| Pretreatment of lignocellulosic materials is a critical step in the production of cellulosic ethanol because it can significantly break the structure of lignocellulose and remove part of lignin to improve the hydrolysis efficiency of cellulose.In this study,the microwave-assisted pretreatment method was applied to pretreat corn stover as an alternative to conventional pretreatment methods.After pretreatment,the effect of acid type,acid concentration,microwave radiation time and microwave intensity on lignin removal rate and hydrolysis efficiency of pretreated substrate was studied by the single-factor experimental method,and the optimal pretreatment conditions were obtained,which provided the foundation for the low cost and efficient conversion of lignocellulose materials to fuel ethanol.In this research,used the single factor variable method,corn stover that was pretreated under the condition of 1wt%H2SO4,140℃ and 40 min,was used as raw materials to study the high efficiency cellulose complex system by the single factor control method.The objective of this study is to improve the overall efficiency of this enzyme complex system,thus reduce the total enzyme loading and the cost of cellulosic ethanol production.The impacts of different enzyme loadings and different enzyme ratios were investigated to illustrate the influence of xylanase and pectinase on different hydrolysis substrates in this enzyme complex system.An optimized enzyme complex system was established based on this research.The research results show that:1)The optimal pretreatment conditions were obtained using a method of single factor experiment.The objective of this study is to provide research foundation for fuel ethanol production from lignocellulosic materials by a low cost and high efficiency method.The results indicated that maleic acid and citric acid shown the best performance in terms of increasing cellulose hydrolysis conversion among the small molecular organic acids tested in this research.When using maleic acid assisted microwave pretreatment,the reducing sugar yield achieved the highest of 51.1%under the conditions of 15%acid concentration,200w microwave intensity,and 8 minutes treatment.In comparison,when citric acid are used,the reducing sugar yield achieved the highest of 39.8%under the condition of 15%acid concentration,400w microwave intensity,and 8 minutes treatment.The total sugar conversion increased 135.6%and 81.7%compared to untreated corn stover during enzymatic hydrolysis.The pretreatment results and SEM images revealed that the micro structure of corn stover was noticeably changed when microwave-assisted organic acid pretreatment was used,which increased the porosity of lignocellulose and the accessibility of cellulases.As a result,microwave-assisted organic acid pretreatment dramatically improved the enzymatic hydrolysis efficiency and the conversion of pretreated corn stover.2)the hydrolysis conversion increased with the increasing of the total protein content.However,in order to control the enzyme cost,a protein loading of 30mg was used as the optimal condition in this study.The reducing sugar yield was 69.2%when the ratio of cellulase,β-glucosidase and xylanase was 1:2:1,while it was 67.8%when the ratio of cellulase,β-glucosidase,xylanase and pectinase was 1:2:1:1.3)Although xylanase and pectinase were proved to improve enzymatic hydrolysis conversion in previous papers,their effects were obvious in this study due to the slight hemicellulose content in the substrate used.Our results further indicated that the supplementation of xylanase and pectinase should be based on the structural carbohydrate content in the hydrolysis substrates. |
