Integrated Strategies to Enhance Cellulolytic Enzyme Production Using an Instrumented Bioreactor for Solid-State Fermentation of Sugarcane Bagasse

Abstract

The conversion of agro-industrial residues, such as sugarcane bagasse, into high-value products and renewable energy, within the biorefinery concept, is a potential alternative towards the sustainable management of these resources. This work evaluates the production of cellulolytic enzymes by a selected strain of Aspergillus niger cultivated in sugarcane bagasse under solid-state fermentation using an instrumented lab-scale bioreactor. The effects of environmental factors including the type of substrate and medium composition, as well as the operational conditions (air flow rate, inlet air relative humidity, and initial substrate moisture content) on the production of the enzymatic complex were evaluated using statistical design tools. Significant increases in FPase, endoglucanase, and xylanase activities were achieved under the optimized conditions predicted by the models, with values of 0.88, 21.77, and 143.85 IU/g of dry solid substrate, respectively, representing around ten-, four-, and twofold increases compared to the activities obtained under the initial growth conditions. This demonstrates the importance of evaluating environmental and operational criteria in order to achieve efficient enzyme production. The crude enzymatic extract obtained under optimized conditions was employed for enzymatic hydrolysis of pretreated sugarcane bagasse. Approximately 13 % of total reducing sugars, and a glucose concentration of 2.54 g/L, were obtained after 22 h of hydrolysis of steam exploded sugarcane bagasse, indicating that the enzymatic cocktail produced has good potential for use in the conversion of biomass.