Corn Straw Expansion Pretreatment And The Research Of Reducing Sugar By Enzymatic Hydrolysis

To obtain fuel ethanol from crop straw is a new hotspot of clean energy. It’s difficult to reduce sugar from crop straw because the main component of straw, cellulose, hemicellulose and lignin closely together and the high crystallinity of cellulose. Therefore, the structure of crop must be destroyed before fermentation.In the present study, the corn straw as the representative of straw resources. The corn straw was pretreated by expansion technology. Compared with crushed corn straw, scanning electron microscope pictures showed that the corn straw fiber bundle was destroyed and the wrapped function of lignin was weaken. X-ray diffraction showed the crystalline degree of cellulose decreased by 14.57%. The characteristic peak of composition and group changed obviously after expansion pretreatment. The part of hemicellulose and lignin was hydrolysised. And the molecular structure of cellulose was destroyed. The characterization analysis showed that pretreatment can effectively increase the extruded cellulose enzyme accessibility.This paper studied cellulose enzyme fermentation process. Firstly, we carried out the training of LNSJ-1bacteria, then we carried out solid fermentation to obtain enzyme. Based on the result of the single factor experiment, with enzyme active response value, central composite rotatable design according to the principles surface methodology was carried out to optimize the enzyme fermentation process. Model analysis was performed with the help of SAS software and the optimum values of the three factors were obtained which was pH of 5.3, solid-liquid radio1:2, inoculation of 22.7%. In this process conditions, enzyme active is 486U/g.Compared with crushed corn straw, the expended corn straw was hydrolysised by enzyme. Based on the result of the single factor experiment, with sugar yield response value, central composite rotatable design according to the principles surface methodology was carried out to optimize the hydrolysis process. Model analysis was performed with the help of SAS software and the optimum values of the five factors were obtained which was temperature of 49℃, pH of 4.6, enzyme concentration of 36.5U/g, substrate concentration of 107g/L, reaction time of 22.4h. In this process conditions, the sugar yield is 0.285 g/g.Analysised hydrolysised sugar liquid by ion Chromatography concluded that glucose was 0.170g from 1g expended corn straw; the proportion was 59.6% of total sugar yield. And xylose was 0.047g; the proportion was 25% of total sugar. By measuring each compont’s percentage of expended corn straw before hydrolysis and after hydrolysis showed that cellulose utilization was 59.15%, hemicellulose utilization was 29.97% and little lignin was used by enzyme.