Thermotolerant yeast strains producers of galacto-oligosaccharides

Abstract

Twentyfive thermotolerant yeasts isolatedfrom different dairy products were testedfor their ability to grow on lactose containing media and to produce β-galactosidase enzyme with enhanced transgalactosylation activity. It was confirmed that the most effective strains are those belonging to the genus Kluyveromyces. Two K. marxianus strains - 904 and t3 with relatively high specific activity of β-galactosidase (480 and 500 U/mgprotein, respectively) were selected. It was shown that these strains possess a high yield of lactose transformation (hydrolysis and transgalactosylation) (98%) and high tri-and tetra-galacto-oligosaccharides (GOS) yield. More than 50% conversion rate of lactose to GOS was achieved when K. marxianus 904 and t3 were used as whole cell biocatalysts. The composition of the synthesized GOS was determined to be exclusively consisted of galactosyl residues.