Studies On The Characteristics Of Lignocellulose Degradation During The Process Of Enzymatic Saccharification And Anaerobic Digestion

Bioconvesioin of lignocellulosic feedstock into bio-energy is an important way to solve the energy crisis. In this paper, the process of lignocellulose enzymatic hydrolysis focused on three main aspects. To explore the enzyme production laws, and also optimize fermentation parameters to construct a microbial consortium cultured in liquid condition which can produced amounts of effective extracellular enzyme. The results was found that in the condition of4L/min ventilator capacity,3%of substrate loading rate and0rpm stirring rate, the highest enzyme activity was obtained, in which CMCase was3.43IU/ml and xylanase was15.18lU/ml. The crude enzyme produced by WSD-5was good in enzymatic saccharification and the consortium itself also had good acidification ability. The maximum concentration of reducing sugars was3254mg/L after48h saccharification. The concentration of sCOD peaked on day2with a value of4345mg/L during acidification, and the biogas yield and methane yield were22.3%and32.3%higher than un-acidified samples. According to the different characteristics of temperature for microbial consortium growth (30-35℃) and the enzymatic optimum temperature (50-55℃), a new approach was established for enzymatic saccharification. The concentration of total reducing sugar by this approach was15times higher than the traditional method. It was also found that the higher hemicellulose content in lignocellulosic materials, the lower conversion rate was obtainedInvestigating biological pretreatment of lignocellulosic materials by three microbial consortia (MCI, WSD-5and XDC-2) followed by saccharification and anaerobic digestion, to determine the optimum pretreatment time and enzyme loading rate for highest lignocellulose conversion rate. Wheat straw conversion rate of24.1%and76.3%was obtained after3and7days pretreatment by the consortium WSD-5under low and high loadings of commercial enzyme mixtures, and56.1%was the highest yield of wheat straw which pretreated by consortium MCI under moderate enzyme loading rate. Napier grass pretreated by the consortium MC1gave65.9%and83.2%total sugar yield under moderate and high loadings of commercial enzyme mixtures, while the highest yield was43.3%pretreated by the consortium WSD-5under a low enzyme loading. The maximum methane yield of pretreated samples by the consortia MCI, WSD-5and XDC-2were1.39,1.49and1.32times greater than the values of the untreated controls.During the lignocellulose anaerobic digestion, it was the key to efficiently hydrolyze lignocellulose into small molecular organic matters. It was explored the hydrolysis characteristics of cellulose and hemicellulose and also the effect of temperature and sludge on anaerobic digestion. The results showed that hemicellulose was easier to degrade under mesophilic temperature while cellulose can be hydrolyzed better under high temperature. At thermophilic temperature, the total volume biogas and methane generated by each substrate are higher than in mesophilic anaerobic fermentation. Hemicellulose and cellulose ratio of4:0and3:1, produced methane volumes were1763.4and1588.2ml. The difference of hemicellulose content (cellulose:hemicellulose was1:3and0:4) in mesophilic and thermophilic temperature was not significant, the cellulose to hemicellulose content of1:3and0:4 produced methane volume was1547.3and1301.7ml, respectively. Based on the results above, it could be considered that higher hemicellulose content substrates was better for mesophilic temperature fermentation, and for high temperature anaerobic digestion, relatively high cellulose containing substrate could be considered.