Detection, partial purification and characterization of bacteriocin produced by Lactobacillus brevis FPTLB3 isolated from freshwater fish: Bacteriocin from Lb. brevis FPTLB3

Abstract

Lactobacillus brevis FPTLB3 was isolated from freshwater fish, capable of producing bacteriocin that had broad spectrum of inhibition (3200 AU/ml) against Escherichia coli MTCC 1563, Enterococcus faecalis MTCC 2729, Lactobacillus casei MTCC 1423, Lactobacillus sakei ATCC 15521 and Staphylococcus aureus ATCC 25923. The antimicrobial activity of crude supernatant fluid was stable after heating at 121 °C for 60 min and declined thereafter. Stability of antimicrobial activity was observed at pH range of 2.0 to 8.0. Its active principle was proteinaceous in nature since the bacteriocin was inactivated by proteolytic enzymes, but not by other non-proteolytic enzymes. Mitomycin C and UV light did not affect the activity of the bacteriocin, while chloroform extraction completely destroyed their activity. Exposure to surfactant resulted in an increase in titre, except Nonidet P-40, which led to total loss of activity. No bacteriocin adsorption was detected at pH 1 to 2, whereas 100% bacteriocin adsorption was found at pH 6.5. Based on Tricine SDS-PAGE the estimated molecular mass of bacteriocin was 54 kDa. No plasmid was found to present in the isolate.

Keywords: Antimicrobial activity; Bacteriocin; Biopreservation; Lactic acid bacteria; Lactobacillus brevis.

Fig. 1

Tricine SDS-PAGE of bacteriocin produced by Lactobacillus brevis FPTLB3. Coomassie brilliant blue R-250 stained gel, Lane 1: molecular mass markers and Lane 2: bacteriocin

Fig. 2

a Bacteriocin production (AU/ml)^a by Lactobacillus brevis FPTLB3 with time. b The increasing optical density (OD₆₀₀) value^a of Lactobacillus brevis FPTLB3, showing decreasing pH value^a with time. ^aResults are mean of three determination (n = 3) with S.D

Fig. 3

Effect of CSF produced^a by Lactobacillus brevis FPTLB3 on indicator organism. ^aResults are mean of three determination (n = 3) with S.D

Fig. 4

Effect of time and temperature on activity^a of CSF. ^aResults are mean of three determination (n = 3) with S.D

Fig. 5

Effect of storage time and temperature on antimicrobial activity^a of CSF. ^aResults are mean of three determination (n = 3) with S.D