Improvement of hydrolysis and fermentation of sugarcane bagasse by soaking in aqueous ammonia and methanolic ammonia.

Sugarcane bagasse was pretreated by soaking it in aqueous ammonia (SAA) and methanolic aqueous ammonia (SMAA) at 70 °C for 12 h. Then the pretreated as well as untreated bagasse was subjected to enzymatic hydrolysis at 50 °C for 72 h by 15 FPU cellulase and 30 CBU cellobiase per g of substrate. The hydrolysis of SAA-pretreated bagasse with a solid to liquid (S:L) ratio of 1:10 resulted in 95.9% of the maximum theoretical yield. The production yield for SMAA at an S:L ratio of 1:6 with 15% methanol was 88.6%, while it was only 21.3% for the untreated bagasse. Ethanol production by simultaneous saccharification and fermentation was conducted at 37 °C for 72 h. The results revealed that the ethanol production yield was improved from 12.7% for the untreated bagasse to 92.45% and 90.8% for the SAA and the SMAA pretreated bagasse, respectively. The compositional and chemical structural analysis suggested that lignin removal and crystallinity reduction were responsible for the hydrolysis and SSF improvements.