Exploration of novel salt-tolerant β-galactosidases for GOS synthesis based on whole genome sequencing of Bacillus hwajinpoensis Zjut HJ2101

Microbial β-galactosidases have been regarded as efficient biocatalysts in manufacturing galacto-oligosaccharides (GOS), which are widely recognized prebiotics. Salt-tolerant β-galactosidases can digest plant polysaccharides and synthesize GOS under high-salt conditions. In this study, five novel β-galactosidase-encoding genes in the genome of a new screened salt-tolerant Bacillus hwajinpoensis Zjut HJ2101 (16 S rRNA GenBank No. PP601097) were identified via whole-genome sequencing. Comparative analysis of the specific activities of the five β-galactosidases (β-gal1-5) revealed that β-gal5 exhibited the highest specific activity. In addition, β-gal5 maintained > 60% of its activity after being exposed to 1.25 mol/L sodium chloride solution for one hour. Moreover, β-gal5 efficiently hydrolyzed 400 g/L lactose to yield 36.8% GOS at 40℃ and pH7.0. The results of this study indicate that β-gal5 derived from B. hwajinpoensis Zjut HJ2101 can be regarded as a promising biocatalyst for GOS production, and could be used to industrial food manufacturing in high-salt environments.