Studies On The Productions Of Isopropanol And Butanol From Low-cost Biomass By Hydrolyzation And The In Situ Extractive Fermentations Of These Alcohols Using Liquid-liquid Extraction

Many energy studies turned attention to environment-friendly renewable energy,since the crude oil was gradual exhausted,and to deal with the requirements of environment protection.The exploitation of biomass energy is an important way of the renewable energy researches.Ethanol,propanol,and butanol were considered to be the most potentially liquid biofuels,which have some good features that were stable physical and chemical properties,easily burnable,high-energy density,can be used as fuel or fuel additive.However,a lot of factors have been hindered the biological production of these alcohols,including the shortage of the fermentable carbon source,the alcohol tolerance limitation of the alcohols producing strain,and the difficulties in alcohols extraction process from fermentation broth.To overcome these difficulties faced in alcohols production process,converting cheap cellulosic biomass into fermentable sugar,improving the manufacturing processes of alcohols,and the studies of the extraction or recovery of alcohols were carried out.Fermentable sugar was achieved on the concentration level of 20.70 g/L,by hydrolyzing cassava bagasse using 2.0 % dilute sulfuric acid with 121 ? for 120 minutes,and the hydrolysis rate was 24.35 %.Lignocellulose in cassava bagasse has been successfully converted into the monosaccharides which can be used directly by microbe,by the most simple and effective method mentioned above.Clostridium beijerinckii ATCC 6014 could produce alcohols using cassava bagasse hydrolysate as carbon source,the productions of isopropanol and butanol were 6.69 g/L and 12.31 g/L,respectively.The total production,yield,volumetric productivity were 18.52 g/L,0.46 g/g,0.31 g/L/h,respectively.The results demonstrate the feasibility and potential of dilute sulfuric acid treated cassava bagasse hydrolysate in alcohols production.In order to find the low-cost production methods of carbon source for the alcohols producing strain,co-culturing Phanerochaete chrysosporium and Trichoderma reesei was carried out for the production of lignocellulolytic enzymes,using the sugarcane bagasse as the substrate which was pretreated by steam explosion,and the lignocellulolytic enzymes were used for the degradation and saccharifying of these pretreated sugarcane bagasse.The production of monosaccharides was obtained by 11.34 g/L from the enzymatic hydrolysis,the hydrolysis rate of raw material was 14.18 %.The productions of isopropanol and butanol were 5.45 g/L and 11.29 g/L,respectively,by the immobilized-cell fermentation with sugarcane bagasse hydrolysate.The total production,yield,volumetric productivity were 16.74 g/L,0.48 g/g,0.27 g/L/h,respectively.The low-cost productions of the lignocellulolytic enzymes and the fermentable sugars have been achieved.In addition,it also showed that the process of enzymes production,sugarcane bagasse hydrolysis,and alcohols production could be carried out consecutively.The production process of isopropanol and butanol was improved via co-culturing immobilized Clostridium beijerinckii ATCC 6014 with immobilized C.tyrobutyricum ATCC 25755.The production activity of two strains was enhanced,the production of alcohols was significantly increased due to more acids which could be reutilized as carbon source were produced.7.63 g/L isopropanol and 13.26 g/L butanol were achieved from the immobilized co-culture fermentation using the dilute sulfuric acid treated cassava bagasse hydrolysate as carbon source.The total production,yield,volumetric productivity were 20.89 g/L,0.51 g/g,0.44 g/L/h,respectively.The results further indicate the advantages of immobilized-cell culture and strain co-culture which could significantly improve the productions of isopropanol and butanol,when integrated them together.To overcome the toxicity of the solvents,and recover isopropanol and butanol which existing in fermentation broth at low concentration,the extractive ability of some water insoluble organic solvents for isopropanol and butanol were tested by liquid-liquid extraction.The testing results showed that the mixed extractant of dodecanoic acid(35 %)and oleyl alcohol have high capture ability for alcohols.The distribution coefficients of the mixed extractant for isopropanol and butanol are 3.06 and 5.53,respectively.Integrating the liquid-liquid extraction with the immobilized fermentation using the dodecanoic acid mixed extractant to produce isopropanol and butanol,the highest production,yield,volumetric productivity of the total alcohols were 32.31 g/L,0.53 g/g,0.35 g/L/h.Furthermore,65.92 g/L total solvent was recovered from four continuous fed-batch fermentations by mixed extractant.Therefore,not only the inhibitory effects of solvents were decreased,the utilization of substrate was improved,the production of solvents was increased,the most important is that the mixed extractant can extract and accumulate IB at high concentration for the subsequent purification.The focus of this study was to produce isopropanol and butanol from low-cost biomass,which have done some investigation in the conversion of lignocellulose,exploitation of advanced fermentation process,and recovery method of solvents.And these strategies can be provided as technique reserve for the future,which show great potential in improving the productions of isopropanol and butanol.