Isolation and characterization of psychrophiles producing cold-active β-galactosidase

Aims: The present study was conducted to screen for psychrophilic micro-organisms that are able to hydrolyse lactose at low temperature, and to examine the cold-active beta-galactosidase produced by the isolated psychrophilic micro-organisms. Methods and Results: Psychrophilic bacteria, which grow on lactose as a sole carbon source, were isolated from soil from Hokkaido, Japan. The phenotype and sequence of 16S rDNA of the isolated strains indicated a taxonomic affiliation to Arthrobacter psychrolactophilus . The isolated A. psychrolactophilus strains were able to grow on lactose at below 5degreesC, and showed cold-active beta-galactosidase activity, which was highly specific at even 0degreesC. Conclusions: Facts in this study may indicate the possibility that the isolated strains produce novel beta-galactosidases that are able to hydrolyse lactose at low temperature, although some strains have isozymes. Significance and Impact of the Study: It may be possible that the cold active beta-galactosidases from the isolated strains can be applied to the food industry, e.g. processing of milk and whey below 5degreesC.