Comparison of dilute acid and alkali pretreatments in production of fermentable sugars from bamboo: Effect of Tween 80

• NaOH pretreatment was the most efficient pretreatment method for bamboo.
• Effectiveness of Tween 80 in hydrolysis was high at a low cellulase loading.
• Addition of Tween 80 both before and after hydrolysis increased hydrolysis yield.
• Removal of xylan in bamboo by xylanase could further improve efficiency of Tween 80.
• NaOH pretreatment gave the highest sugar recovery followed by SAA pretreatment.

As a fast growing woody grass with high sugar contents, bamboo is a potential material for the production of bio-ethanol, and the saccharification of bamboo has been extensively investigated. However, the role of surfactants on the pretreatment and enzymatic hydrolysis of bamboo has not been clearly elucidated. In this work, effects of aqueous ammonia (SAA), dilute acid (DA), and NaOH pretreatments on the chemical composition, structural features, and enzymatic hydrolysis of bamboo were compared and the effects of Tween 80 on the pretreatments and hydrolysis were explored. NaOH pretreatment showed strong delignification and gave the highest sugar recovery, followed by severe SAA pretreatment (70 °C, 72 h). Total reducing sugars from bamboo with NaOH pretreated bamboo samples were 42.3 g per 100 g dry biomass. With the addition of 3% (w/w) Tween 80, the removal of lignin increased from 9.3% and 54.2% to 13.5% and 57.9% after DA and NaOH pretreatments, respectively. The effectiveness of Tween 80 in enzymatic hydrolysis of different pretreated bamboo was high at a cellulase loading less than 20 FPU/g DM. Addition of Tween 80 both before and after enzymatic saccharification increased hydrolysis yield of bamboo compared to the hydrolysis without Tween 80. The removal of xylan in bamboo by xylanase could further improve the effectiveness of Tween 80, suggesting the importance of the combination of xylanase and Tween 80 in enzymatic hydrolysis of bamboo by cellulases.