A new beta-galactosidase with a low temperature optimum isolated from the Antarctic Arthrobacter sp. 20B: gene cloning, purification and characterization.

A psychrotrophic bacterium producing a cold-adapted beta-galactosidase upon growth at low temperatures was classified as Arthrobacter sp. 20B. A genomic DNA library of strain 20B introduced into Escherichia coli TOP10F' and screening on X-Gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside)-containing agar plates led to the isolation of beta-galactosidase gene.