Thermotolerant Yeast Strains Producers of Galacto-Oligosaccharides

ABSTRACT

Twenty five thermotolerant yeasts isolated from different dairy products were tested for 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/mg protein, 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.

Keywords:

• Kluyveromyces yeasts
• β-galactosidase
• galacto-oligosaccharides (GOS)
• whey
• transgalactosylation