Biotechnological Approaches On The Fermentative Production Of Bacteriocin As Biopreservative

Lactic acid bacteria (LAB) are historically known as the milk-souring bacteria, which are often associated with various food fermentation processes. LAB produce a variety of metabolites such as H2O2, diacetyl group, organic acids and bacteriocins which act as preservation factors in food fermentation. Among these metabolites, bacteriocins have gained economic importance due to their broad spectrum of activity, resistance to temperature, activity in a wide pH range, low molecular weight proteins and the fact that their production can be engineered through the means of rDNA technology. Recently, these antimicrobial proteins/peptides have received world-wide attention due to their ability to preserve food and as possible substitute for chemical preservatives that are recognized as carcinogenic and mutagenic. Nisin is broad spectrum class I bacteriocin, commercially exploited to increase the shelf-life of food commodities by preventing spoilage by Clostridium botulinum and has gained importance in the preservation of canned foods and dairy products. However, several studies have shown that there are other LAB bacteriocins with great potential for use in food preservation, with broad-spectrum of antimicrobial activity across a wide pH range: particularly the class IIa bacteriocins. Recently, a commercial preparation of pediocin PA-1 known as fermentate AltaTM 2341 was formulated. This formulation is known to extend shelf-life of a variety of foods, particularly by inhibiting the growth of Listeria monocytogenes in ready-to eat-meat products. This indicates that pediocin-type of bacteriocins are next in line after successful use of nisin for preservation of food. Various natural sources and food fermentation processes have been exploited for the isolation of bacteriocinogenic strains of LAB. Likewise, pediocin producers have been reported from meat and vegetable sources. Bacteriocinogenic LAB from intestinal sources have the dual advantage that they posses both antimicrobial properties and those of probiotics. Bacteriocin producing LAB are generally isolated and identified using conventional microbiological tools. However, combining tools for their routine identification with those molecular biology and biochemical methods will provide detailed information about the genetic make-up of a particular strain of an industrially important microorganism. The use of DNA probes, PCR, plasmid profiling and antibiogram have been suggested as tools to achieve this goal.Recently, it has been shown that pediocin PA-1 production is not only confined within strains of Pediococcus acidilactici but is also found among strains of Lactobacillus plantarum, Pediococcus parvulus and Bacillus coagulans. This indicates that there is a need to study pediocin producers isolated from different environments and to characterize them in detail by using the various technique of molecular biology. rRNA typing and nucleotide sequencing of the genes involved in cellular functions are important tools in the identification and fingerprinting the target organisms. Very few bacteriocins have been produced in food-grade media. Food-grade medium such as whey permeate offers the advantages of not only being inexpensive but also of allowing direct utilization/consumption of the product as a bacteriocin-rich-dairy ingredient. In the present study, emphasis has been laid on the production of pediocin in a whey permeate medium. There have been only few reports on the heterologous expression of bacteriocin genes in E. coli. Expression of pediocin as a fusion protein allows high level expression and purification in a single step. Hyper-expression of the immunity protein offers scope for study of its function and its interaction with pediocin.