title: Rewiring Lactococcus lactis for ethanol production.
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).
authors: Department of Systems Biology, Center for Systems Microbiology, Technical University of Denmark, Kongens Lyngby, Denmark. cso@bio.dtu.dk
authors: Christian
authors: C
authors: Solem
authors: Tore
authors: T
authors: Dehli
authors: Peter Ruhdal
authors: PR
authors: Jensen
mesh_terms: D000426:Alcohol Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D002244:Carbon / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005798:Genes, Bacterial; D005818:Genetic Engineering; D005947:Glucose / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D013294:Lactococcus lactis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D008320:Maltose / Q000378:metabolism; D010709:Phosphate Acetyltransferase / Q000235:genetics; D011401:Promoter Regions, Genetic; D011767:Pyruvate Decarboxylase / Q000235:genetics* / Q000378:metabolism; D017355:Zymomonas / Q000201:enzymology / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D000431:Ethanol; D008320:Maltose; D002244:Carbon; D000426:Alcohol Dehydrogenase; D007770:L-Lactate Dehydrogenase; D010709:Phosphate Acetyltransferase; D011767:Pyruvate Decarboxylase; D005947:Glucose
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