Combined Effect Of Microwave And P.chrysosporium Pretreatments Of Distillers Grains For Fermentable Sugars By Enzymatic Hydrolysis

With the depletion of the fossil energy and the demand of the global energy,lignocellulosic biomass has become very important as a promising raw material for bioethanol.Distillers grains(DG),is riched in lignocellulose,which is one of the most abundant food processing byproducts producing from white spirit brewage in China.Using DG as the raw material to prepare the fermentable sugar for ethanol production,is not only beneficial to recycling of DG,but also can promote the recycle development of traditional distillery.DG was used as the raw material to prepare the fermentable sugar for ethanol production in this thesis.The combined effect of microwave and p.chrysosporium pretreatments on DG enzymatic hydrolysis was carried out.The main research contents are as follows:(1)The optimum enzymatic conditions were studied on the basis of the effects of time and dosage for cellulase and xylanase on enzymolysis yield.The results showed that the holocellulose content was reached up to 50% in DG,which has a good potential for preparation of fermentable sugars.Adding 1000 U/g cellulase,500 U/g xylanase and 1 U/g beta-glycosidase acted 24 h,reducing sugar yield can reach 13.52%,xylose yield up to 1.51%.Three enzymes added at the same time,shows good synergistic effect,is a suitable enzyme composition for DG.(2)the effect of the solid liquid ratio,microwave power and time of microwave pretreatment parameters on the enzymatic hydrolysis yield were studied,the influence of microwave processing conditions are optimized by the response surface design.The optimal microwave pretreatment condition was identified as solid-liquid ratio 1:10,microwave power100 W,time 3 min.Under this condition,the reducing sugar yield was 19.74% and xylose yield was 2.41%.(3)Regarding lignin degradation enzyme activity and enzymatic hydrolysis yield and lignin degradation rate as the indexes,determined the P.chrysosporium time and dosage.The results showed that,adding 10% P.chrysosporium acted 6 days,Lac was 61.88 U/L,MnP was440.08 U/L and LiP was 146.61 U/L.At this point,the reducing sugar and xylose yield were17.61% and 3.08%,respectively.The lignin degradation rate was 1.31%.(4)The influence of pretreatment order on enzymolysis yield was studied by combining the microwave and P.chrysosporium pretreatments.The DG characteristics changes were studied by component analysis and apparent structure.The results suggested that the combination of microwave and P.chrysosporium pretreatment is effective in improving the enzymatic hydrolysis efficiency of DG.But the order of pretreatments had no significant difference.Under the combined effect of both of them reducing sugar and xylose yield were reached up to 25.21% and 25.21% respectively.The Scanning electron microscopy(SEM),X-diffraction(XRD)and fourier-transform infrared spectrometry(FTIR)results showed that the residual surface became increasingly coarse,the gaps between cellulose fibers were visible,and many pores were developed,part of the lignin was degraded.