title: Effect of HXT1 and HXT7 hexose transporter overexpression on wild-type and lactic acid producing Saccharomyces cerevisiae cells.
abstract: BACKGROUND
  Since about three decades, Saccharomyces cerevisiae can be engineered to efficiently produce proteins and metabolites. Even recognizing that in baker's yeast one determining step for the glucose consumption rate is the sugar uptake, this fact has never been conceived to improve the metabolite(s) productivity.In this work we compared the ethanol and/or the lactic acid production from wild type and metabolically engineered S. cerevisiae cells expressing an additional copy of one hexose transporter.
  
  
  RESULTS
  Different S. cerevisiae strains (wild type and metabolically engineered for lactic acid production) were transformed with the HXT1 or the HXT7 gene encoding for hexose transporters.Data obtained suggest that the overexpression of an Hxt transporter may lead to an increase in glucose uptake that could result in an increased ethanol and/or lactic acid productivities. As a consequence of the increased productivity and of the reduced process timing, a higher production was measured.
  
  
  CONCLUSIONS
  Metabolic pathway manipulation for improving the properties and the productivity of microorganisms is a well established concept. A high production relies on a multi-factorial system. We showed that by modulating the first step of the pathway leading to lactic acid accumulation an improvement of about 15% in lactic acid production can be obtained in a yeast strain already developed for industrial application.
authors.affiliation: Università degli Studi di Milano-Bicocca, Department of Biotechnology and Bioscience, Piazza della Scienza 2, Milan, Italy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Rossi
authors.forename: Michael
authors.initials: M
authors.lastname: Sauer
authors.forename: Danilo
authors.initials: D
authors.lastname: Porro
authors.forename: Paola
authors.initials: P
authors.lastname: Branduardi
mesh_terms: D015870:Gene Expression; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000378:metabolism; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics* / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000378:metabolism; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D051246:Glucose Transport Proteins, Facilitative; C090594:HXT1 protein, S cerevisiae; C095258:HXT7 protein, S cerevisiae; D009004:Monosaccharide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D019344:Lactic Acid; D005947:Glucose