Rewiring Lactococcus lactis for Ethanol Production

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    Abstract

    Lactic acid bacteria (LAB) are known for their high tolerance toward organic acids and alcohols (R. S. Gold, M. M. Meagher, R. Hutkins, and T. Conway, J. Ind. Microbiol. 10:45–54, 1992) and could potentially serve as platform organisms for production of these compounds. In this study, we attempted to redirect the metabolism of LAB model organism Lactococcus lactis toward ethanol production. Codon-optimized Zymomonas mobilis pyruvate decarboxylase (PDC) was introduced and expressed from synthetic promoters in different strain backgrounds. In the wild-type L. lactis strain MG1363 growing on glucose, only small amounts of ethanol were obtained after introducing PDC, probably due to a low native alcohol dehydrogenase activity. When the same strains were grown on maltose, ethanol was the major product and lesser amounts of lactate, formate, and acetate were formed. Inactivating the lactate dehydrogenase genes ldhX, ldhB, and ldh and introducing codon-optimized Z. mobilis alcohol dehydrogenase (ADHB) in addition to PDC resulted in high-yield ethanol formation when strains were grown on glucose, with only minor amounts of by-products formed. Finally, a strain with ethanol as the sole observed fermentation product was obtained by further inactivating the phosphotransacetylase (PTA) and the native alcohol dehydrogenase (ADHE).
    Original languageEnglish
    JournalApplied and Environmental Microbiology
    Volume79
    Issue number8
    Pages (from-to)2512-2518
    ISSN0099-2240
    DOIs
    Publication statusPublished - 2013

    Keywords

    • Glucose
    • Optimization
    • Organic acids
    • Ethanol
    • Alcohol dehydrogenase
    • Alcohol dehydrogenase activity
    • Ethanol production
    • Fermentation products
    • Lactate dehydrogenase genes
    • Lactic acid bacteria
    • Phosphotransacetylase
    • Pyruvate decarboxylase

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