Abstract
The aim of the study was to isolate and characterize bacteriocin producing Lactic acid bacteria (LAB) from fermented foods prod- ucts and to exploit their potential as biopreservatives. The two Lactobacillus strains namely L. plantarum and L. fermentum exhibiting wide spectrum of activity against closely related strain were selected and screened for their bacteriocin producing ability. Cell free supernatant fluid collected from both the isolates and several gram positive and gram negative pathogens such as S.aureus, E.coli, P.aeruginosa, S.pneumoniae, Klebisella, and proteus were inhibited by the inhibitory action of bacteriocins in study. The bacteriocinogenic potential in these strains appeared non-inducible and increase in their titer was observed after exposure to different concentrations of UV light. The concentrat- ed crude bacteriocin samples subjected to ammonium sulphate precipitation resulted in an increased activity and high protein yield. By non- denaturing gel a band of approximately 8 KDa for L. fermentum and band corresponding to 37KDa in L. plantarum was seen. Physio-chemical characterization of the partially purified bacteriocin samples indicated heat (121°C for 60 min) and acidic pH stability (pH 2-6) of bacteriocin. Exposure to different carbon and other substations also resulted in increased bacteriocin titer. The high performance liquid chromatography was performed for L. plantarum.
Highlights
Lactic acid bacteria are a diverse group of genera which can be characterised as Gram-positive, catalase negative, non-sporulating, non-pigmented mesophils [1]
The present investigation highlights the isolation and characterization of bacteriocin producing Lactic acid bacteria (LAB) strains from fermented foods and were screened for bacteriocin production, from which four bacteriocinogenic strains were identified and selected for further study, representing four isolates of L. plantarum, L. fermentum, L. brevis and L. casei. This would indicate that a wide variety of bacteriocinproducing LAB are present on fermented milk, which represent an abundant resource of such potentially useful bacteria
Only few bacteriocin producing LAB has been reported in fermented foods [28]
Summary
Lactic acid bacteria are a diverse group of genera which can be characterised as Gram-positive, catalase negative, non-sporulating, non-pigmented mesophils [1]. The tolerated temperature range is generally between 5 and 50°C, with the optimum for most strains being about 30°C [2]. There is a lack of DNA homology between them. They lack the pathways for nitrate reduction, for the production of catalase and for the production of cytochromes and other pigments. They have a complex and variable nutritional requirement differing according to species [3]
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