Enhanced production of nisin by co-culture of Lactococcus lactis sub sp. lactis and Yarrowia lipolytica in molasses based medium

•Nisin is a commercial, FDA and EC approved bacteriocin and produced by Lactococcus lactis sub sp. Lactis at industrial scale.•Co-culture is defined as incubation of different certain microbial strains under aseptic conditions to metabolize the substrate(s) together.•As a novel approach for nisin production, Yarrowia lipolytica co-cultured with L. lactis sub sp. Lactis in a sugar beet molasses based medium.•Sugar beet molasses is a cheaper carbon source compared to maltose and whey, that were already used in co-cultivation and nisin production.•In the mixed culture used, nisin production and L. lactis growth were 50% and 49% higher than that of pure culture, respectively. L. lactis

Nisin is a safe, approved and commercial bacteriocin that is produced by Lactococcus lactis subsp. lactis. Since lactate accumulation in fermentation medium reduces L. lactis growth and nisin production, Yarrowia lipolytica, a lactate consuming yeast and L. lactis subsp. lactis, were simultaneously cultured in a molasses based medium. Y. lipolytica is not able to consume sucrose as carbon source, but rather consumes lactate and hence decrease lactic acid titer by 10% in the medium. Lactic acid consumption, 15% increased pH value and stimulated L. lactis growth. In the mixed culture, nisin production and L. lactis growth were 50% and 49% higher than that of pure culture, respectively. Also the results showed that specific growth rate of L. lactis increased 4 times more than that of the pure culture.