The Inhibition Of Steam Explosion By-Products On Cellulosic Ethanol Conversion And The Effect Of Bio-Detoxification

Fuel ethanol production from lignocellulosic materials is an effective way to relief fossil energy crisis. The lignocellulosic materials must be pretreated before hydrolysis in cellulosic ethanol conversion. However, some byproducts released from pretreatment process may inhibit the enzymic hydrolysis or fermentation. The influences of the inhibitors liberated from steam explosion, which is the widely used pretreated method, was detected in this study. Based on the inhibition result, fungi FLZ10 was used for removing the inhibitors and biodetoxification was further studied.At first, the surface structures of corn-stovor were observed by AFM technology, to prove the results of breaking the compact lignocellulosic structures after pretreatment. According to the analysis of hydralysates, the effects of the byproducts to the fermentation were studied. It was showed that the ethanol yield were strongly inhibited by Mg²⁺and Fe²⁺, the decrease of ethanol yield is 34% and 11%respectively. As the total salts decreased, the ethanol yield has reduced. It has no obvious influence on the ethanol yield when the concentration of formic acid≤2g/L and furfural≤1g/L.The ethanol yield has been inhibited when the concentration of acetic acid≥15g/L and 5-HMF≥2.0g/L, the decrease of ethanol yield is 92% and 54%respectively, but the low concentration have promotion to the fermentation.Secondly, according to the studies of inhibition, the removals of inhibitors with FLZ10 have been studied. The removal rate of inorganic ions, Ca²⁺,Mg²⁺,Al³⁺,Fe²⁺are 70%,50%,90%,80%.When T=35℃,t=96h,the removal rate of organics, acetic acid,propionic acid,butyric acid are 24%,31%,28% in the culture medium with glucose as carbon source.. In the actual fermentation, the effect of bio-detoxification and washing detoxification were equivalent. The ethanol yield using bio-detoxification based washing detoxification is 50g/L.Once more, the optimizations of culture medium of FLZ10 agent have been carried out. As standards for monitoring cellulase activity, CB and FPA activities were detected, and the concentrations of inhibitors in corn-stover washing water, including formic acid,acetic acid,furfural,5-HMF,were detected for the bio- detoxification ability. The results were performed that the CB and FP activities in 50℃were higher than they were in 40℃, and the removal rates of inhibitors in 40℃were higher than they were in 50℃. The culture medium which using SBR or EGSB effluent as nutrients abtained the best rate for removing acetic acids; The culture medium of entire wheat bran was turned out the most replacement of formic acid,furfural and 5-HMF. However, there were little differences in inhibitors removing rate among different culture medium. Based on the comprehensive analysis, cheap crystalline cellulose (Avicel ) can be replaced by cheap corn stover powder in thedetoxified bioagent medium.At last, contribution of growth factors was performed. According to orthogonal analysis ,it showed that the effects of growth factors rang from strong to weak were pantothenic acid > Co > VB1 > Zn > Mn > Ni > inositol, the optimized actual concentration were NiCl2·6H2O 50μm/L,MnCl2·4H2O 25mg/L,ZnSO4·7H2O 6mg/L,CoCl2·8H2O 30μm/L,inositol 150mg/L,pantothenic acid10ml/L,VB1150mg/L.