Biochemical characterization of a novel β-galactosidase from Paenibacillus barengoltzii suitable for lactose hydrolysis and galactooligosaccharides synthesis

A beta-galactosidase gene (PbBGal2A) was cloned from Paenibacillus barengoltzii and expressed in Escherichia coli. The in silica analysis of the deduced amino acid sequences revealed that PbBGal2A shared the highest identity of 40% with the characterized glycoside hydrolase (GH) family 2 beta-galactosidase from Actinobacilius pleuropneumoniae. The recombinant beta-galactosidase (PbBGal2A) was purified with a molecular mass of 124.2 kDa on SDS-PAGE. The optimal pH and temperature of PbBGal2A were determined to be pH 7.5 and 45 C, respectively. PbBGal2A was stable within pH 6.0-8.0 and up to 45 degrees C. It completely hydrolyzed the lactose in milk and whey powder solution. In addition, PbBGal2A exhibited high transglycosylation activity and a maximum yield of 47.9% (w/w) for galactooligosaccharides (GOS) production was obtained in 8 hat a lactose concentration of 350 g/L. These properties make PbBGal2A an ideal candidate for commercial use in the production of lactose-free milk and GOS. (C) 2017 Published by Elsevier B.V.