Abstract
The low-cost production of cellulolytic complexes that present high action at mild conditions is one of the major bottlenecks for the economic viability of the production of cellulosic ethanol. The influence of agro-industrial residues was assessed to enhance endoglucanase production by Aspergillus niger 426 grown in solid state fermentation. The highest percentage of lignin degradation was found on soybean hulls (56%) followed by sugarcane bagasse (36%) and rice straw (8.5%). The cellulose degradation, around 90%, was observed on soybean hulls and sugarcane bagasse, but only 50% on rice straw, and maximum production of endoglucanase (112.34 ± 0.984 U mL-1) was observed for soybean hulls. The best Experimental Mixture Design condition was under cultivation of 2.5 g of sugarcane bagasse, 2.3 g of rice straw and 5.2 g of soybean hulls, leading to a maximum activity of 138.92 ± 0.02 U mL-1. The statistical methodology enabled an increase of over 20% in the production of endoglucanase using agro-industrial waste. These data demonstrate that A. niger 426 is a potential source of cellulases which can be obtained by solid state fermentation using agro-industrial waste.
Highlights
IntroductionAgro-industrial residues contain lignocellulosic material available for exploitation as sources of chemical feedstocks, fuels, foods and feeds
The central point was composed of a 33.33% ternary mixture of each supporting substrate
The experiments were performed in triplicate, and differences smaller than 10% were obtained for endoglucanase, as well as for residual reducing sugars concentrations
Summary
Agro-industrial residues contain lignocellulosic material available for exploitation as sources of chemical feedstocks, fuels, foods and feeds. The major component of lignocellulose is cellulose, which is the most abundant renewable organic resource, and comprises approximately 30–50% of the dry weight of lignocellulose (Harris & DeBolt, 2010). Cellulose is the major component of agro-industrial waste. Agro-industrial residues can be used as a carbon source to produce enzymes, especially holocellulases. Within this group of enzymes, endoglucanases have important roles in the hydrolysis of holocellulose (Segato, Damásio, de Lucas, Squina, & Prade, 2014). Cellulases are relatively costly enzymes, and a significant reduction in cost will be important for their commercial use in biorefineries. Cellulase-based strategies that will make the biorefinery processing more economical include: increasing commercial enzyme volumetric productivity, producing enzymes using cheaper substrates and producing cellulases with higher specific activity on solid substrates (Ekwe, Morgenstern, Tsang, Storms, & Powlowski, 2013; Hingsamer & Jungmeier, 2019)
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