Corn Core Hemicellulosic Hydrolyzate Preparation And Use Of Xylose Fermentation Ethanol

Ethanol is an environmentally friendly renewable liquid fuel. Ethanol receives generally attention as the succedaneum of petrolic.But the traditional technology of ethanol production is to use crop and wheat which are starchiness as raw materials of ethanol fermentation. It can't sustainable development because of the restriction of food security. Production of fuel ethanol utilizing lignocellulose has been one focus of energy source exploitation. D-xylose is the most abundant monosaccharide in lignocellulose hydrolysates. Ethanolic fermentation of xylose is one of key technology for the efficient utilization of lignocellulose hydrolysates to produce fuel ethanol. In this study, corncob was used as raw materials of ethanol fermentation, approached the possible of ethanol production with corncob hemicellulose hydrolysates which was fermented by Candida shehatae HDYXHT-01. Meanwhile, the hydrolysis craft, detoxification craft and the fermentation craft of Candida shehatae HDYXHT-01 were studied.The optimum hydrolysis craft was determined according to single factor experiments, CCD(Central Composit Design) and Response Surface Analysis with Design-Expert 7.1.3 software. When the material and liquid ratio was 1:10, the optimum hydrolysis condition was: 119.8℃, 1.5h, 1.16% H2SO4 (v/v). Under this hydrolysis craft, 20g hydrolyzated corncob which was open-air dried could obtain 5.93g xylose, and 0.31g xylose was obtained by per gram dry corncob.Mix detoxification method was applied to the detoxification of hemicellulose hydrolysates. The effects of boiling , CaO and activated charcoal were researched in the detoxificating process. Furfural was removed completely, 24.60% of acetic acid was removed and 99.1% of phenols was removed when the concentration of GH-15 was 5%. The fermentation craft of the xylose utilizing strain Candida shehatae HDYXHT-01 was optimized. Single factor experiments and Plackett-Burman design were used to evaluate the influences of all related factors in fermentation craft. The results showed that (NH4)2SO4, KH2PO4, yeast extract and inoculum volume were the main affecting factors while the other additives had no significant effects on ethanol fermentation. The optimum fermentation craft was determined according to CCD (Central composit Design) and Response Surface Analysis with Design-Expert 7.1.3 software. The optimal fermentation craft were (NH4)2SO4 0.36g/L, KH2PO42.68g/L, yeast extract 2.59g/L, inoculum volume 9.67%. Other fermentation conditions were xylose 80g/L, MgSO4·7H2O 0.1g/L, pH4.8 ,and 250mL flask containing 80mL medium which was cultivated at 30℃for 48h and the agitation speed was 140r/min.Under this fermentation craft, ethanol productivity was 26.10g/L, which was 1.5 times of initial.A 5L bioreactor was used to study the ethanol fermentation, the productivity of ethanol reached 19.8g/L, xylose fermented rate 67.14%, ethanol yield 0.37 and ethanol production rate 0.41g/(L·h) in the optimized operating conditions.Hemicellulose hydrolysates which was at the concentration of 40g/L was prepared into medium and adjusted pH4.8, pH5.0 and pH5.2 before fermentation ,after which the ethanol cocentration was 8.26g/L, 11.73 g/L and 14.82g/L separately.Corncob hemicellulose hydrolysates can be fermented to ethanol by strain Candida shehatae HDYXHT-01, which laid a foundation to ethanol production by this strain.