Pretreatment Technologies Of Corn Straw Based On Delignification And Its Influence On Enzymatic Hydrolysis Efficiency

Crop straw is a cheap and easy availability renewable biomass resource with abundant reserves,it can be used to obtain cellulosic ethanol and basic chemicals through a series of processes such as pretreatment,enzymatic hydrolysis,and fermentation.Developing cellulosic ethanol technologies is an effective way to solve energy shortage and resource scarcity,it can not only help rural revitalization,but also accelerate the process of achieving carbon peaks and carbon neutrality.However,there are complex chemical bonds between the cellulose,hemicellulose and lignin in the straw,and they are tightly entangled to form a dense structure.Therefore,the development of economically feasible pretreatment technologies is the key to the commercial production of cellulosic ethanol.In order to realize the utilization of the full components of straw,acid sulfite and eutectic solvent pretreatment technologies of corn straw were in-depth studied.The influence of pretreatment process on component separation and cellulose enzymatic hydrolysis efficiency was revealed in this article,and the optimized pretreatment technology was researched.Firstly,the acid sulfite method is used to separate the components of straw at a lower p H,and improve the efficiency of straw enzymatic hydrolysis.Meanwhile,the lignin can transform to lignosulfonate by sulfonation.The orthogonal experiment was designed to pretreat corn straw when the liquid-to-solid ratio was 3 and 6,but because the liquid-to-solid ratio of 3 was too low,the reaction solution and the straw were not fully contacted,resulting in poor pretreatment effect.When the liquid-to-solid ratio is 6,the corn straw have been fully reacted,the microscopic morphology characterization of the straw shows that as the liquid ratio increases,the surface of the straw becomes rougher and more irregular.When the dosage of dilute sulfuric acid is 0.50%(w/w),and the dosage of sodium bisulfite is 4%(w/w),pretreatment at 160°C for 90 minutes,the removal rate of hemicellulose in corn straw reached more than 90%,and the removal rate of lignin reached 55%.When the CTech ? cellulase loading is 15 FPU/g-glucan,the enzymatic hydrolysis efficiency reaches 87.6%.Compared with corn straw obtained by commercial steam explosion method,less cellulase is used when reaching the same enzymolysis efficiency,which reduces the cost of enzymatic hydrolysis and saccharification.The increase in the amount of dilute sulfuric acid and sodium bisulfite during pretreatment is beneficial to the degradation of hemicellulose and the sulfonation and dissolution of lignin.With the decrease of hemicellulose content and lignin content in corn straw,the enzymatic hydrolysis efficiency of cellulose increased accordingly.Secondly,in view of the high reaction pressure and high temperature in the pretreatment process,the large loss of cellulose from corn straw,and the problem that the reagents used in acid sulfite pretreatment are not recyclable,a recyclable eutectic solvent was used to pretreat corn stalks under normal pressure.Amides,alcohols and organic acids choline chloride-based eutectic solvents and new acidic eutectic solvents containing benzene rings were synthesized to pretreat straw,as the hydrogen donor in the choline chloride-based eutectic solvents from the weaker acid amides and alcohols replaced by stronger acidic organic acids.The enhancement of the acidity of the eutectic solvent significantly improves the removal rate of hemicellulose and lignin in the straw.The synthesized new acidic eutectic solvent containing benzene ring can solubilize lignin,catalyze the rupture of lignin chemical bonds and promote lignin dissolution under appropriate acidity,and highly retain cellulose components TMBAC/Ts OH eutectic solvent was synthesized.After pretreatment of corn stover at 80 ? for 0.5 h,the removal rate of lignin reached 81.0%,the retention rate of cellulose was 94.1%.When the enzyme loading was 15 FPU/g-glucan,the enzymatic hydrolysis efficiency reached 81.2%.The acid sulfite pretreatment technology is used to efficiently separate the components of corn straw,and a high level of enzymatic hydrolysis efficiency is achieved at a lower enzyme load.The eutectic solvent pretreatment technology is used to pretreatment corn straw at normal pressure with lower temperature and shorter time.We provided a new idea for the development of corn straw pretreatment technologies.