Screening and Characterization of β-glucosidase Producing Bifidobacterium animalis subsp. lactis LT19-2 Isolated from Infant Feces

Abstract

β-glucosidase (E.C 3.2.1.21) catalyzes hydrolysis of β-glucosidic natural compounds such as genistein and ginsenoside. The aglycone moiety, a result of hydrolysis, has enhanced bioavailability and potent physiological effects such as antitumor and anti-inflammation. As probiotics, bifidobacteria are major intestinal microflora in human and have several health promoting effects to host. They also have genes associated with carbohydrate modifying enzymes and play an important role in carbohydrate fermentation in the colon of host. Bifidobacteria which can produce β-glucosidase lead to synergistic health benefits and have useful application benefits. Nevertheless, there is less research on screening and characterization of bifidobacteria with β-glucosidase. The aim of this study is screening and characterization of Bifidobacterium animalis subsp. lactis LT19-2 with β-glucosidase activity. B. animalis subsp. lactis LT19-2 had one chromosome with a 1,923,614 bp and a G + C content of 60.49 %. The chromosome contained total 1,610 genes that included 1,551 of CDSs (coding sequences) and 59 of RNA genes. RNA genes contained 52 of tRNA, and 6 of rRNA. Whole genome sequencing of B. animalis subsp. lactis LT19-2 revealed that they had two β-glucosidase encoding genes, bglA and bglB. BglA and BglB were categorized as GH (glycosyl hydrolase)1 and GH3, respectively. The enzymes were purified by ammonium precipitation, DEAE sepharose fast flow, and sephadex G-100. Purification fold of purified BglA and BglB was 10.6 times and 13.25 times higher than that of the crude extract, respectively. The reactive conditions such as pH, temperature and metal ions with purified enzyme were optimized. Also, enzyme kinetic parameters were calculated by linear plot of Lineweaver-Burk equation. In this study, B. animalis subsp. lactis LT19-2 with β-glucosidase activity was successfully screened. Additionally, to optimize the reactive condition of β-glucosidases, β-glucosidases from B. animalis subsp. lactis LT19-2 were purified and investigated. The conversion of glucosides using probiotics such as bifidobacterium might be valuable process in industry. Especially, B. animalis subsp. lactis LT19-2 with β-glucosidase could lead to increased bioavailability and physiological effects as well as indigenous probiotic effects of Bifidobacterium strain.