Study On Detoxification And Concentration Of Corn Stover Acid-catalyzed Hydrolysate And Its Use For Ethanol Fermentation

Acid-catalyzed hydrolysis to produce fermentable sugar is one of the key procedures in the production of fuel ethanol from lignocellulose,such as corn stover.However,this process is faced with a series of challenges,such as acid recovery,inhibition of byproducts and so on.This study combined the acid retardation and continuous-effect membrane distillation(CEMD)process and optimized the process conditions on the basis of the previous studies,to realize separation of sugar and acid and removal of fermentation inhibitors in the acid-catalyzed hydrolysate,enrichment of dilute sugary-containing stream and dilute acid-containing stream,and verified its feasibility for ethanol fermentation.This study used acid retardation process to conduct the experiment of separating sugar and acid in the acid-catalyzed hydrolysate of corn stover.The results showed that acid retardation process could effectively separate sugar and acid in the hydrolysate.And the recovery rate of sulfuric acid and glucose were 99.12%and98.92%,respectively.Meanwhile,the process also removed most of the fermentation inhibitors in the hydrolysate,the removal rate of phenolic compounds was 92.50%,the organic acids and furans inhibitors were completely removed basically.This study discussed the feasibility of deeply concentrating the aqueous acid eluent and aqueous sugar eluent,obtained from the acid retardation process,by using CEMD technology.The experimental results indicated that the aqueous sugar eluent could be concentrated around 5 times by using CEMD process.The rejection rate of glucose kept 100%during the whole process.The largest permeation flux and gained output ratio(GOR)in the process were 4.84 L/(m~2·h)and 15.27,respectively,which corresponded to the energy saving effect of a conventional eighteen-effect evaporator.In the aqueous acid eluent depth enrichment experiments,the sulfuric acid was eventually concentrated to 43.43 wt%,and the GOR still kept 6.43.This study tested the effects of inoculation size,agitation rate,temperature,initial pH and glucose content on the performance of ethanol fermentation and obtained the optimal fermentation conditions.And ethanol fermentation experiments from the hydrolysate were conducted under the optimal fermentation conditions by using Saccharomyces cerevisiae CICC 1308.Over the course of 24 h,the culture produced 43.06 g/L ethanol with a yield of 86.31%and a productivity of 1.79 g/(L·h),and the glucose utilization rate reached 97.95%.The ethanol production and yield reached 91.06%and 92.71%of the corresponding values(47.29 g/L and 93.10%)in the control experiments(glucose as carbon source),respectively.This study showed that the integration of acid retardation and CEMD process can be effectively used to the production of fuel ethanol with the corn stover.