Expression and characterization of β-galactosidase from fecal microbes of Rhinopithecus bieti

Abstract:

[Objective] The study was to express and characterize β-galactosidase from the fecal microbes of Rhinopithecus bieti. [Methods] A β-galactosidase gene galRBM20_1 was cloned from the fecal microbial metagenome of Rhinopithecus bieti. The pEASY-E2-galRBM20_1 plasmid was constructed and transformed into Escherichia coli BL21 (DE3). The expression was induced by Isopropyl β-D-1-thiogalactopyranoside and the enzymatic properties were studied.[Results] The optimum pH of β-galactosidase galRBM20_1 was 5.0, and the enzyme retained more than 70% activity between pH 4 and 7. The optimum temperature is 45℃ and the enzyme was stable at 37℃ and 45℃, retaining nearly 100% activity after incubation for 1 h. In addition, the enzyme had strong NaCl stability. After 1 h of 1 to 5 mol/L NaCl treatment, the relative enzyme activity maintained 100%; when the concentration of NaCl was 4 mol/L, the activity of β-galactosidase galRBM20_1 was the highest (146%); it still had activity after treatment with 2.5 mol/L NaCl at 45℃ for 24 h. [Conclusion] β-galactosidase galRBM20_1 has good salt tolerance and wide pH range.