Abstract
In this study, five bacteriocin-producing Lactococcus lactis strains were identified from different naturally fermented Brazilian sausages. Ion exchange and reversed-phase chromatographies were used to purify the bacteriocins from culture supernatant of the five strains. Mass spectrometry (MALDI-TOF/TOF) showed that the molecular masses of the bactericoins from L. lactis ID1.5, ID3.1, ID8.5, PD4.7, and PR3.1 were 3330.567 Da, 3330.514 Da, 3329.985 Da, 3329.561 Da, and 3329.591 Da, respectively. PCR product sequence analysis confirmed that the structural genes of bacteriocins produced by the five isolates are identical to the lantibiotic nisin Z. Optimal nisin Z production was achieved in tryptone and casein peptone, at pH 6.0 or 6.5. The most favorable temperatures for nisin Z production were 25°C and 30°C, and its production was better under aerobic than anaerobic condition. The type of carbon source appeared to be an important factor for nisin Z production. While sucrose was found to be the most efficient carbon source for nisin Z production by four L. lactis isolates, fructose was the best for one isolate. Lactose was also a good energy source for nisin Z production. Surprisingly, glucose was clearly the poorest carbon source for nisin Z production. The five isolates produced different amounts of the bacteriocin, L. lactis ID1.5 and ID8.5 isolates being the best nisin Z producers. DNA sequence analysis did not reveal any sequence differences in the nisZ and nisF promoter regions that could explain the differences in nisin Z production, suggesting that there should be other factors responsible for differential nisin Z production by the isolates.
Highlights
Lactic acid bacteria (LAB) constitute a diverse group of bacteria that produce lactic acid as a major end-product of hexose fermentation. ey are widely used as starter cultures in the production of many fermented foods [1]
We report the identification and production of bacteriocins produced by LAB isolated from sausage (Italian type)
In order to purify the bacteriocins produced and secreted by five L. lactis strains, three steps of purification were carried out from the cell free supernatant. e highest active fraction of the bacteriocin was eluted with 30% to 40% isopropanol for all strains. e molecular masses of the purified fractions from L. lactis ID1.5, ID3.1, ID8.5, PD4.7, and PR3.1 were 3330.567 Da, 3330.514 Da, 3329.985 Da, 3329.561 Da, and 3329.591 Da, respectively (Figure 1), which are similar to the molecular mass of the nisin Z
Summary
Lactic acid bacteria (LAB) constitute a diverse group of bacteria that produce lactic acid as a major end-product of hexose fermentation. ey are widely used as starter cultures in the production of many fermented foods [1]. Ey are widely used as starter cultures in the production of many fermented foods [1]. E use of starter cultures is based on the distinctive sensory and technology qualities that they add to the fermented products. Appropriate cultures have been isolated from naturally fermented food for use in industrial production. In addition to their role in food production, starter cultures that produce antimicrobial substances, such as bacteriocins, may serve to prevent food-borne diseases and to increase the shelf-life of foods by reducing/eliminating pathogens and spoilage bacteria in fermented foods, such as sausages [2, 3]. Nisin-producing Lactococcus lactis is applied in fermented foods (mostly dairy products), and it is generally One group of bacteriocins is lantibiotics, which are small, heat-stable, posttranslationally modified bacteriocins [5]. e best examples of lantibiotics are the nisins, which are most commonly produced by Lactococcus lactis strains and include nisins A, F, H, J, Q, U, and Z [6,7,8,9,10,11,12,13].
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