Applied Biochemistry and Biotechnology, Vol.191, No.1, 444-462, 2020
Comprehensive Optimization of Culture Conditions for Production of Biomass-Hydrolyzing Enzymes of Trichoderma SG2 in Submerged and Solid-State Fermentation
Lignocellulose biomass contain large macromolecules especially cellulose and hemicelluloses that can be converted to fuel and chemicals using microbial biocatalysts. This study presents comprehensive optimization of production of biomass-hydrolyzing enzymes (BHE) by a high beta-glucosidase-producing Trichoderma SG2 for bioconversion of lignocellulose biomass. Overall, a mixture of paper powder and switchgrass was most suited for production of BHE in submerged fermentation (SmF). BHE production was significantly different for various organic and inorganic nitrogen sources. The combination of peptone, yeast extract, and ammonium sulfate resulted in the highest activities (Units/mL) of BHE: 9.85 +/- 0.55 cellulase, 38.91 +/- 0.31 xylanase, 21.19 +/- 1.35 beta-glucosidase, and 7.63 +/- 0.31 beta-xylosidase. Surfactants comparably enhanced BHE production. The highest cellulase activity (4.86 +/- 0.55) was at 25 degrees C, whereas 35 degrees C supported the highest activities of xylanase, beta-glucosidase, and beta-xylosidase. A broad initial culture pH (4-7) supported BHE production. The T-opt for cellulase and xylanase was 50 degrees C. beta-xylosidase and beta-glucosidase were optimally active at 40 and 70 degrees C, respectively; pH 5 resulted in highest cellulase, beta-glucosidase, and beta-xylosidase activities; and pH 6 resulted in highest xylanase activity. Response surface methodology (RSM) was used to optimize major medium ingredients. BHE activities were several orders of magnitude higher in solid-state fermentation (SSF) than in SmF. Therefore, SSF can be deployed for one-step production of complete mixture of Trichoderma SG2 BHE for bioconversion of biomass to saccharide feedstock.