Bacteriocin production by lactic acid bacteria encapsulated in calcium alginate beads

Abstract

Thirty two strains of lactic acid bacteria were isolated form traditional fermented foods and bio-extract for their abilities to produce bacteriocins. One strain, LAB7, which isolated from bio-extract were found to be able to inhibit Escherichia coli TISTR 780 and Staphylococcus aureus TISTR 1466. Its properties were heat tolerance at 121 °C for 15 min and stable at wide pH range of 2-9. The encapsulation experiments were conducted with LAB7 strain entrapped in calcium alginate beads which contained 106 CFU/bead. The encapsulated cells were inoculated into MRS broth at 10% inoculums and grew in batch condition at 30°C for 24 h. Free cells with and without agitation were used to compare the effect of encapsulation on the bacteriocin production. Substrate consumption, biomass and lactic acid production were also investigated. The results showed that the encapsulated cells produced the highest lactic acid at 2.92 g/l/h. The bacteriocin activity against E. coli TISTR 780 was 3200 AU/ml after cultured for 10 h and the activity against S. aureus TISTR 1466 was 800 AU/ml after cultured for 8 h. Whereas, free cells without agitation condition gave bacteriocin activity against E. coli TISTR 780 and S. aureus TISTR 1466 only 1600 AU/ml and 400 AU/ml, respectively. It was indicated that LAB7 not only produced bacteriocin against both Gram positive and Gram negative bacteria, but also strongly present high bacteriocin activity when encapsulated cell in calcium alginate beads.