ABSTRACT
Introduction: Curd is a potential source of probiotic Lactobacillus species. Methods: This study was carried out to isolate and characterise Lactobacillus species available in curd samples sold in the market. Nine curd samples prepared using cow or buffalo milk were obtained from a local market in the Kandy district. Results: Seven isolates (LB 1-7) were identified based on their colony morphology and biochemical characteristics and evaluated for probiotic attributes such as low pH tolerance, resistance to bile salts, antimicrobial activity against Escherichia coli and Pseudomonas aeruginosa, antibiotic activity against erythromycin, chloramphenicol and norfloxacin, haemolytic activity and DNase activity. All isolates were able to grow at low pH (pH=3.0) and were able to survive at 0.3% bile salt, however, the viability decreased with time. LB7 showed very low viability with bile salt compared to others. All isolates exhibited antimicrobial activity against the two pathogenic organisms tested. Two isolates (LB1 and LB2) showed maximum zone of inhibition (18±1.13mm) against E.coli and four isolates (LB1, LB2, LB6 and LB7) against P.aeruginosa. Only LB6 and LB7 exhibited resistance to all three antibiotics tested while the other isolates were sensitive. In general, a higher sensitivity was shown against erythromycin and chloramphenicol compared to norfloxacin. All isolates exhibited δ-haemolysis (non-haemolysis) while none of the isolates showed any DNase activity. Conclusions: Tested isolates showed probiotic attributes such as resistance to low pH, tolerance to bile salt, antimicrobial resistance, antibiotic activity, non-haemolysis and no DNase activity.
