Bioethanol production from biomass: carbohydrate vs syngas fermentation

Environmental problems associated with the use of fossil fuels as well as their expected scarcity in the near future requires a search for new alternative fuels produced from renewable sources. Bioethanol is a biofuel that can be obtained from biomass and waste as feedstocks through fermentation. Two major routes allow conversion of the feedstocks to fermentable substrates, i.e. the hydrolytic route and the thermochemical route. In the hydrolytic route, the feedstock undergoes a pretreatment stage first, aimed at facilitating the subsequent hydrolytic treatment. Chemical, physical or biological pretreatments can be applied. Lignocellulosic feedstocks are mainly composed of cellulose, hemicellulose and lignin. The pretreatment attacks the lignin and hemicellulose polymers and makes cellulose more accessible in the next, hydrolytic, stage. The hydrolytic treatment uses enzymes to convert the cellulose polymer to simple, fermentable, sugars, mainly glucose. Simple sugars obtained from hemicellulose and cellulose are then fermented by yeasts to bioethanol. In the thermochemical alternative, the feedstock is gasified, yielding syngas – a mixture largely composed of CO, CO₂ and H₂ – which can be fermented anaerobically, usually by clostridia, to ethanol or other products. In both cases, downstream processes are then applied to recover and purify the biofuel. The different stages involved in both alternatives are described, and both processes are compared in terms of their main characteristics and development stage. © 2015 Society of Chemical Industry     

Prediction of optimized pretreatment process parameters for biodiesel production using ANN and GA

An artificial neural network (ANN) based program coupled with genetic algorithm (GA) was developed on MATLAB platform for predicting the optimized process parameters required for reducing high free fatty acids (FFA) of any vegetable oils for successful transesterification. The developed ANN was a feed forward back propagation network (4-7-13-1) with one input, two hidden and one output layers. The input parameters for the ANN to generalize the pretreatment process were initial acid value of vegetable oil (IAV), methanol-to-oil ratio (M), catalyst concentration (C) and reaction time (T) and the output parameter was final acid value (FAV) of oil. The developed ANN was trained with the experimental data obtained for jatropha, mahua, simaruoba and rice bran oils with acid value more than 14 mg KOH/g-oil. The trained ANN was tested with separate set of data generated from pretreatment of mahua oil using response surface methodology (RSM) based on central composite rotatable design (CCRD) and found to predict the input pretreatment process parameters with low mean square error (MSE) and relative percent deviation (RPD). The well trained ANN synaptic joint weights and threshold values were used by GA to evaluate the fitness (to get FAV of oil less than 2 after pretreatment) of individuals (combinations of M, C and T) for optimization. The optimized process parameters predicted by the developed ANN-GA technique for sunflower oil with IAV 28 ± 1 mg KOH/g-oil were experimentally verified and the FAV was measured to be 2 ± 0.2 mg KOH/g-oil against the predicted value of 2 mg KOH/g-oil.     

Bioethanol production from rice hull and evaluation of the final solid residue

The objective of this research was to produce bioethanol from rice hulls and to evaluate the recovery and potential use of the residue resulting from the enzymatic hydrolysis step before fermentation. Acid pretreatment and enzymatic hydrolysis were studied for saccharification of polysaccharides. Fermentation was conducted for up to 24?h with Saccharomyces cerevisiae yeast. After process optimization, it was possible to produce >7.0?mg?mL^?1 of ethanol after only 2?h of reaction. Characterization of the solid residues from the hydrolyzed rice husk and the in natura rice husk showed that these solids have different characteristics and present different adsorption potentials because the residue has higher silica content. The product has potential use in industrial or laboratorial adsorption processes. The results from this study offer support for the potential use of rice husks for bioethanol generation and use the solid residue from hydrolysis for adsorption.     

Wet oxidation pretreatment of lignocellulosic residues of sugarcane,rice, cassava and peanuts for ethanol production

Wet oxidation (WO) pretreatment of sugarcane bagasse, rice hulls, cassava stalks and peanut shells was investigated. WO was performed at 195 °C for 10 min, with 2 g kg^?1 of Na₂CO₃ and under either 3 or 12 bar of oxygen. Oxygen pressure and the type of raw material used had a major effect on the fractionation of the materials, formation of sugars and by‐products, and cellulose enzymatic convertibility. Cellulose content in the solid fraction increased after pretreatment of all materials, except rice hulls. The greatest increase, from 361 g kg^?1 to almost 600 g kg^?1, occurred for bagasse. The solubilisation of individual components was different for each material. Bagasse xylan was solubilised to a large extent, and 45.2% of it was recovered as xylose and xylo‐oligosaccharides in the liquid fraction. In the prehydrolysates of rice hulls around 40% of the original glucan was recovered as gluco‐oligosaccharides, due to hydrolysis of starch contained in grain remains. The formation of by‐products was modest for all the materials, but increased with increasing oxygen pressure. The highest yield of acetic acid (34–36 g kg^?1 of raw material) and furfural (0.7–1.8 g kg^?1) occurred for bagasse. The pretreatment enhanced the enzymatic convertibility of cellulose giving the best result (670.2 g kg^?1) for bagasse pretreated at the highest oxygen pressure. However, for the other materials the pretreatment conditions were not effective in achieving cellulose conversions above 450 g kg^?1. Some enzymatic conversion of xylan was observed. Copyright © 2007 Society of Chemical Industry     

Bioethanol production from bio‐ organosolv pulps of Pinus radiata and Acacia dealbata

Wood chips from Pinus radiata and Acacia dealbata were pretreated with the white‐rot fungi Ceriporiopsis subvermispora and Ganoderma australe, respectively, for 30 days at 27 °C and 55% relative humidity, followed by an organosolv delignification with 60% ethanol solution at 200 °C for 1 h to produce pulps with high cellulose and low lignin content. Biotreatment for 30 days was chosen based on low weight and cellulose losses (lower than 4%) and lignin degradation higher than 9%. After organosolv delignification, pulp yield for P. radiata and A. dealbata pulps was 45–49% and 31–51%, respectively. P. radiata bio‐pulps showed higher glucan (93%) and lower lignin content (6%) than control pulps (82% glucan and 13% lignin). A. dealbata bio‐pulps also showed higher glucan (95%) and lower lignin content (2%) than control pulps (92% glucan and 4% lignin). Pulp suspensions at 2% consistency were submitted either to separate enzymatic hydrolysis and fermentation (SHF) or simultaneous enzymatic saccharification and fermentation (SSF) for bioethanol production. The yeast Saccharomyces cerevisiae was used for fermentation. Glucan‐to‐glucose conversion in the enzymatic hydrolysis of control and bio‐pulps of P. radiata was 55% and 100%, respectively, and it was 100% for all pulp samples case of A. dealbata. The highest ethanol yield (calculated as percentage of theoretical yield) during SHF of P. radiata control and bio‐pulps was 38% and 55%, respectively, and for A. dealbata control and bio‐pulps 62% and 69%, respectively. The SSF of P. radiata control and bio‐pulps yielded 10% and 65% of ethanol, respectively, and 77% and 82% for A. dealbata control and bio‐pulps, respectively. In wood basis, the maximum conversion obtained (g ethanol per kg wood) in SHF was 37% and 51% (for P. radiata and A. dealbata pulps, respectively) and 44% and 65% in SSF (for P. radiata and A. dealbata pulps, respectively) regarding the theoretical yield. The low wood‐to‐ethanol conversion was associated with low pulp yield (A. dealbata pulps), high residual lignin amount (P. radiata pulps) and the low pulp consistency (2%) used for SHF and SSF. Copyright © 2007 Society of Chemical Industry     

Bioethanol production from micro-algae, Schizocytrium sp., using hydrothermal treatment and biological conversion

Hydrothermal fractionation for micro-algae, Schizocytrium sp., was investigated to separate sugars, lipids, and proteins. This fractionation process produced protein-rich solid cake and liquid hydrolysates, which contained oligomeric sugars and lipids. Oligomeric sugars and lipids were easily separated by liquid-liquid separation. Sugars in the separated hydrolyzate were determined to be mainly D-glucose and L-galactose. Fractionation conditions were optimized by response surface methodology (RSM). Optimal conditions were found to be 115.5 °C of reaction temperature, 46.7 min of reaction time, and 25% (w/w) of solid loading. The model predicted that maximum oligomeric sugar yield (based on untreated micro-algae weight), which can be recovered by hydrothermal fractionation at the optimum conditions, was 19.4 wt% (based on the total biomass weight). Experimental results were in agreement with the model prediction of 16.6 wt%. Production of bioethanol using micro-algae-induced glucan and E. coli KO11 was tested with SSF (simultaneous saccharification and fermentation), which resulted in 11.8 g-ethanol/l was produced from 25.7 g/l of glucose; i.e. the theoretical maximum ethanol yield based on glucan in hydrolyzate was 89.8%.     

Dynamic models for the production of glucose syrups from cassava starch

This paper presents two dynamic models for the production of glucose syrups from cassava starch. The models used are based on those proposed by Paolucci et al. [Paolucci, D., Belleville, M.P., Zakhia, N. and Rios G.M., 2000a, Kinetics of cassava starch hydrolysis with Termamyl enzyme, Biotechnol Bioeng, 68(1): 71–77; Paolucci, D., Belleville, M.P., Rios, G.M. and Zakhia, N., 2000b, Kinetics of continuous starch hydrolysis in a membrane reactor, Biochem Eng J, 6(3): 233–238] for the liquefaction stage, and Zanin and Moraes [Zanin, G.M. and Moraes, F.F., 1996, Modelling cassava starch saccharification with amyloglucosidase, Appl Biochem Biotechnol 57–58: 617–625] for the saccharification stage. These models were modified in order to include aspects that were not considered in previously reported studies. Hence, the liquefaction stage can be modeled at different operating temperatures and substrate concentrations; furthermore, this model relates the activity of the enzyme with the temperature. This model of the saccharification stage simulates continuous operation at variable operating temperatures. Additionally, it enables the prediction of reduced glucose production due to the inclusion of a thermal deactivation constant. The improvements to each stage of the models permit a better approximation to real behavior by linking the two models to provide a complete simulation of the process.     

氯硝柳胺生产废水的预处理研究

针对氯硝柳胺生产废水中高COD及超高浓度总磷,采用酸析、铁炭微电解、Fenton氧化和钙法沉淀处理技术进行预处理。研究表明,通过对除磷沉淀剂的选择、p H以及加药量等关键因素的控制,可做到废水经过预处理后,COD去除率达88%,除磷率达99.8%,有效降低了废水中COD和总磷浓度,出水达到生化处理进水要求。     

纤维素乙醇的研究进展

近年来以纤维素类生物质为原料制备乙醇的研究取得了许多进展,使纤维素乙醇的开发更具商业化前景.重点介绍了木质纤维素转化为乙醇的原料预处理方法、纤维素和半纤维素的酶法降解、有效可靠的发酵菌种的选育及木质纤维素乙醇制备工艺的开发.     

Bioethanol production by inherent enzymes from rye and wheat with addition of organic farming cheese whey

In organic farming, there is a strong effort to minimize the share of non-renewable resources (e.g. fossil fuels) and use only (preferably on-farm produced) bio-based energy and renewable raw materials, with the aim of achieving sustainable production systems and to become self-sufficient in energy.Throughout our studies, wheat and rye grain was used as raw material in bioethanol production with the purpose of producing in situ enzymes (during germination) for the hydrolysis of starch in the grains and compared with commercial amylase enzyme preparations. Whey permeate was incorporated into the grain in Simultaneous Saccharification and Fermentation (SSF) process to use a cheap nutrient and water source. The ethanol fermentations were completed by 190 h. The fermentation efficiency of germinated and un-germinated grains (without commercial enzymes) was compared with that of commercial enzymes in SSF and furthermore Autoamylolytical Quotient (AAQ) was calculated. On rye 72% yield of the theoretical was achieved by applying commercial enzymes, which decreased only by 10%, when in situ enzymes produced during germination were used alone. The obtained ethanol yields and high (90%) AAQ values showed that rye is a suitable substrate for autoamylolytical processes. According to the low yields (<56%) and AAQs values for all examined wheat samples the results implied that the tested sorts of wheat grains were no efficient for use in autoamylolytical processes.     

调色──着色油漆的最佳化生产

An introduction to the effective tinting method to be used in the paint manufacture.     

High efficiency bioethanol production from OPEFB using pilot pretreatment reactor

BACKGROUND: 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 while avoiding the ethical concerns associated with using potential food resources. RESULTS: Oil palm empty fruit bunches (OPEFB), a lignocellulosic biomass, was pretreated using NaOH to produce bioethanol. The pretreatment and enzymatic hydrolysis conditions were evaluated by response surface methodology (RSM). The optimal conditions were found to be 127.64 °C, 22.08 min, and 2.89 mol L^?1 for temperature, reaction time, and NaOH concentration, respectively. Regarding enzymatic digestibility, 50 FPU g^?1 cellulose of cellulase was selected as the test concentration, resulting in a total glucose conversion rate (TGCR) of 86.37% using the Changhae Ethanol Multi Explosion (CHEMEX) facility. Fermentation of pretreated OPEFB using Saccharomyces cerevisiae resulted in an ethanol concentration of 48.54 g L^?1 at 20% (w/v) pretreated biomass loading, along with simultaneous saccharification and fermentation (SSF) processes. Overall, 410.48 g of ethanol were produced from 3 kg of raw OPEFB in a single run, using the CHEMEX_50 L reactor. CONCLUSION: The results presented here constitute a significant contribution to the production of bioethanol from OPEFB. Copyright © 2011 Society of Chemical Industry     

不同原料生产乙醇的技术发展趋势

论述了糖质原料、淀粉质原料和纤维质原料生产乙醇的主要技术环节,以及这三类原料发酵生产乙醇技术的研究趋势。从充分认识生物质加工过程复杂性的角度,对比分析了糖质原料、淀粉质原料和纤维质原料转化为可发酵糖、可发酵糖发酵生产乙醇的过程特征和相应技术指标。探讨了这三类原料生产燃料乙醇过程中关键技术,包括原料预处理技术、水解技术、发酵技术、副产物利用技术的发展趋势。     

Optimization of pretreatment reaction for methyl ester production from chicken fat

In biodiesel production, to use low cost feedstock such as rendered animal fats may reduce the biodiesel cost. One of the low cost animal fats is the chicken fat for biodiesel production. It is extracted from feather meal which is prepared from chicken wastes such as chicken feathers, blood, offal and trims after rendering process. However, chicken fats often contain significant amounts of FFA which cannot be converted to biodiesel using an alkaline catalyst due to the formation of soap. Therefore, the FFA level should be reduced to desired level (below 1%) by using acid catalyst before transesterification. For this aim, sulfuric, hydrochloric and sulfamic (amidosulfonic) acids were used for pretreatment reactions and the variables affecting the FFA level including alcohol molar ratio, acid catalyst amount and reaction time were investigated by using the chicken fat with 13.45% FFA. The optimum pretreatment condition was found to be 20% sulfuric acid and 40:1 methanol molar ratio based on the amount of FFA in the chicken fat for 80 min at 60 °C. After transesterification, the methyl ester yield was 87.4% and the measured fuel properties of the chicken fat methyl ester met EN 14214 and ASTM D6751 biodiesel specifications.     

萃取置换法预处理氟苯生产废水的实验研究

以磷酸三丁酯(TBP)为萃取剂、NaOH水溶液为反萃剂,采用萃取置换法回收处理氟苯生产废水中的苯酚。研究了萃取剂浓度、萃取时间、pH值及相比对萃取率的影响和相比、反萃时间及NaOH溶液浓度对反萃率的影响。经3级萃取和2级反萃,苯酚的回收率达98%,废水中苯酚含量可降至19.7 mg/L。萃取置换法操作简单,费用低廉,易于工业化。     

Bioethanol production from renewable polymer lichenan using lichenase from an alkalothermophilic Thermomonospora sp. and thermotolerant yeast

Biomass feedstocks available decentrally will be more commodious for localized biorefinery approach than the exhaustive large scale and centralized plants driven by cost intensive technology. Lichen is present in a wide range of habitats in a distributed manner. A maximum hydrolysis of 73%-76% for lichenan from Cetraria islandica, Usnea barbata and Parmelia sp. were obtained in 24 h using lichenase from an alkalothermophilic Thermomonospora sp. wherein the hydrolysis was 100% with commercial enzyme Accellerase™1000. The synergistic role of β-glucosidase in lichenan hydrolysis was demonstrated by the exogenous addition of β-glucosidase to Thermomonospora lichenase which resulted in complete hydrolysis. The hydrolysates of lichenan obtained using Accellerase or a cocktail of Thermomonospora lichenase and β-glucosidase when fermented with free cells of Saccharomyces at 40 °C produced an ethanol yield of 0.45 g/g-0.48 g/g with theoretical conversion efficiencies of 93%-96%. The Ca-alginate immobilized yeast cells were reused eight times at 40 °C with 100% fermentation efficiency.     

Optimization and modeling of biohydrogen production by mixed bacterial cultures from raw cassava starch

The production of bio-hydrogen from raw cassava starch via a mixed-culture dark fermentation process was investigated. The production yield of H₂ was optimized by adjusting the substrate concentration and the microorganism mixture ratio. A maximum H₂ yield of 1.72 mol H₂/mol glucose was obtained with a cassava starch concentration of 10 g/L to give a 90% utilization rate. The kinetics of the substrate utilization and of the generation of both hydrogen and volatile fatty acids were also investigated. The substrate utilization follows pseudo first order reaction kinetics, whereas the production of both H₂ and the VFAs correlate with the Gompertz equation. These results show that cassava is a good candidate for the production of biohydrogen.

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玉米秸秆生物法制取酒精的中间试验

建立了玉米秸秆采用蒸汽爆破预处理、纤维素酶水解和戊糖己糖同步发酵技术制取酒精的中间试验装置。玉米秸秆在1.6～2.0 MPa条件下蒸汽爆破预处理,在提高玉米秸秆对纤维素酶可及度的同时,玉米秸秆中纤维素、木聚糖和木质素损失分别为4.08%、40.02%和9.91%。里氏木霉以10%的原料制备纤维素酶,并用于降解剩余的90%的原料,滤纸酶活力和纤维素酶水解得率分别为2.27 FPIU/mL和71.3%。初始还原物浓度为43.65 g/L的水解糖液经树干毕赤酵母发酵16 h,还原物利用率和酒精得率分别为87.17%和0.43 g/g(酒精/消耗的糖)。     

预处理法促进剩余活性污泥生产挥发性脂肪酸

采用不同方法（加热法,加热超声法,碱处理法）对污泥进行预处理,考察污泥水解酸化效果。结果表明：经加热超声法预处理的活性污泥,在温度315℃,机械搅拌转速450rpm的条件下,污泥厌氧水解酸化12h后,挥发性脂肪酸（VFAs）的产量最高可达3035mg/L,其中主要成分为乙酸841mg/L、丙酸194mg/L、丁酸420mg/L、戊酸1579mg/L。