Probiotic Potential and Antibiotic Resistance of Lactic Acid Bacteria Isolated from Curd in Sri Lanka
Lactic acid bacteria (LAB) are organisms beneficial to the human beings as probiotics which the organism can remain viable under stress conditions in the gastrointestinal tract.The aim of this study was to characterize and evaluate probiotic properties, and antibiotic resistance of thirteen isolates of lactic acid bacteria obtained from curd. In order to characterize the lactic acid bacteria isolates from curd; Gram’s staining, endospore staining, motility, catalase reaction, indole production, methyl red test, Voges-Proskauer test, citrate utilization, oxidase activity, urease activity, H2S production, arginine hydrolysis, growth at different temperatures, gas production from glucose and fermentation pattern of different carbohydrates were performed. In order to screen the probiotic potential of the isolates; tolerance to pH, bile, and phenol, survival in the presence of simulated gastric and pancreatic juices were examined. Antibiotic resistance of selected isolates was evaluated using 12 antibiotics. Results of biochemical tests and physiochemical tests revealed that all thirteen isolates (ITI_CD001, ITI_CD 002, ITI_CD 003, ITI_CD 004, ITI_CD 005,ITI_CD006, ITI_CD 009, ITI_CD 010, ITI_CD 011, ITI_CD 012 ITI_CD013, ITI_CD 014, andITI_CD 015) are belonged to the genus Lactobacillus. Species were identified as Lactobacillus plantarum, Lactobacillus brevis and Lactobacillus delbrukeii lactis. Most of the isolates were able to tolerate and grow well under low pH conditions (1.5 - 3.0), high pH (9.0), extremes of bile up to 0.5% and phenol up to 0.6%.The isolates were able to growin the presence of simulated gastric and pancreatic juices too. Results for the antibiotic resistance varied among isolates. Isolates ITI_CD004, ITI_CD 009, ITI_CD 010, ITI_CD 011, ITI_CD 012 and ITI_CD 015 were identified as higher probiotic isolates. The study revealed that the tested LAB isolates possess desirable probiotic properties. Hence, these isolates can be used to produce foods high in probiotics.
KEYWORDS: Curd, probiotics, Lactobacillus, antibiotic resistance