Two putatively novel bacteriocins active against Gram-negative food borne pathogens produced by Weissella hellenica BCC 7293

Abstract

Weissella hellenica BCC 7239, isolated from Thai fermented pork sausage called Nham, produced two putatively novel bacteriocins, 7293A and 7293B. Both bacteriocins had broad antimicrobial spectra and exceptionally inhibited several important Gram-negative food-borne pathogens (Pseudomonas aeruginosa, Aeromonas hydrophila, Salmonella Typhimurium and Escherichia coli). The highest amount of bacteriocin was produced in MRS and APT media at 30 °C without agitation. Bacteriocin 7293A showed relatively higher antimicrobial activity than bacteriocin 7293B. However, pH and thermal stability of bacteriocin 7293A was lower. These bacteriocins were of proteinaceous nature, in which the complete inactivation of their antimicrobial activity after treatment by proteolytic enzymes, including trypsin, α-chymotrypsin, pepsin and protease K was observed, whilst lipase and α-amylase exhibited no effect. Antimicrobial activity of both peptides was also not inactivated by organic solvents (ethanol, isopropanol, acetone, acetonitrile) and surfactants (Tween 20, Tween 80 and Triton X-100). Bacteriocin 7293A and B exhibited bactericidal effect against both Gram-positive and Gram-negative indicators without cell-lysis. According to ESI/MS analysis, the molecular masses of bacteriocin 7293A and B were determined to be 6249.302 and 6489.716 Da, respectively. Because their molecular masses were not similar to those of other known bacteriocins, both bacteriocin 7293A and B could be novel bacteriocins. Thus, both novel bacteriocins hold promise for applications in the prevention or treatment of pathogenic infections as food and feed additives to replace antibiotics for enhancing the productivity and sustainability of food animals.