Bioconversion of Sweet Sorghum Residues by Trichoderma citrinoviride C1 Enzymes Cocktail for Effective Bioethanol Production

Abstract

Improved cost-effective bioethanol production using inexpensive enzymes preparation was investigated. Three types of waste lignocellulosic materials were converted—for the production of enzyme preparation, a mixture of sugar beet pulp and wheat bran, while the source of sugars in hydrolysates was sweet sorghum biomass. A novel enzyme cocktail of Trichoderma citrinoviride C1 is presented. The one-step ultrafiltration process of crude enzyme extract resulted in a threefold increase of cellulolytic and xylanolytic activities. The effectiveness of enzyme preparation, compared to Cellic® CTec2, was tested in an optimized enzymatic hydrolysis process. Depending on the test conditions, hydrolysates with different glucose concentrations were obtained—from 6.3 g L−1 to 14.6 g L−1 (representing from 90% to 79% of the CTec2 enzyme yield, respectively). Furthermore, ethanol production by Saccharomyces cerevisiae SIHA Active Yeast 6 strain DF 639 in optimal conditions reached about 120 mL kg d.m.−1 (75% compared with the CTec2 process). The achieved yields suggested that the produced enzyme cocktail C1 could be potentially used to reduce the cost of bioethanol production from sweet sorghum biomass.