Antimicrobial compounds produced by Lactobacillus sakei subsp. sakei 2a, a bacteriocinogenic strain isolated from a Brazilian meat product

Abstract

Bacteriocins produced by lactic acid bacteria are gaining increased important due to their activity against undesirable microrganisms in foods. In this study, a concentrated acid extract of a culture of Lactobacillus sakei subsp. sakei 2a, a bacteriocinogenic strain isolated from Brazilian pork product, was purified by cation exchange and reversed phase chromatografic methods.The amino acid sequences of the actives antimicrobial compounds determinated by Edman degradation were compared to known protein sequences using the BLAST-P software. Three different antimicrobial compounds were obtained P1, P2 and P3, and mass spectrometry indicated molecular masses of 4.4, 6.8 and 9.5 kDa, respectively. P1 corresponds to classical sakacin P, P2 is identical to the 30S ribosomal protein S21 of L. sakei subsp. sakei 23K and P3 is identical to a histone-like DNA-binding protein HV produced by L. sakei subsp. sakei 23K.Total genomic DNA was extracted and used as target DNA for PCR amplification of the genes sak, lis and his involved in the synthesis of P1, P2 and P3. The fragments were cloned in pET28b expression vector and the resulting plasmids transformed in E. coli KRX competent cells. The transformants were active against L. monocytogenes, indicating that the activity of the classical sakacin P produced by L. sakei 2a can be complemented by other antimicrobial proteins.