| Pretreatment is one of the most important steps in biomass utilization,but the enzymatic conversion of lignocellulosic biomass still has a lack of economical and effective technologies for pretreatment.As an important platform compound,γ-valerolactone(GVL)has been recognized as a safe and sustainable organic solvent,and it could be used in biomass pretreatment to disrupt the complex structure of lignocelluloses and improve the degradability of biomass.However,the γ-valerolactone pretreatment still had less report,and the structural feature and hydrolysis characteristics of pretreated agriculture is still not clear.Therefore,systematic study of γ-valerolactone pretreatment could improve the development of pretreatment technology and it was benefited to the utilization of three compounds from lignocellulosic materials.In this study,the different acid(sulfuric acid and sodium hydrogen sulfate)and different acid concentration(25 m M,50 m M and 75 m M,150 m M)were added to the γ-valerolactone/water system to pretreat corn stover.And the different pretreatment temperature(120 °C and 160 °C)also been investigated.The results show that the catalysis of sulfuric acid was better than that of sodium bisulfate,75 m M sulfuric acid pretreatment(120 °C)could remove 62.7% and 62.7% of hemicellulose and lignin,cellulose content was increased to 57%.Increased the concentration of sulfuric acid to 150 m M,the content of xylose was only 4.69%,and the removal rate was 92%.However,results showed that the pretreatment had inhibition effect on hydrolysis of Avicel,the hydrolysis yield of pretreated Avicel had a significant decrease.Actually,the inhibition on cellulose could been alleviated by alkaline-treat and the addition of additive(Tween 80).Structure characterization showed that the crystallinities of pretreated corn stover were increased,pretreatment could removing a large amount of lignin and hemicellulose and caused significant damage to the structure of lignocellulosic materials,which were benefited to the hydrolysis of cellulose.In addition,the effects of lignins on hydrolysis were further studied.The results show that the acid insoluble lignin has inhibitory effect on hydrolysis of Avicel,but the γ-valerolactone lignin had no negative effect on hydrolysis,the lignin which isolated from low concentration acid(25 m M 和 50 m M)pretreatment in γ-valerolactone/water system even has obvious promoting effect on hydrolysis of Avicel(the glucose yield was increased from 25.53% to 41.29%and 39.05%).Besides,hydrophobic property and adsorption properties of lignins also been investigated.At lower acid concentration,γ-valerolactone lignin had higher hydrophobicity and higher strength of binding to cellulases,but its maximum adsorption capacity was smaller than acid insoluble lignin.The Fourier infrared spectra analysis of lignin was found to γ-valerolactone lignin had a high degree of preservation of the lignin structure,which was benefit for the utilization of lignin. |
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