Dataset Information

Presence of galactose in precultures induces lacS and leads to short lag phase in lactose-grown Lactococcus lactis cultures.

ABSTRACT: 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.

SUBMITTER: Lorantfy B

PROVIDER: S-EPMC6339885 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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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 B Johanson Anna A Faria-Oliveira Fábio F Franzén Carl Johan CJ Mapelli Valeria V Olsson Lisbeth L

Journal of industrial microbiology & biotechnology 20181109 1

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 upregulat ...[more]

PMID: 30413923

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Project description:BackgroundCheese ripening is a complex, time consuming and expensive process, which involves the generation of precursors from carbohydrates, proteins and fats and their subsequent conversion into a wide range of compounds responsible for the flavour and texture of the cheese. This study aims to investigate production of cheese aroma compounds outside the cheese matrix that could be applied for instance as food supplements in dairy or non-dairy products.ResultsIn this study, aroma formation by a dairy Lactococcus lactis was analysed as a function of the growth medium [milk, hydrolysed micellar casein isolate (MCI) and chemically defined medium (CDM)] and the cultivation conditions (batch culture, retentostat culture and a milli-cheese model system). In the retentostat cultures, the nutrient supply was severely restricted resulting in low growth rates (~ 0.001 h-1), thereby mimicking cheese ripening conditions in which nutrients are scarce and bacteria hardly grow. In total 82 volatile organic compounds were produced by the bacteria. Despite the use of a chemically defined medium, retentostat cultures had the biggest qualitative overlap in aroma production with the milli-cheese model system (36 out of 54 compounds). In the retentostat cultures, 52 known cheese compounds were produced and several important cheese aroma compounds and/or compounds with a buttery or cheese-like aroma increased in retentostat cultures compared to batch cultures and milli-cheeses, such as esters, methyl ketones, diketones and unsaturated ketones. In cultures on CDM and MCI, free fatty acids and their corresponding degradation products were underrepresented compared to what was found in the milli-cheeses. Addition of a mixture of free fatty acids to CDM and MCI could help to enhance flavour formation in these media, thereby even better resembling flavour formation in cheese.ConclusionsThis study demonstrates that retentostat cultivation is the preferred method to produce cheese flavours outside the cheese matrix by mimicking the slow growth of bacteria during cheese ripening.

Dataset Information

Presence of galactose in precultures induces lacS and leads to short lag phase in lactose-grown Lactococcus lactis cultures.

Publications

Presence of galactose in precultures induces lacS and leads to short lag phase in lactose-grown Lactococcus lactis cultures.

Similar Datasets

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