Comparative study of simultaneous saccharification and fermentation byproducts from sugarcane bagasse using steam explosion, alkaline hydrogen peroxide and organosolv pretreatments

Abstract

Byproducts of simultaneous saccharification and fermentation (SSF) from sugarcane bagasse using steam explosion (SE, 190 °C for 10 min and 210 °C for 5 min) and green liquor (GL) combined with hydrogen peroxide (GL–H₂O₂) or ethanol (GL–ethanol) pretreatments were compared. Results showed that SE pretreatments did not result in lactic acid because a majority of the glucose was consumed for yeast growth and ethanol production, and the ethanol yield of 93.86% (of the theoretical) at 190 °C for 10 min and 94.33% at 210 °C for 5 min were achieved. Most of the hemicelluloses were removed and more acetyl groups were generated after the SE pretreatment, so it always had the highest amount of acetic acid (1.22 g L⁻¹ at 190 °C for 10 min and 1.38 g L⁻¹ at 210 °C for 5 min). GL–ethanol pretreatment resulted in an ethanol yield of 80.56%. However, the existence of reactive lignin from organic solvent produced high amount of byproducts, especially for the maximum glycerol contents (0.818 g L⁻¹). Deficient lignin removal and sugar degradation with GL–H₂O₂ pretreatment led to the lowest ethanol yield of 23.23%, which may be because some inhibitors generated from GL–H₂O₂ pretreatment affected hydrolysis efficiency and yeast activity in the SSF process.