Abstract
Soy whey is a by-product from the processing of soybean products, which is generally discarded and considered as waste. In recent years, a large number of bacteriocins produced by bacteria have been described. However, the production of bacteriocins in soy whey has not yet reported. Bacteriocin-like substance producing B. spp JY-1 was isolated from Chinese traditional fermented soybean (douchi) in previous study. In present study, the antimicrobial spectrum, and the effect of enzymes, pH and heat on the antibacterial activity of bacteriocin-like substance produced by B. spp JY-1 were evaluated. Then, the effects of supplement of carbon and nitrogen sources on the production of bacteriocin-like substances in soy whey were also investigated. Results obtained indicated that bacteriocin-like substance in cell-free supernatant of JY-1 exhibited broad inhibitory spectrum both against some food-borne pathogens. The bacteriocin-like substance JY-1 was sensitive to trypsin and pepsin, but stable between pH 2.0-10, and heat resistance (65-105°C). In addition, the production of bacteriocin-like substance JY-1 started at the early exphonential phase and reached its maximum at the stationary phase. The antimicrobial activity of cell-free supernatant of JY-1 cultured in soy whey was observed. The supplement of soluble starch or beef extract in soy whey yielded a higher production of bacteriocin-like substance. The results indicated that the bacteriocin-like substance JY-1 may be a potential candidate for alternative agent to control important food pathogens, and the soy whey has potential for production of bacteriocins.
Highlights
Bacteriocins are ribosomally synthesized antibacterial peptides that posses antagonistic activity toward closely related strains, while its producer cells are immune to their own bacteriocins [1]
In the study conducted by Lim [4] revealed that Bacillus amyloliquefaciens J4 isolated from Korean traditional fermented soybean paste had a broad spectrum of antibacterial activity against various food-borne pathogens, especially the Listeria monocytogenes, the antimicrobial activity of bacteriocin J4 was completely abolished by treatment with proteolytic enzymes
In order to study the antimicrobial spectrum of bacteriocin-like substances of JY-1, several lactic acid bacteria (LAB) strains and food-borne pathogenic bacteria comprising both Gram-positive and Gram-negative members were tested (Table 1)
Summary
Bacteriocins are ribosomally synthesized antibacterial peptides that posses antagonistic activity toward closely related strains, while its producer cells are immune to their own bacteriocins [1]. Bacillus strains are generally known to be thermo-tolerant and spore-forming species that show rapid growth in liquid culture and are widely distributed in environment, such as soil, fermented foods. There is growing interest in recent research on the isolation and identification of the bacteriocin-producing Bacillus spp. from the fermented foods. In the study conducted by Lim [4] revealed that Bacillus amyloliquefaciens J4 isolated from Korean traditional fermented soybean paste had a broad spectrum of antibacterial activity against various food-borne pathogens, especially the Listeria monocytogenes, the antimicrobial activity of bacteriocin J4 was completely abolished by treatment with proteolytic enzymes. Previous study reported that B. amyloliquefaciens EMD17 isolated from Cheonggukjang strongly inhibited growth of L. monocytogenes, Bacillus cereus, and the antimicrobial
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