Simultaneous saccharification and fermentation of sludge‐containing cassava mash for batch and repeated batch production of bioethanol by Saccharomyces cerevisiae CHFY0321

BACKGROUND: The aim of this study was to examine the repeated batch production of bioethanol from sludge‐containing cassava mash as starchy substrate by flocculating yeast to improve volumetric bioethanol productivity and to simplify the process of a pre‐culture system. RESULTS: For the repeated batch production of bioethanol using cassava mash, the optimal recycling volume ratio was found to be 5%. The repeated batch fermentation was completed within 36 h, while the batch fermentation was completed after 42 h. Volumetric productivity, final ethanol concentration, and ethanol yield were attained to 2.15 g L^?1 h^?1, 83.64 g L^?1, and 85.15%, respectively. Although cell accumulation in the repeated batch process is difficult due to the cassava mash, the repeated batch process using Saccharomyces cerevisiae CHFY0321 could exhibited 10‐fold higher initial viable cell number (1.7 × 10⁷ CFU mL^?1) than that of the batch process. CONCLUSION: The liquefied cassava powder was directly used for the repeated batch process without removal of sludge. Repeated batch bioethanol production by simultaneous saccharification and fermentation using self‐flocculating yeast could reduce process costs and accelerate commercial applications. This result was probably due in part to the effect of the initial viable cell density. Copyright © 2008 Society of Chemical Industry     

Bioethanol production from corn meal by simultaneous enzymatic saccharification and fermentation with immobilized cells of Saccharomyces cerevisiae var. ellipsoideus

The simultaneous enzymatic saccharification and fermentation (SSF) of corn meal using immobilized cells of Saccharomycescerevisiae var. ellipsoideus yeast in a batch system was studied. The yeast cells were immobilized in Ca-alginate by electrostatic droplet generation method. The process kinetics was assessed and determined and the effect of addition of various yeast activators (mineral salts: ZnSO₄ · 7H₂O and MgSO₄ · 7H₂O, and vitamins: Ca-pantothenate, biotin and myo-inositol) separately or mixed, was investigated. Taking into account high values of process parameters (such as ethanol concentration, ethanol yield, percentage of the theoretical ethanol yield, volumetric productivity and utilized glucose) and significant energy savings the SSF process was found to be superior compared to the SHF process. Further improvement in ethanol production was accomplished with the addition of mineral salts as yeast activators which contributed to the highest increase in ethanol production. In this case, the ethanol concentration of 10.23% (w/w), percentage of the theoretical ethanol yield of 98.08%, the ethanol yield of 0.55 g/g and the volumetric productivity of 2.13 g/l·h were obtained.     

Bioethanol production from optimized pretreatment of cassava stem

The current ethanol production processes using crops such as corn and sugar cane are well established. However, the utilization of cheaper biomasses such as lignocellulose could make bioethanol more competitive with fossil fuels, without the ethical concerns associated with the use of potential food resources. A cassava stem, a lignocellulosic biomass, was pretreated using dilute acid to produce bioethanol. The pretreatment conditions were evaluated using response surface methodology (RSM). As a result, the optimal conditions were 177 °C, 10 min and 0.14 M for the temperature, reaction time and acid concentration, respectively. The enzymatic digestibility of the pretreated cassava stem was examined at various enzyme loadings (10–40 FPU/g cellulose of cellulase and 30 CbU/g of β-glucosidase). With respect to economic feasibility, 20 FPU/g cellulose of cellulase and 30 CbU/g of β-glucosidase were selected for the test concentration and led to a saccharification yield of 70%. The fermentation of the hydrolyzed cassava stem using Saccharomyces cerevisiae resulted in an ethanol concentration of 7.55 g/L and a theoretical fermentation yield of 89.6%. This study made a significant contribution to the production of bioethanol from a cassava stem. Although the maximum ethanol concentration was low, an economically efficient overall process was carried out to convert a lignocellulosic biomass to bioethanol.     

Bioconversion of corn stover hydrolysate to ethanol by a recombinant yeast strain

Three corn stover hydrolysates, enzymatic hydrolysates prepared from acid and alkaline pretreatments separately and hemicellulosic hydrolysate prepared from acid pretreatment, were evaluated in composition and fermentability. For enzymatic hydrolysate from alkaline pretreatment, ethanol yield on fermentable sugars and fermentation efficiency reached highest among the three hydrolysates; meanwhile, ethanol yield on dry corn stover reached 0.175 g/g, higher than the sum of those of two hydrolysates from acid pretreatment. Fermentation process of the enzymatic hydrolysate from alkaline pretreatment was further investigated using free and immobilized cells of recombinant Saccharomyces cerevisiae ZU-10. Concentrated hydrolysate containing 66.9 g/L glucose and 32.1 g/L xylose was utilized. In the fermentation with free cells, 41.2 g/L ethanol was obtained within 72 h with an ethanol yield on fermentable sugars of 0.416 g/g. Immobilized cells greatly enhanced the ethanol productivity, while the ethanol yield on fermentable sugars of 0.411 g/g could still be reached. Repeated batch fermentation with immobilized cells was further attempted up to six batches. The ethanol yield on fermentable sugars maintained above 0.403 g/g with all glucose and more than 92.83% xylose utilized in each batch. These results demonstrate the feasibility and efficiency of ethanol production from corn stover hydrolysates.     

国内外燃料乙醇生产和应用情况分析

介绍国内外燃料乙醇的生产和应用情况。美国和巴西的燃料乙醇产量占世界总产量69%,其中美国约占33%,2006年美国的使用量为1514万t;巴西约占36%,巴西的产量为1265万t。同时,还简介了欧盟、加拿大、日本、印度和泰国的燃料乙醇的应用情况。2006年我国燃料乙醇的使用量约110万t,截至2006年底,我国燃料乙醇的总产能达163万t/a。按不同的原料介绍了我国燃料乙醇的生产工艺,即玉米、木薯、糖蜜、甜高粱和秸秆等。最后对我国燃料乙醇的发展提出了几点建议。     

Determination of optimal pre-treatment conditions for ethanol production from olive-pruning debris by simultaneous saccharification and fermentation

Ethanol generation from lignocellulose materials provides an alternative energy-production system. This study investigates the effect of pre-treatment conditions: maximum temperature (range 423.15-483.15 K) and sulfuric-acid concentration (interval 0.002-0.059 kmol/m³) on fuel-ethanol production from simultaneous saccharification and fermentation (SSF) of olive-pruning debris by Saccharomyces cerevisiae IR2-9a (a thermal acclimatized microorganism, 313.15 K). The influence of these two variables was determined by using a response-surface methodology. Cellulose percentage in pre-treated solids reached a maximum of 71.6% of the content in raw material at 483.15 K and 0.010 kmol/m³ of acid concentration. The conversion of hemicellulose into monosaccharides and oligosaccharides also was analyzed. After the wash and filtration of solids, a significant quantity of d-glucose was obtained in the liquid fraction. For ethanol generation, the bio-fuel yield (maximum of 9.6 kg from 100 kg olive-pruning debris), and volumetric ethanol productivity (maximum of 0.27 kg/(m³ h)), strongly depended on pre-treatments conditions. According to statistical optimization, the highest ethanol yield (9.9 kg ethanol from 100 kg olive-pruning debris) is achieved at 480.15 K using a catalyst concentration of 0.016 kmol/m³. A maximum overall process yield of 15.3 kg ethanol/100 kg olive-pruning debris may result when taking into account ethanol from SSF and d-glucose present in the pre-hydrolysate, assuming its theoretical conversion (22.8 kg ethanol/100 kg raw material, also considering the total conversion of d-xylose in the filtrate).     

Waste paper sludge as a potential biomass for bio-ethanol production

This review describes the utilization of paper sludge (PS), which is waste from the pulp and paper industry. Its advantages make PS the cellulosic biomass with the most potential for bio-refinery research and applicable for industrial scale. Some of the grain based biofuels and chemicals have already been in commercial operation, including fuel ethanol or biochemical products. Unfortunately, research and application of PS are yet in their infancy and suffer from large scale because of low productivity. Reviewing the many researches that are working at the utilization of PS for bio-refineries could encourage the utilization of PS from laboratory research to be applied in industry. For this reason, PS usage as industrial raw material will be effective in solving the environmental problems caused by PS with clean technology. In addition, its conversion to bio-ethanol could offer an alternative solution to the energy crisis from fossil fuel. Two methods of PS utilization as raw material for bio-ethanol production are introduced. The simultaneous saccharification and fermentation (SSF) using cellulase produced by A. cellulolyticus and thermotolerant S. cerevisiae TJ14 gave ethanol yield 0.208 (g ethanol/g PS organic material) or 0.051 (g ethanol/g PS). One pot bioethanol production as a modified consolidated biomass processing (CBP) technology gave ethanol yield 0.19 (g ethanol/g Solka floc) and is considered to be the practical CBP technology for its minimizing process.     

Economics of cellulosic ethanol production in a thermochemical pathway for softwood, hardwood, corn stover and switchgrass

The economics of producing cellulosic ethanol using loblolly pine, natural mixed hardwood, Eucalyptus, corn stover, and switchgrass as feedstocks was simulated in Aspen Plus using the thermochemical process via indirect gasification and mixed alcohol synthesis developed by NREL. Outputs from the simulation were linked to an economic analysis spreadsheet to estimate NPV, IRR, payback and to run further sensitivity analysis of the different combinations of feedstocks. Results indicate that forest-based feedstocks including loblolly pine, natural hardwood and eucalyptus may present more attractive financial returns when compared to switchgrass and corn stover, mainly due to their composition (%C, %H, %ash) and alcohol yield. Simulated alcohol yields from forest-based feedstock were significantly higher than from switchgrass and corn stover. Simulations run with switchgrass and corn stover, also demonstrated greater sensitivity to changes in ethanol price, alcohol yield, capital investment and biomass costs. Furthermore, moisture content of receiving feedstocks greatly affected the economics of the biorefinery. A difference of − 10% in the moisture content of the receiving feedstock affected the NPV of the simulated project by + 25% (with respect to central NPV of ~$192 million).     

The Chatham demonstration: From design to operation of a 20 m/d membrane-based ethanol dewatering system

Distillation/dehydration represents the largest fraction of the energy used in the production of ethanol. The Siftek™ technology introduced in this paper carries the potential of reducing energy consumption of distillation/dehydration by up to 50% through the single pass removal of water from the water/ethanol stream at the beer column outlet, using a novel membrane process.Siftek™ is a polymeric membrane that can be used to dry ethanol in the vapor phase. The membrane preferentially permeates water over ethanol in a continuous process. Energy reductions are obtained because this membrane is well suited to remove large quantities of water without phase change.The Siftek™ technology has been piloted since August 2006 in a Greenfield Ethanol plant in Tiverton, Ontario, Canada. The Tiverton unit has a capacity of 1 m³/d and has been producing fuel ethanol from a feed containing between 75 and 90 wt.% ethanol in a single stage system.Based on the successful operation of the pilot, it was decided to scale-up the technology. A two-stage membrane system with a capacity of 20 m³/d was built for the Greenfield Ethanol plant in Chatham, Ontario, Canada. The unit is equipped with full-scale commercial membrane modules and is capable of treating a beer-column feed containing 60-70 wt.% ethanol, producing > 99 wt.% fuel-grade ethanol.     

Ethanol production by solid state fermentation of sweet sorghum using thermotolerant yeast strain

Solid state fermentation of chopped sweet sorghum particles to produce ethanol was studied statically using thermotolerant yeast. The influence of various process parameters, such as yeast cell concentration, particle size and moisture content, on the ethanol yield was investigated. Optimal values of these parameters were 4 × 10⁶ cells/g raw sorghum, Dp = 1.5 mm and 75%, respectively. Addition of reducing agent H₂SO₃ into the fermentation medium provided anaerobic condition, and obtained the maximum ethanol yield of 7.9 g ethanol per 100 g fresh stalks or 0.46 g ethanol/g total sugar, which was 91% of the theoretic yield.     

Energy, water and process technologies integration for the simultaneous production of ethanol and food from the entire corn plant

This paper presents simultaneous integration of different technologies such as the traditional dry-grind process to obtain ethanol from grain with the gasification of the corn stover followed by either syngas fermentation or catalytic mixed alcohols synthesis. The optimal integrated process when using the entire corn plant (18 kg/s of grain and 10.8 kg/s of stover) is the one in which the dry-grind technology to process corn grain is integrated with the catalytic path for the corn stover due to the improved integration of energy, requiring only 17 MW of energy, 50 MW of cooling and 1.56 gal/gal of freshwater, for an ethanol production cost of 1.22 $/gal. However, the production cost decreases as we only use stover to produce ethanol, while the grain is used for food due to the lower cost of the stover and the more favorable energy balance of the ethanol production process from gasification.     

Assessments of Class F fly ashes for amelioration of soil acidity and their influence on growth and uptake of Mo and Se by canola

Coal fly ash can be used to ameliorate productivity constraints in agricultural soils, but their efficacy still remains highly variable. To ascertain the capacity of Class F fly ashes to modify pH of acidic soils, and their effects on the yield and uptake of molybdenum (Mo) and selenium (Se) by canola (Brassica napus L.), we applied two acidic and two alkaline Class F ashes at rates equivalent to 0, 12, 36, and 108 Mg/ha to the top layer (0-10 cm) of 100 cm long intact cores of acidic sandy clay and clay loam soils. Only the alkaline ash which had the highest calcium carbonate equivalent (2.43%) increased the pH of the top 10 cm of the sandy clay soil. However, this ash was also highly saline and when applied at ?36 Mg/ha it increased the electrical conductivity in the top soil layer. Increases in soil pH as a result of alkaline ash addition also elevated concentrations of Se in the plant shoot. The ashes with high concentrations of Mo and Se generally increased uptake of these elements in the plant shoot and/or seed. When these ashes were applied at 108 Mg/ha they increased the concentrations of these elements in the treated topsoil.     

Treatment of cassava mill wastewater and production of electricity through microbial fuel cell technology

Cassava mill wastewater has a high organic content and is an important economic product of traditional and rural low technology agro-industry in many parts of the world. This study explores the utilization of agro-industrial wastewater collected from cassava mills as a resource for electricity generation by microbial fuel cells (MFCs). Mixed culture sludge was used to inoculate the bottom chamber of the MFCs whilst cassava mill wastewater was used in the MFCs. Experimental results showed that the MFCs could generate electricity from full-strength cyanide laden wastewater (16000 mg-COD/L, 86 mg/L cyanide) with a maximum power density of 1771 mW/m². The results from this study demonstrate the feasibility of using MFC technology to generate electricity whilst simultaneously treating cyanide laden cassava mill wastewater effectively. Using MFCs for cassava mill wastewater treatment provides an attractive way to reduce the cost of wastewater treatment in addition to generating electricity.     

Energy-saving direct ethanol production from viscosity reduction mash of sweet potato at very high gravity (VHG)

Sweet potato is an important dietary and economic material in China (accounting for 85% of global production in 2005) and Southeast Asia. The limitation of using root and tuber of sweet potato mash at high solids content is attributed to its high viscous nature. The aim of this study was to investigate the influence of different viscosity reduction factors and found optimal parameters via a surface response design. The optimal xylanase enzyme dose, pretreatment time and temperature were 1.56 AGU/g, 87.6 min and 44.1 °C, respectively. Using pretreatment sweet potato mash on the optimized condition, the final viscosity 498.1 cp and ethanol yield of 135.1 g/kg was obtained by Saccharomyces cerevisiae, which was equivalent to 90.7% of the theoretical yield.     

燃料乙醇生产及市场

介绍国内外燃料乙醇生产形势,预测2015年和2020年全球燃料乙醇产量分别达到8 500万t和2亿t.测算我国2015年和2020年燃料乙醇需求量分别为850万t和1 000万t,供需缺口分别为610万t和800万t.     

利用两级UASB消化处理实现木薯燃料乙醇的水循环型生产

Considering limited success in target-hitting discharge from alcohol industry, our attention was directed toward a recycling use of distillery spentwash (DS) in cassava bioethanol production by using a two-stage up-flow anaerobic sludge blanket bioremediation (TS-UASBB). With the TS-UASBB, , COD, N and P in the effluent from the DS degraded significantly and their concentrations were kept at 0.2 g•L1, 2.0 g•L1, 1.0 g•L1 and 15 mg•L1, respectively, in 13 batch processes for water-recycled ethanol fermentation. With the effluent used directly as dilution water, no heat-resistant bacteria were found alive. The thirteen-batch ethanol production individually achieved 10% after 48 h fermentation. The starch utilization ratio and total sugar consumption were 90% and 99.5%, respectively. The novel water-recycled bioethanol production process with ethanol fermentation and TS-UASBB has a considerable potential in other starchy and cellulosic ethanol production.     

Enhanced desulfurizing flotation of high sulfur coal by sonoelectrochemical method

Enhanced desulfurizing flotation of high sulfur coal was investigated using the sonoelectrochemical method. The supporting electrolyte used in this process was calcium hydroxide and the additive was anhydrous ethanol. The effects of treatment conditions on desulfurization were studied by a single-factor method. The conditions include anhydrous ethanol concentration, sonoelectrolytic time, current density, and ultrasound intensity. For the coal sample with a particle size of − 0.076 mm, the optimal experimental conditions achieved for anhydrous ethanol, sonoelectrolytic time, current density, and ultrasound intensity are 2.1 mol/L, 20 min, 15 × 10^− 3 A/cm², and 1.2 W/cm², respectively. Optimal conditions cause a sulfur reduction of up to 75.4%. The raw and treated coals were analyzed by infrared spectroscopy and a chemical method. Pyritic sulfur, organic sulfur, and ash are partially removed. Compared with enhanced flotation by ultrasound or electrochemistry, desulfurizing flotation of high sulfur coal by sonoelectrochemistry is an effective technology.     

Fermentation of wheat and triticale hydrolysates: A comparative study

In bioethanol production four wheat varieties were investigated: NS 40S, Renesansa, Rapsodija and Dragana, as well as four triticale varieties: Oganj, Jutro, Odisej and NST 21/06. The samples were grinded and mixed with water under conditions prescribed for bioethanol processing. Liquefaction of wheat samples was conducted at 65 °C and 60 °C for triticale samples. All the investigated samples were prepared with or without the addition of technical enzymes: thermostable α-amylase (Thermamyl SC) and glucoamylase (SAN Super 360 L). After liquefaction and saccharification, the samples were subjected to fermentation with Saccharomyces cerevisiae (dry active instant yeast). After the fermentation step ended, ethanol content was determined, and autoamylolytical quotient was calculated. The following values of autoamylolytical quotient were obtained: 71.79% for variety NS 40S; 72.22% for variety Dragana; 62.15% for variety Rapsodija and 81.46% for variety Renesansa. The obtained results revealed that Renesansa is the most suitable wheat variety for bioethanol production due to the largest amount of its native amylolytical enzymes. The following autoamylolytical quotients were obtained for triticale: 99.30% for variety Oganj; 98.65% for variety Jutro; 99.55% for variety Odisej and 94.24% for variety NST 21/06. The results implied that, in the case of triticale, technical enzymes were not needed for starch degradation. It is possible to conduct preparation of triticale at 60 °C.     

Continuous biodiesel production using a fixed-bed Lewis-based catalytic system

It was developed a fixed bed tubular continuous reactor to produce biodiesel, using pellets of aluminum oxide doped with zinc oxide. The pellets were placed into a tubular reactor as a 30 cm long column (2.65 kg). The reactor was feed with soybean oil (168 g h⁻¹) and methanol or ethanol (89 g h⁻¹) with the temperature fixed at 100 °C. Under these conditions it was possible to convert soybean oil into biodiesel in up to 75% yield in the case of methanol and 35% for ethanol. Increasing the temperature to 180 °C, it was possible to ethanolise soybean oil with yields up to 78%. It is important to note that after a steady state is achieved the conversions remained approximately constant with time. It is also worth to mention that the fixed bed remained active for more than 120 h, showing no catalyst leaching or deactivation, and so far it was not possible to determine its overall productivity.     

Production of ethyl ester from crude palm oil by two-step reaction with a microwave system

The production of ethyl esters of fatty acids from a feed material of crude palm oil (CPO) with a high free fatty acid (FFA) content under microwave assistance has been investigated. Parametric studies have been carried out to investigate the optimum conditions for the esterification process (amount of ethanol, amount of catalyst, reaction time, and microwave power). As a result, a molar ratio of FFA to ethanol of 1:24 with 4% wt./wt. of H₂SO₄/FFA, a microwave power of 70 W, and a reaction time of 60 min have been identified as optimum reaction parameters for the esterification process aided by microwave heating. At the end of the esterification process, the amount of FFA had been reduced from 7.5 wt.% to less than 2 wt.%. Similar results were obtained following conventional heating at 70 °C, but only after a reaction time of 240 min. Transesterification of the esterified palm oil has been accomplished with a molar ratio of CPO to ethanol of 1:4, 1.5 wt.% KOH as a catalyst, a microwave power of 70 W, and a reaction time of 5 min. This two-step esterification and transesterification process provided a yield of 80 wt.% with an ester content of 97.4 wt.%. The final ethyl ester product met with the specifications stipulated by ASTM D6751-02.