title: Construction of a flocculent Saccharomyces cerevisiae strain secreting high levels of Aspergillus niger beta-galactosidase.
abstract: A flocculent Saccharomyces cerevisiae strain secreting Aspergillus niger beta-galactosidase activity was constructed by transforming S. cerevisiae NCYC869-A3 strain with plasmid pVK1.1 harboring the A. niger beta-galactosidase gene, lacA, under the control of the ADH1 promoter and terminator. Compared to other recombinant S. cerevisiae strains, this recombinant yeast has higher levels of extracellular beta-galactosidase activity. In shake-flask cultures, the beta-galactosidase activity detected in the supernatant was 20 times higher than that obtained with previously constructed strains (Domingues et al. 2000a). In bioreactor culture, with cheese-whey permeate as substrate, a yield of 878.0 nkat/gsubstrate was obtained. The recombinant strain is an attractive alternative to other fungal beta-galactosidase production systems as the enzyme is produced in a rather pure form. Moreover, the use of flocculating yeast cells allows for enzyme production with high productivity in continuous fermentation systems with facilitated downstream processing.
authors.affiliation: Centro de Engenharia Biológica-IBQF, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: L
authors.initials: L
authors.lastname: Domingues
authors.forename: J A
authors.initials: JA
authors.lastname: Teixeira
authors.forename: M
authors.initials: M
authors.lastname: Penttilä
authors.forename: N
authors.initials: N
authors.lastname: Lima
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology*; D019149:Bioreactors; D002611:Cheese / Q000382:microbiology; D005427:Flocculation; D007785:Lactose / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D001616:beta-Galactosidase / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D001616:beta-Galactosidase; D007785:Lactose