Enhanced bioethanol production from poplar by Tween 80-assisted acid pretreatment coupled with sulfite detoxification

Acid pretreatment is one of the most prevalent pretreatment methods for bioethanol production by efficiently hydrolyzing hemicellulose and breaking down the dense structure of lignocelluloses. However, it exhibits limited delignification efficiency and produces inhibitors that can obviously hinder the subsequent enzymatic hydrolysis and yeast fermentation. This study developed a novel strategy integrating Tween 80-assisted acid pretreatment with sulfite detoxification to enhance bioethanol production from poplar. Sodium sulfite assistance (2–6 % w/w) in acid pretreatment suppressed inhibitor production, reducing up to 72.8 % furfural and 85.1 % HMF, while dramatically increasing fermentability of unfermentable acid prehydrolysate with at most 6.57 g/L ethanol yielded from 20 g/L glucose. Tween 80 assistance (2–6 % w/w) in acid pretreatment improved xylose extraction to up to 16.91 g/L in prehydrolysate, while increasing the saccharification yield for enzymatic hydrolysis of pretreated substrates by 67.0 %–88.2 %. But it failed to mitigate inhibition during fermentation. In situ detoxification with 6 % sulfite and 6 % Tween 80 in pretreatment enhanced the glucose consumption rate, whereas the enzyme-hydrolyzed glucose yield from pretreated substrates only slightly improved by 4.4 %. Subsequent sulfite detoxification of Tween 80-assisted prehydrolysates showed excellent effect on boosting yeast fermentation. Therefore, subsequent sulfite detoxification was integrated with Tween 80-assisted acid pretreatment with significantly enhanced bioethanol production from pretreated poplar during simultaneous saccharification and fermentation (SSF), increasing yields from 0.31 g/L to 3.13 g/L. This work effectively addressed lignocellulosic recalcitrance and inhibitor generation of acid pretreatment with a combined chemical-additive assistance and post-detoxification strategy to maximize bioethanol productivity from woody biomass.