Abstract
Effective pretreatment is vital to improve the biomass conversion efficiency, which often requires the addition of xylanase as an accessory enzyme to enhance enzymatic saccharification of corn stover. In this study, we investigated the effect of two sophisticated pretreatment methods including ammonium sulfite (AS) and steam explosion (SE) on the xylanase profits involved in enzymatic hydrolysis of corn stover. We further explored the interactions between lignin and xylanase Xyn10A protein. Our results showed that the conversion rates of glucan and xylan in corn stover by AS pretreatment were higher by Xyn10A supplementation than that by SE pretreatment. Compared with the lignin from SE pretreated corn stover, the lignin from AS pretreated corn stover had a lower Xyn10A initial adsorption velocity (13.56 vs. 10.89 mg g−1 min−1) and adsorption capacity (49.46 vs. 27.42 mg g−1 of lignin) and weakened binding strength (310.6 vs. 215.9 L g−1). Our study demonstrated the low absolute zeta potential and strong hydrophilicity of the lignin may partly account for relative weak interaction between xylanase protein and lignin from AS pretreated corn stover. In conclusion, our results suggested that AS pretreatment weakened the inhibition of lignin to enzyme, promoted the enzymatic hydrolysis of corn stover, and decreased the cost of enzyme in bioconversion.
Highlights
The bioconversion process of lignocellulosic biomass to bioethanol under environmentally friendly, low-energy consumption and mild process conditions has been widely studied in the past decades (Kumar et al, 2008; Bilal et al, 2017)
Previous studies indicated that steam explosion (SE) pretreatment effectively degraded hemicellulose with little lignin elimination and resulted in an increase in the lignin content of the pretreated corn stover (Brownell et al, 1986; Rahikainen et al, 2013a)
The partial removal of lignin may weaken the negative effect of lignin on enzymatic hydrolysis and increase the contents of cellulose and hemicellulose in pretreated corn stover after ammonium sulfite (AS) pretreatment
Summary
The bioconversion process of lignocellulosic biomass to bioethanol under environmentally friendly, low-energy consumption and mild process conditions has been widely studied in the past decades (Kumar et al, 2008; Bilal et al, 2017). The low substrate saccharification efficiency limit its industrial application because of the recalcitrance of native lignocellulose and the Pretreatments Change Lignin Adsorption Behavior high cost of lignocellulose-degrading enzymes (cellulase and hemicellulase) (Berlin et al, 2005). Pretreatment is an indispensable step in the bioconversion of lignocellulosic materials, which efficiently destroyed the tight lignocellulose structure and improved enzymatic digestibility (Tan et al, 2013; Karimi and Taherzadeh, 2016). The different pretreatments improve the enzymatic digestibility of lignocellulosic materials through different mechanisms involved in the part removal of chemical components (mainly hemicellulose or lignin), increased surface area of substrate, and decreased crystallinity of cellulose (Liu et al, 2017; Ying et al, 2018). Hemicellulose is relatively modest degradation, and part of the lignin is converted to lignosulfonate, which increased hydrophilicity of lignin (Wang et al, 2013; Tan et al, 2015)
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