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Presence of galactose in precultures induces lacS and leads to short lag phase in lactose-grown Lactococcus lactis cultures
- Lorántfy, Bettina, Johanson, Anna, Faria-Oliveira, Fábio, Franzén, Carl Johan, Mapelli, Valeria, Olsson, Lisbeth
- Journal of industrial microbiology & biotechnology 2019 v.46 no.1 pp. 33-43
- Lactococcus lactis, antiporters, galactose, gene expression regulation, genes, lactic acid bacteria, lactose, starter cultures, transferases
- Lactose conversion by lactic acid bacteria is of high industrial relevance and consistent starter culture quality is of outmost importance. We observed that Lactococcus lactis using the high-affinity lactose-phosphotransferase system excreted galactose towards the end of the lactose consumption phase. The excreted galactose was re-consumed after lactose depletion. The lacS gene, known to encode a lactose permease with affinity for galactose, a putative galactose–lactose antiporter, was upregulated under the conditions studied. When transferring cells from anaerobic to respiration-permissive conditions, lactose-assimilating strains exhibited a long and non-reproducible lag phase. Through systematic preculture experiments, the presence of galactose in the precultures was correlated to short and reproducible lag phases in respiration-permissive main cultivations. For starter culture production, the presence of galactose during propagation of dairy strains can provide a physiological marker for short culture lag phase in lactose-grown cultures.