Modes of lactose uptake in the yeast species Kluyveromyces marxianus

Abstract

Twelve lactose-assimilating strains of the yeast species Kluyveromyces marxianus and its varieties marxianus, lactis and bulgaricus were studied with respect to transport mechanisms for lactose, glucose and galactose, fermentation of these sugars and the occurrence of extracellular lactose hydrolysis. The strains fell into three groups. Group I (two strains): Fermentation of lactose, glucose and galactose, extracellular lactose hydrolysis, apparent facilitated diffusion of glucose and galactose; Group II (two strains): Lactose not fermented, glucose and galactose fermented and transported by an apparent proton symport, extracellular hydrolysis of lactose present (one strain) or questionable; Group III (eight strains): Lactose, glucose and galactose fermented, lactose transported by an apparent proton symport mechanism, extracellular hydrolysis of lactose and transport modes for glucose and galactose variable.

Metabolic engineering ofSaccharomyces cerevisiaefor lactose/whey fermentation

“…16 In other Kluyveromyces species lactose uptake has also been described to proceed via a proton symport mechanism. [19][20][21] Lac12p shows sequence similarity to the E. coli xylose and arabinose proton symporters 15 and a significant sequence and structure homology with the S. cerevisiae maltose proton symporter Mal61p, 22 but no significant sequence similarity with the lactose permease (lacY gene) of E. coli. 15 The β-galactosidase (lactase) is encoded by the LAC4 gene 23 and is described to be intracellular.…”

Fed-batch fermentation for production of Kluyveromyces marxianusFII 510700 cultivated on a lactose-based medium

“…Strains of Kluyveromyces or their synonyms, K. fragilis and Saccharomyces fragilis, have been considered the most suitable for bio-conversion of lactose in whey [2,4,20]. However, incomplete or slow fermentations have been observed for many Kluyveromyces strains, when concentrated whey or lactose-enriched substrates have been employed [12,32].…”

Carbon source regulation of β-galactosidase biosynthesis inPenicillium chrysogenum

“…Lactose utilisation in fungi takes place by two ways. Lactose is either hydrolysed extracellularly before or in connection with uptake and the product glucose and galactose are taken up (MORTBERG and NEUJAHR 1986, CARVALHO-SILVA andSPENCER-MARTINS 1990), or lactose is transported into the cell and hydrolysed intracellularly (CAR- VALHO-SILVA and SPENCER-MARTINS 1990, BOZE et al 1987, DICKSON and BARR 1983.Previously we have purified and characterised an intracellular enzyme with β-galactosidase activity (NAGY et al 2001) which implies that in our strain lactose is probably utilised by the consecutive action of lactose permease and β-galactosidase.Here we present our recent results on the production of β-galactosidase and the influence of different carbon sources on the biosynthesis of the enzyme.…”