A comparison of fermentation strategies for cellulosic ethanol production from NaOH-soaked sugarcane bagasse at high solid loading with decreased cellulase loading

NaOH-soaked sugarcane bagasse (ASSB) could be converted into monosaccharides by low cellulase loading at a solid loading of 2%. However, different initial solid loading affected the enzymatic convertibility. Therefore, the effects of solid and cellulase loadings were investigated in this work. Four fermentation strategies, simultaneous saccharification and fermentation (SSF), fed-batch SSF, semi-SSF, and fed-batch semi-SSF were conducted and compared. The results showed that cellulose convertibility decreased with increased initial solid loading from 1.9 to 7.5% in a linear manner. However, the decrease was not obvious when 10% of initial solid was loaded compared to that of 7.5%. Based on the enzymatic hydrolysis at a constant cellulose dose, 7.5 FPU/g dry matter, the initial solid loading of 10% was selected for the fed-batch fermentations. The final ethanol yields among the fermentations showed no significant differences. Presaccharification increased the ethanol productivity when the presaccharification time was not counted. Glycerol concentration in fermentations with the presaccharification stage was higher than those without this stage.