ISOLATION AND CHARACTERIZATION OF BACTERIOCINOGENIC LACTIC ACID BACTERIA FROM INDIGINOUS DAIRY SOURCE AND ITS ANTIMICROBIAL POTENTIAL

The aim of this research was to isolate lactic acid bacterial (LAB) strains, characterize them and classify the bacteriocin producing LAB strain from indigenous dairy sources. Antimicrobial potential of LAB strain was tested against L. monocytogens. The antimicrobial compound was also tested for maintaining the decreased colony forming unit (CFU) for minimally processed vegetables like carrots, cabbage and lettuce in second phase of the research. The initial identification was based on conventional morphological and biochemical analysis while the final confirmation was done by utilizing advanced molecular tools. Prior to all these manipulations the growth conditions were carefully optimized for the respective strains. The study finally led us to conclude that Lactococcus lactis subsp. lactis was the most abundant type of lactic acid bacteria found in indigenous dairy products (sour cream and cheese) samples studied. A bacteriocin (Lacticin SC07) produced during the growth of Lactococcus lactis subsp. lactis was purified partially by using biochemical technique ammonium sulfate precipitation in different percentages (60% and 80%). These precipitations lead to a 437-fold increase in total lacticin SC07 activity. SD S-PAGE electrophoretic pattern of lacticin showed that it is a single peptide band of 1.7 kDa. But, 3.7 kDa dimers also showing lacticin SC07 activity. The findings of my research revealed that the isolated LAB strain has good potential for bacteriocin production and antimicrobial potential that exerts in the usage of this bacteriocin (lacticinSC07) as a natural preservative in minimally processed vegetable industry.