Detailed study of efficient ethanol production from elmwood by alkali pretreatment

• Hardwood elm was successfully used as a feedstock for ethanol production.
• Alkaline treatment modified the wood structure and improved ethanol production.
• Tween-20 improved the enzymatic hydrolysis and fermentation yield.
• Adsorption and desorption of enzymes were related to enzymatic hydrolysis yield.

An alkaline pretreatment was performed on hardwood elm to improve enzymatic hydrolysis and ethanol production. The pretreatment was conducted with 8% (w/v) NaOH solution at 0, 25, and 80 °C for 2 h, and the best results were obtained by the pretreatment at 0 °C. The glucose yield from untreated wood was only 8.0% and improved to 71.5% after the pretreatment at 0 °C, whereas the corresponding ethanol yield was improved from 11.1% to 45.7%. In order to decrease ineffective adsorption of cellulase enzyme on lignin and enhance the enzymatic hydrolysis and fermentation yields, a non-ionic surfactant, Tween-20, was used in the hydrolysis process. The addition of 2.5 g L−1 Tween-20 further favorably modified the yields of enzymatic hydrolysis and ethanol production to 79.8% and 57.3%, respectively. Changes in the wood’s structural properties by the pretreatment were followed in detail by swelling and buffering capacity measurements as well as SEM and FTIR analyses. Furthermore, the adsorption and desorption of cellulase during the enzymatic hydrolysis were investigated, and a consistent relation was observed between adsorbed and desorbed enzymes and enzymatic hydrolysis yield.

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