title: Lactose utilization by Saccharomyces cerevisiae strains expressing Kluyveromyces lactis LAC genes.
abstract: Whey generated in cheese manufacture continues being an industrial problem without a satisfactory solution. Genetic modification of the yeast S. cerevisiae to obtain strains able to utilize lactose, is a prerequisite for the utilization of this yeast to convert cheese whey into useful fermentation products (i.e. biomass, heterologous protein and other recombinant products). Although the construction of S. cerevisiae Lac(+) strains has been achieved by different strategies, most of these strains have unsuitable characteristics, such as genetic instability of the Lac phenotype or diauxic growth. In previous communications we have described the construction of genetically stable strains of S. cerevisiae that assimilate lactose with a high efficiency. These strains carry multiple copies of Kluyveromyces lactis LAC4 and LAC12 genes, which code for a beta-galactosidase and a lactose permease, respectively. In this work we report additional results about the effect of gene dosage, and analyze the performance of a selected strain in the bioconversion of cheese whey. Additionally, we describe the construction of a new strain, which combines the Lac(+) phenotype with additional properties of biotechnological interest: flocculence, and the ability to hydrolyze starch.
authors.affiliation: Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones Científicas, Apartado de correos 73, E46100, Valencia, Burjassot, Spain. marta@dada.jci.tju.edu
authors.forename: M
authors.initials: M
authors.lastname: Rubio-Texeira
authors.forename: M
authors.initials: M
authors.lastname: Arévalo-Rodríguez
authors.forename: J L
authors.initials: JL
authors.lastname: Lequerica
authors.forename: J
authors.initials: J
authors.lastname: Polaina
mesh_terms: D002611:Cheese / Q000382:microbiology; D029968:Escherichia coli Proteins; D018628:Gene Dosage; D015966:Gene Expression Regulation, Fungal; D006868:Hydrolysis; D007218:Industrial Microbiology / Q000379:methods; D007716:Kluyveromyces / Q000201:enzymology / Q000235:genetics*; D007763:Lac Operon / Q000502:physiology*; D007785:Lactose / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008894:Milk Proteins / Q000378:metabolism; D009004:Monosaccharide Transport Proteins; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D013213:Starch / Q000378:metabolism; D027981:Symporters; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D008894:Milk Proteins; D009004:Monosaccharide Transport Proteins; D027981:Symporters; D013213:Starch; C021499:lactose permease; D001616:beta-Galactosidase; D007785:Lactose