Improvement of fungal cellulolytic and xylanolytic enzymes production by new formulation of culture medium using wastes

Abstract

The use of the I-Optimal mixture design technique of agro-industrial residues in cultivation submerged at 28°C for 15 days with Trichoderma reesei QM 9414, complemented with nutrients, was used to optimize the mixture for the production of fibrolytic enzymes. The results demonstrated that the use of 100% (m/v) of brewer's spent grain was promising for the production of total cellulases (0.42 FPU/mL) and xylanase (39.60 U/mL), as well as the use of 33.3% citrus pulp and 66.7% brewer's spent grain for the production of xylanase (40.2 U/mL). The combination of 16.67% wheat bran, 16.67% citrus pulp, and 66.7% brewer's spent grain was the most promising for the production of endoglucanase (2.03 U/mL), exoglucanase (3.20 U/mL), and β-glycosidase (0.12 U/mL). The study on the demand for minerals, sucrose, and yeast extract (as a vitamin and amino acid source) revealed that 0.1% yeast extract, 0.11% dibasic potassium phosphate, 0.0028% zinc, and 1% of sucrose in 12 days of culture were sufficient to maximize the production of cellulases, increasing by 2.38 times (1.0 FPU/mL) compared to the initial culture (0.42 FPU/mL). Cellulolytic production remained the same with the use of 0.01% tween 80 in citrus pulp (0.40 FPU/mL) compared to that obtained in the design with a brewer's spent grain without tween 80, however it reduced substantially (from 15 to 9 days) the cultivation time. On the other hand, the use of tween 80 dramatically inhibited the fungal production of xylanases (2.96 U/mL). The best combination of salts was combined with tween 80 to obtain 1.12 FPU / mL in 9 days of fermentation. An enzymatic hydrolysis of cassava bagasse was carried out by combining cellulases and amylases, reaching 48 g / L of reducing sugar. Thus, this work shows that by studying the influence of residues, kind of salts and concentration of tween 80, a more efficient and economical bioprocess was possible to obtain, as well as the association between fibrolytic enzymes.