Cold-active acid β-galactosidase activity of isolated psychrophilic-basidiomycetous yeast Guehomyces pullulans

SummaryIn the present study, psychrophilic yeasts, which grow on lactose as a sole carbon source at low temperature and under acidic conditions, were isolated from soil from Hokkaido, Japan. The phenotypes and sequences of 28S rDNA of the isolated strains indicated a taxonomic affiliation to Guehomyces pullulans. The isolated strains were able to grow on lactose at below 5 °C, and showed cold-active acid β-galactosidase activity even at 0 °C and pH 4.0 in the extracellular fractions. Moreover, Km of β-galactosidase activity for lactose in the extracellular fraction from strain R1 was found to be 50.5 mM at 10 °C, and the activity could hydrolyze lactose in milk at 10 °C. The findings in this study indicate the possibility that the isolated strains produce novel acid β-galactosidases that are able to hydrolyze lactose at low temperature.