Biological and Biochemical Exploration of thermal and Glucose Tolerance of Beta-glucosidase A and beta- Glucosidase B from Clostridium thermocellum

Abstract

β-glucosidases (EC 3.2.1.21) are important enzymes involved in the process of cellulose degradation. It is the last enzyme and arguably the most important enzyme in the chain of cellulose hydrolysis, which converts cellobiose to glucose. They are widespread in nature, and have numerous industrial applications, mainly for the production of biofuels. Most β- glucosidases are inhibited by the reaction product glucose resulting in the accumulation of cellobiose. These accumulated cellobiose further inhibit the activities of endoglucanases and exoglucanases, and thereby, limiting the biotechnological and industrial applications of these enzymes such as biofuel production. The thermal stability of β-glucosidases is also an important aspect because industrial purposes require the reactions to be carried out at high temperature. This study provides valuable insights of the kinetics, structure, regulation of glucose tolerance of β-glucosidases and their thermal stability. So, our main aim was to investigate the biochemical properties of BglA and BglB which we have cloned and expressed from Clostridium thermocellum genomic DNA. We also wanted to investigate the glucose tolerance of BglA, B and elucidate its mechanism of inhibition to open up the possibilities of engineering these proteins for the creation of more robust enzymes that are suitable for industrial application of biofuel production.