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An attempt was made, to characterize natural antibiotics or lantibiotics from unconventional sources and its antibacterial spectrum against food borne pathogens and drug resistant bacteria. Six different traditional fermented foods i.e., fermented fish, fermented soybeans, Soibum (fermented bamboo shoots), milk, idly and dosa batter were used for the isolation of bacteriocin producing Lactic acid bacteria (LAB). Among all bacterial cultures isolated from the various sources, 129 cultures have found to produce antimicrobial compounds. Nisin specific reporter bacteria was utilized as biosensor to identify the Nisin like bacteriocin, where 10 cultures found to be positive Nisin producer. Identified Nisin like bacteriocin was partially concentrated by using ammonium sulphate followed by butanol extraction. Minimum inhibitory concentration (MIC) was analyzed against food borne pathogen and drug resistant bacteria. MIC of partially purified Nisin (pp-Nisin) of all the LAB isolates against food-borne pathogens are ranged between 0.5 and 92 µg/ml respected to various Gram-positive bacteria. Similarly, the drug resistant bacteria were also inhibited by pp-Nisin (MIC ranged between 15 and 175 µg/ml). All samples of ppnisin exhibited auto induction ability. Taxonomic identification of the nisin producers was done by whole genome sequencing which reveals that cultures belongs to Lactococcus lactis ssp. lactis. Also it was found that Lactococcus lactis ssp. lactis C2d and Lactococcus lactis ssp. lactis SP2C4 harbor nisA gene and Lactococcus lactis ssp. lactis FS2 (L. lactis FS2) harbor nisQ gene. The finding of this study highlights the first case of L. lactis FS2 isolated from fermented fish harbor nisQ gene. Antibacterial activity of pp-Nisin against drug resistant LAB is also reported.

Worldwide demand for safe, environment-friendly preservatives that prevent food spoilage by using antimicrobial compound produced by food-grade microorganisms as a preservative continue to increase. Some chemical preservatives cause harmful effects, such as a headache, allergies, asthma, and skin diseases. Lactic acid bacteria (LAB) and metabolites derived from it are being considered as a source of biopreservative due to their lack of adverse effect on human health and GRAS (Generally recognized as safe) by the American Food and Drug Administration (FDA). Some LABs produce bactericidal proteins known as bacteriocins, which target specific bacteria. Bacteriocins act by forming pores in the targeted bacteria and by synergistically impacting elevated thermal stress and pH activity over a vast range of applications. Bacteriogenic cultures can also act as a starter culture or cocultures in combination with a defined starter culture for fermented products. Nisin is a bacteriocin produced by Lactococcus lactis and has antimicrobial activity against gram-positive bacteria. Ten variants of nisin are found to date that includes recently identified, nisin O. They vary from each other by one to 10 amino acid differences and are available in the market with the name of Nisaplin (2.5% nisin A). Nowadays, nisin is used by food manufacturers as a food preservative to inhibit the growth of foodborne gram-positive pathogens (e.g., Listeria monocytogenes). Nisin is a thermal stable protein that can serve in antimicrobial packaging. Other bacteriocins, such as subtilin, enterocin, etc., can also be used in antimicrobial packaging and other food preservation applications are expected to escalate in the forth-coming years. This chapter describes the industrial perspective of food preservatives from a microbial origin that has been shown promising results in extending the shelf-life of food commodities.