A Novel Glucose-Tolerant GH1 beta-Glucosidase and Improvement of Its Glucose updates Tolerance Using Site-Directed Mutation

摘要

A novel GH1 beta-glucosidase gene (bgla) from marine bacterium was sequenced and expressed in Escherichia coli. After purification by Ni2+ affinity chromatography, the recombinant protein was characterized. The purified recombinant enzyme showed maximum activity at 40 degrees C, pH 7.5 and was stable between temperatures that range from 4 to 30 degrees C and over the pH range of 6-10. The enzyme displayed a high tolerance to glucose and maximum stimulation at the presence of 100 mM glucose. To improve glucose tolerance of the enzyme, a site-directed mutation (f171w) was introduced into beta-glucosidase. The recombinant F171W showed a higher glucose tolerance than the wild type and maintained more than 40% residual activity at the presence of 4 M glucose. Additionally, the recombinant enzymes showed notable tolerance to ethanol. These properties suggest the enzymes may have potential applications for the fermentation of lignocellulosic sugars and the production of biofuels.