Abstract
Bacillus thuringiensis (Bt), one of the most successful biopesticides, may expand its potential by producing bacteriocins (thuricins). The aim of this study was to investigate the antimicrobial potential of a novel Bt bacteriocin, thuricin BtCspB, produced by Bt BRC-ZYR2. The results showed that this bacteriocin has a high similarity with cold-shock protein B (CspB). BtCspB lost its activity after proteinase K treatment; however it was active at 60 °C for 30 min and was stable in the pH range 5–7. The partial loss of activity after the treatments of lipase II and catalase were likely due to the change in BtCspB structure and the partial degradation of BtCspB, respectively. The loss of activity at high temperatures and the activity variation at different pHs were not due to degradation or large conformational change. BtCspB did not inhibit four probiotics. It was only active against B. cereus strains 0938 and ATCC 10987 with MIC values of 3.125 μg/mL and 0.781 μg/mL, and MBC values of 12.5 μg/mL and 6.25 μg/mL, respectively. Taken together, these results provide new insights into a novel cold shock protein-like bacteriocin, BtCspB, which displayed promise for its use in food preservation and treatment of B. cereus-associated diseases.
Highlights
The increasing trend of limiting the use of chemical food preservatives has stimulated research in the field of biopreservation to find an attractive and alternative approach to chemical preservatives
The screening of bacteriocin producers from 79 Bacillus thuringiensis (Bt) strains led to the identification of six Bt strains active against B. cereus 0938 and 19 Bt strains toxic to B. cereus ATCC 10987
To demonstrate that the increase in antibacterial activity was due to an increase in the amount of bacteriocin produced by the strain and that the strain produced the same peptide at 34 h, the bacteriocin-like inhibitory substances (BLIS) samples were further analyzed using a tricine sodium dodecylsulfate (SDS) polyacrylamide gel
Summary
The increasing trend of limiting the use of chemical food preservatives has stimulated research in the field of biopreservation to find an attractive and alternative approach to chemical preservatives. Bacteriocins are receiving attention due to their Generally Recognized as Safe (GRAS) status[1]. Bacteriocins that are synthesized by lactic-acid-producing bacteria have been well studied. Only commercially produced bacteriocins are Nisin (Lactococcus lactis) and Pediocin (Pediococcus acidilactici). A considerable number of Bt BLIS have been reported in the literature, but only three Bt bacteriocins (thuricin-17, thurincin H and thuricin CD) with known amino acids have been thoroughly characterized[5,14]. Many bacteriocins remain to be explored for their potential in food preservation and applications in agriculture as well as human and animal health. A novel bacteriocin that is active against B. cereus and produced by Bt BRC-ZYR2 isolated from uranium-contaminated soil[7] was purified and characterized, and its antibacterial efficacy was evaluated
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