KOH/urea pretreatment of bagasse for ethanol production without black liquor or wastewater generation

Alkaline pretreatment is a simple and effective method for removing lignin at low temperatures and normal pressure, but this process consumes large amounts of water and produces wastewater, both of which limit its industrial applications. To develop a process with zero discharge of black liquor and wastewater, in this study, KOH/urea-treated bagasse was directly subjected to enzymatic hydrolysis without detoxification or washing after adjusting the pH. Adaptive Laboratory Evolved (ALE) Saccharomyces cerevisiae Y2034, which can endure three-fold diluted black liquor, was obtained. The results showed that SCB treated with 1.5% KOH/urea (1.5% KOH/1.5% urea) for 4 h could be directly enzymatically hydrolyzed and fermented. The enzymatic hydrolysis efficiency and ethanol yield reached 89.9% and 97%, respectively. The cellulosic ethanol production method developed in this research provides a possibility for industrial application. • Direct enzymolysis and fermentation of unwashed KU-treated SCB were performed. • The domesticated yeast strain maintained a high fermentation ability. • Ethanol was produced from KU-treated lignocellulose without black liquor discharge. • The enzymatic hydrolysis efficiency and ethanol yield reached 89.94% and 96.99%.