Utilization of agroindustrial residues for producing cellulases by Aspergillus fumigatus on Semi-Solid Fermentation

Abstract

Agroindustrial biomasses (sugarcane bagasse, green coconut husk and cashew apple bagasse) are used as substrate for producing cellulases by Aspergillus fumigatus on Semi-Solid Fermentation (SSF). The untreated lignocellulosics and fermented sugarcane bagasse are characterized using the National Renewable Energy Laboratory (NREL) protocols analysis as well as through Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) assays. A two-variable central composite rotatable design (CCRD) coupled to response surface methodology (RSM) with three experiments at center point are used to investigate the influence of initial moisture and pH on carboxymethycellulose and filter paper, i.e., CMCase and FPase activities produced by the Aspergillus fumigatus using all of the three lignocellulosic biomasses. Results show that sugarcane bagasse has the highest cellulose content and the cashew apple bagasse the highest lignin content, approximately 46.0%. Additionally, pH and moisture (linear and quadratic parameters), as well as their combination, play a key role on both CMCase and FPase activities. The highest values for CMCase and FPase are 4.20 U/g and 0.64 U/g for sugarcane bagasse; 4.07 U/g and 0.28 U/g for coconut husk and 0.64 U/g and 0.32 U/g for cashew apple bagasse. The use of SSF for producing cellulases can be an option for reducing energy consumption due to reduction on the steps during biomass pretreatment.