Abstract

Lactic acid bacteria (LAB) are a group of Gram-positive; non-spore forming, non-motile, non-respiring, bacteria produces variety of antimicrobial compounds such as lactic acid, acetic acid, ethanol, formic acid, fatty acids, hydrogen peroxide and bacteriocins. Among them bacteriocines (a small molecular weight proteins) are in prime important due to their antimicrobial nature with food preservative abilities. Bacteriocins have gained a lot of attentions as bio-preservatives because of its GRAS status without causing any adverse effects on food. Nisin has been approved by US-FDA as a food preservative and is being used commercially worldwide by food industries. With these rationales, the aim of the present study is to produce bacteriocin (Nisin) from lactic acid bacteria isolated from selected fermented food sources, such as Curd, Mayonnaise and Jelly. Initially preserved lactic acid bacterial cultures were sub-cultured and their growth characters were studied on four different media namely MRS media, HJ media, KT media and DO media. Further seed culture of the selected bacterial species was prepared on the MRS broth (24hrs) and used as an inoculum for the production of bacteriocins. Later the 10% of the seed culture was inoculated to the 100 ml production media (CM media). After the 72 hrs of batch fermentation process, a crude extract of the fermentation broth was screened for the presence of Bacteriocins using agar well diffusion assay technique on E.coli and Kleibshella sp culture plates. All the three cultures of lactic acid bacteria showed antagonistic activity on the tested bacterial sp. Partial purification of the bacteriocin was done using ammonium sulphate precipitation and molecular weight characterisation of the obtained bacteriocins was done using Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis (SDS-PAGE). The results exhibited that, the bands representing the molecular weight less than 14 KDa and also the absorbance peak at 225 nm in UV spectra confirmed the presence of bacteriocin production. In conclusion in the present study attempt were made successfully in producing bacteriocine for indigenous cultures of LAB isolated from selected fermented foods samples.

Authors and Affiliations