Application of the β-glucosidase from the fungus Kretzschmaria zonata on sugarcane bagasse hydrolysis

Abstract β-glucosidases for industrial applications are mainly obtained from filamentous fungi. Kretzschmaria zonata is a phytopathogenic fungus that produces an arsenal of enzymes with biotechnological potential and this work aimed to produce, to purify and to characterize a β-glucosidase from the fungus K. zonata for its application in supplementation of a commercial cocktail for sugarcane bagasse saccharification. The higher specific activity of β-glucosidase was induced by corn cob, 1.085 U/mg of protein. At the end of all purification steps, a purification factor of 6.52 was reached, with an increase of specific activity from 1.22 U/mg, in the crude extract, to 7.97 U/mg. Concerning pH stability, at pH 4, the pH of maximal β-glucosidase activity, the enzyme was completely stable, with 100% of activity after 1 h of incubation, while it kept over than 50% of activity in the pH range from 2.2 to 6. The optimum temperature was 60°C and he half-life times were estimated as 307.8 and 10 min, for temperatures of 60 and 70°C, respectively. The β-glucosidase showed a reduction in relative activity in the presence of 10 mM of manganese sulfate, zinc sulfate, manganese chloride, SDS and glucose, maintaining 55, 56, 62, 70, 73% of the relative activity, respectively. The commercial cocktail supplemented with the K. zonata β-glucosidase enabled the release of 13.89 g/L of glucose and 5.34 g/L of xylose, an increase of 19.8 and 35.5% of glucose and xylose release, respectively, after sugarcane bagasse hydrolysis.