An acid-tolerant and cold-active β-galactosidase potentially suitable to process milk and whey samples

A novel beta-galactosidase gene (gal(M)) was cloned from an aquatic habitat metagenome. The analysis of its translated sequence (Gal(M)) revealed its phylogenetic closeness towards Verrucomicrobia sp. The sequence comparison and homology structure analysis designated it a member of GH42 family. The three-dimensional homology model of Gal(M) depicted a typical (beta/alpha)8 TIM-barrel containing the catalytic core. The gene (gal(M)) was expressed in a heterologous host, Escherichia coli, and the purified protein (Gal(M)) was subjected to biochemical characterization. It displayed beta-galactosidase activity in a wide range of pH (2.0 to 9.0) and temperature (4 to 60 degrees C). The heat exposed protein showed considerable stability at 40 and 50 degrees C, with the half-life of about 100 h and 35 h, respectively. The presence of Na, Mg, K, Ca, and Mn metals was favorable to the catalytic efficiency of Gal(M), which is a desirable catalytic feature, as these metals exist in milk. It showed remarkable tolerance of glucose and galactose in the reaction. Furthermore, Gal(M) discerned transglycosylation activity that is useful in galacto-oligosaccharides' production. These biochemical properties specify the suitability of this biocatalyst for milk and whey processing applications.

Automated summary

A novel beta-galactosidase gene was cloned from an aquatic habitat metagenome, and its characteristics were studied. The protein encoded by this gene exhibited beta-galactosidase activity across a wide range of pH and temperature. It also showed efficient catalytic activity in the presence of certain metal ions and displayed tolerance to glucose and galactose. In addition, it had transglycosylation activity for the production of galacto-oligosaccharides. These properties make it a promising biocatalyst for milk and whey processing applications.