The level of pyruvate-formate lyase controls the shift from homolactic to mixed-acid product formation in Lactococcus lactis

C.R. Melchiorsen, K.V. Jokumsen, John Villadsen, H. Israelsen, J. Arnau

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Regulation of pyruvate-formate lyase (PFL) activity in vivo plays a central role in the shift from homolactic to mixed-acid product formation observed during the growth of Lactococcus lactis on glucose and galactose, respectively. Characterisation of L lactis MG1363 in anaerobic batch cultures showed that the specific in vivo activity (flux) of PFL was 4-fold higher in L. lactis cells grown with galactose, compared with cells grown with glucose. The change in the PFL flux correlated with the observed variation in the PFL enzyme level, i.e. the PFL enzyme level was 3.4-fold higher in L. lactis cells grown on galactose than in those grown on glucose. To investigate whether a variation in the level of PFL was responsible for the shift in pyruvate metabolism, L. lactis strains with altered expression of pfl were constructed. The pfl gene was expressed under the control of different constitutive promoters in L. lactis MG1363 and in the PFL-deficient strain CRM40. Strains with five different PFL levels were obtained. Variation in the PFL level markedly affected the resulting end-product formation in these strains. During growth on galactose, the flux towards mixed-acid products was to a great extent controlled by the PFL level. This demonstrates that a regulated PFL level plays a predominant role in the regulation of the metabolic shift from homolactic to mixed-acid product formation in L lactis.
    Original languageEnglish
    JournalApplied Microbiology and Biotechnology
    Volume58
    Issue number3
    Pages (from-to)338-344
    ISSN0175-7598
    Publication statusPublished - 2002

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