in gut conditions (acid, bile, sodium chloride, phenol, gastric, pancreatin), lysozyme resistance, and survival at different temperatures. The isolate survived the harsh condition in the range of 77% to 99%. The safety assessment of the isolate was analyzed by an antibiotic susceptibility test in which the isolate was resistant to all 26 antibiotics, producing no hemolytic and Dnase activity. The antimicrobial activity against the pathogenic organism showed a good inhibitory effect. Considering the enzymatic potential of L.brevis, the presence of protease, lipase, and amylase enzymes were identified. The presence of exopolysaccharide and biofilm production was confirmed by the standard method. The adhesion ability was investigated and the cell surface hydrophobicity was 50.2%, autoaggregation was 92% and co- aggregation with E.coli was 55.2%. Cholesterol assimilating ability was confirmed by bile salt hydrosylate activity and percent assimilation was 55.4%. The result of these studies showed that L.brevis could be an excellent potential probiotic for application in the food and pharmaceutical industry.