Inhibitory efficacy of nisin and bacteriocins from Lactobacillus isolates against food spoilage and pathogenic organisms in model and food systems

Antibacterial efficiency of bacteriocins from Lactobacillus isolates from appam batter (LABB), vegetable pickle (LABP) and nisin was evaluated individually and in combination against several Gram-positive and Gram-negative food spoilage and pathogenic organisms in liquid medium by pour plate method. When employed individually nisin was found to be a potent inhibitor of Clostridium sporogenes while the bacteriocins from Lactobacillus isolates, LABB and LABP were potent against Listeria monocytogenes and Staphylococcus aureus. LABB or LABP was better antibacterial in combination with nisin than when they were used alone. Gram-negative organisms were found to be resistant except for suppressing the growth of Escherichia coli by LABB or LABP and Pseudomonas by LABB or LABP or nisin only at the highest concentrations (320 AU/ml) until 24 h of incubation. However, the combination of LABB with nisin was more promising as there was no growth of Pseudomonas up to 72 h of incubation. The efficacy of these bacteriocins was also evaluated individually and in combination against L. monocytogenes and S. aureus in a vegetarian food model system. The bacteriocin LABB was found to be more effective as there was considerable inhibition of both L. monocytogenes and S. aureus as compared to either nisin or LABP while the combination of LABB with nisin proved to be more beneficial as there was maximum inhibition of both the organisms and no bloating of the sealed pouches was observed up to 14 days. It is concluded that bacteriocins in combination may be useful to improve the microbial quality and ultimately, the safety and shelf life of vegetarian foods.