Holocellulase production by filamentous fungi: potential in the hydrolysis of energy cane and other sugarcane varieties

Abstract

Economic interest in sugarcane bagasse has significantly increased in recent years due to the worldwide demand for sustainable energy production. The use of sugarcane bagasse for holocellulase production has been a strategy for bioconversion of lignocellulosic residues into second-generation ethanol. The fungi secrete to the culture medium a cocktail of enzymes necessary to convert biomass into nutrients. Thus, this study aimed to analyze the production profile of holocellulases from Aspergillus and Humicola species, Trichoderma reesei RP698, and Mycothermus thermophilus grown in sugarcane bagasse, culm of energy cane, and culm of sugarcane SP80-3280. The capacity of the enzymatic pools in the hydrolysis of cell walls of these sugarcane varieties was also verified. M. thermophilus was the best producer of endoglucanase, cellobiohydrolase, β-glucosidase, xylanase, β-xylosidase, xyloglucanase, arabinanase, arabinofuranosidase, mannanase, and acetyl xylan esterase. T. reesei RP698 also produced and secreted a wide range of holocellulases to the medium. The saccharification of sugarcane bagasse, energy cane, and sugarcane SP80-3280 by the enzymatic cocktails obtained from M. thermophilus released 0.87 ± 0.05 mg.mL−1, 0.88 ± 0.07 mg.mL−1, and 1.10 ± 0.08 mg.mL−1 of reducing sugars, respectively. However, the application of T. reesei RP698 extracts showed a release of 0.85 ± 0.03 mg.mL−1, 0.40 ± 0.03 mg.mL−1, and 0.83 ± 0.03 mg.mL−1 of reducing sugars. Therefore, T. reesei RP698 and M. thermophilus showed to be good holocellulase producers, and their crude extracts presented a great capacity for the hydrolysis of the different kinds of sugarcane residues.