Optimization of endoglucanase production by Cellulomonas sp

Commercial ethanol is currently produced from conventional feedstock such as sugarcane and cornstarch, but lignocellulosic waste such as sugarcane bagasse and wood industry residues can be used. Cellulases play a fundamental role to convert cellulose into fermentable sugars. From a screening of a collection of cellulolytic bacterial strains isolated from different biomes, a strain of Cellulomonas sp. from Misiones, Argentina, was selected. In this work, cellulase production by Cellulomonas sp. was optimized using sugarcane bagasse as carbon source. A Plackett-Burman experimental design was conducted to evaluate the influence of 12 variables in endoglucanase production. The variables evaluated were: pH, temperature, substrate and inoculum concentration, concentration of nitrogen sources: yeast extract, peptone, ammonium sulphate and sodium nitrate and concentration of the salts: K₂HPO₄, MgSO₄, KCl and FeSO₄. Flasks were incubated at 150 rpm and after 48, 72 and 96 hours of fermentation, samples were removed and the endoglucanase activity was determined. Sugarcane bagasse and KCl concentration and pH were the significant variables. Using these variables, a Central Composite Rotatable Design (CCRD) 2³ was performed to optimize endoglucanase production. Sugarcane bagasse and KCl concentration ranged from 0.3 to 3.0% (w/v) and 0.3 to 1.0 g/L, respectively and pH from 6 to 9. The best endoglucanase activity was obtained after 72 h of cultivation (0.29 U/mL). The conditions that maximized the endoglucanase activity were: KCl 0.65 g/L, sugarcane bagasse 1.25 % (w/v) and pH 7.8. At this combination, the maximum predicted yield was 0.29 U/mL.