Ionic liquid ethanol sensor

Ionic liquids containing lithium methylsulfonyl group were prepared from the precursors poly(propylene glycol)-block-(ethylene glycol)-block-(propylene glycol)-bis(2-aminopropyl ether) with different molecular weight. These liquids revealed excellent electrical conductivity in the temperature range -25 to 85 degrees C. Also, they exhibited a high boiling temperature and hence a low vapor pressure in ambient condition. Additionally, they showed a high fluidity with their viscosities being comparative with that of water. To determine the sensitivity of an ethanol sensor by using these ionic liquids, these liquids were subjected into a sequential electrochemical tests with nickel electrodes which performed a high sensitivity for the ethanol sensor. It was found that only the derivative with low molecular weight could detect ethanol. Furthermore, a linear relationship between the response current and the concentration of ethanol was constructed. The detection limit was found to be 0.13% (v/v) and its response time was 336 s.     

Studies on cellulosic ethanol production for sustainable supply of liquid fuel in China

As the biggest developing country, China faces a serious challenge in satisfying its need for huge amounts of energy resources, especially for liquid fuel. The Chinese government has recently started a bioethanol project, and has produced about 1 million tons of ethanol fuel from corn and wheat in 2005. As it has the largest population in the world and limited lands for food production, cellulosic ethanol would be a more suitable choice for China. Many research projects in China on biodegradation and biotransformation of lignocellulosics have been carried out. Furthermore, understanding the biodegradation mechanism of lignocellulosics and developing practical processes for ethanol production have been ongoing. After more than 30 years of research, several pilot scale facilities have been set up, and lots of experience has been acquired. However, the calculated production cost of cellulosic ethanol is still higher than that of corn ethanol. To overcome this problem, the biorefinery conception has been introduced into research on lignocellulosics transformation. A corncob biorefinery process has been developed in Shandong University. By combining the cellulase and ethanol production with a xylose-related products production, the total production cost can be reduced. A scale of 50,000-ton/year cellulosic ethanol biorefinery is being planned to be built at Yucheng.     

Advances in ethanol production

Barriers to the commercialization of lignocellulosic ethanol include the development of more robust biocatalysts, reduction of cellulase costs, and high capital cost associated with a complex process. Improvements have been made in all areas during the past two years. Oxidoreductases, transporters, and regulators have been identified that can increase the tolerance of biocatalysts to inhibitors formed during pretreatment. Biocatalysts are being developed that grow under conditions that are optimal for cellulase activity and others have been engineered to produce glycoside hydrolases. Ethanol yields resulting from most current process configurations are similar, approximately 0.21 g ethanol/g dry cellulosic feedstock. Potentially, this can be increased to at least 0.27 g ethanol/g biomass (83 gal/ton) using simpler processes.     

Bacterial contaminants of fuel ethanol production

Bacterial contamination is an ongoing problem for commercial fuel ethanol production facilities. Both chronic and acute infections are of concern, due to the fact that bacteria compete with the ethanol-producing yeast for sugar substrates and micronutrients. Lactic acid levels often rise during bouts of contamination, suggesting that the most common contaminants are lactic acid bacteria. However, quantitative surveys of commercial corn-based fuel ethanol facilities are lacking. For this study, samples were collected from one wet mill and two dry grind fuel ethanol facilities over a 9 month period at strategic time points and locations along the production lines, and bacterial contaminants were isolated and identified. Contamination in the wet mill facility consistently reached 10⁶ bacteria/ml. Titers from dry grind facilities were more variable but often reached 10⁸/ml. Antibiotics were not used in the wet mill operation. One dry grind facility added antibiotic to the yeast propagation tank only, while the second facility dosed the fermentation with antibiotic every 4 h. Neither dosing procedure appeared to reliably reduce overall contamination, although the second facility showed less diversity among contaminants. Lactobacillus species were the most abundant isolates from all three plants, averaging 51, 38, and 77% of total isolates from the wet mill and the first and second dry grind facilities, respectively. Although populations varied over time, individual facilities tended to exhibit characteristic bacterial profiles, suggesting the occurrence of persistent endemic infections.Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

木薯原料生产燃料乙醇

以下介绍了我国木薯原料生产燃料乙醇的最新进展,并对我国的木薯资源分布作了分析,特别强调了木薯资源占全国总产量的65%以上的广西壮族自治区在我国发展木薯原料燃料乙醇过程中所起的重要作用,在此基础上对我国发展木薯原料燃料乙醇所遇到的困难和挑战进行了分析,并根据国内外的科技进展对如何克服这些困难提出了几个可能的解决方案。     

Re-engineering Escherichia coli for ethanol production

A lactate producing derivative of Escherichia coli KO11, strain SZ110, was re-engineered for ethanol production by deleting genes encoding all fermentative routes for NADH and randomly inserting a promoterless mini-Tn5 cassette (transpososome) containing the complete Zymomonas mobilis ethanol pathway (pdc, adhA, and adhB) into the chromosome. By selecting for fermentative growth in mineral salts medium containing xylose, a highly productive strain was isolated in which the ethanol cassette had been integrated behind the rrlE promoter, designated strain LY160 (KO11, Δfrd::celY _Ec ΔadhE ΔldhA, ΔackA lacA::casAB _Ko rrlE::(pdc _Zm -adhA _Zm -adhB _Zm -FRT-rrlE) pflB ⁺ ). This strain fermented 9% (w/v) xylose to 4% (w/v) ethanol in 48 h in mineral salts medium, nearly equal to the performance of KO11 with Luria broth.     

Batch ethanol production with dual organisms

Summary The concept of improving ethanol productivity in batch fermentation by utilising two organisms with different substrate and product inhibition characteristics was examined. The inocula consisted of two yeasts chosen because of their different inhibition properties at high sugar and high ethanol concentrations respectively. Improved productivity was found in the dual system. A numerical analysis which incorporates the non-linear nature of the inhibition demonstrates the level of improvement which might be attained in such systems.     

Aeration alleviates ethanol inhibition and glycerol production during fed-batch ethanol fermentation

In this study, we investigated the effects of aeration on ethanol inhibition and glycerol production during fed-batch ethanol fermentation. When aeration was conducted at 0.13, 0.33, and 0.8 vvm, the ethanol productivity, specific ethanol production rate, and ethanol yield in the presence of greater than 100 g/L of ethanol were higher than when aeration was not conducted. In addition, estimation of the parameters (α and β) in a model equation of ethanol inhibition kinetics indicated that aeration alleviated ethanol inhibition against the specific growth rate and the specific ethanol production rate. Specifically, when aeration was conducted, the glycerol yield and specific glycerol production rate decreased approximately 50 and 70%, respectively. Finally, the results of this study indicated that aeration during fed-batch ethanol fermentation may improve the ethanol concentration in the final culture broth, as well as the ethanol productivity.     

The inhibitory effect of ethanol on ethanol production by Zymomonas mobilis

Summary In an effort to establish the reasons for the limitations in the final ethanol concentration of Zymomonas mobilis fermentation, the effects of CO₂ and ethanol on the fermentation were investigated using continuous and fed-batch cultivation systems. The nucleation and stripping out of CO₂ from the fermenter using diatomaceous earth or nitrogen gas or both exhibited a profound effect on the glucose uptake rate during the early stages of fed-batch fermentation, but did not improve final ethanol yields. The addition of ethanol together with above mentioned experiments confirmed conclusively that ethanol inhibition is responsible for the final ethanol concentration obtainable during Zymomonas mobilis fermentation. The final concentration lies between 90 and 110 gl⁻¹ or approximately 12–15% (v/v) ethanol.     

The ethanol pathway from Thermoanaerobacterium saccharolyticum improves ethanol production in Clostridium thermocellum

Clostridium thermocellum ferments cellulose, is a promising candidate for ethanol production from cellulosic biomass, and has been the focus of studies aimed at improving ethanol yield. Thermoanaerobacterium saccharolyticum ferments hemicellulose, but not cellulose, and has been engineered to produce ethanol at high yield and titer. Recent research has led to the identification of four genes in T. saccharolyticum involved in ethanol production: adhE, nfnA, nfnB and adhA. We introduced these genes into C. thermocellum and observed significant improvements to ethanol yield, titer, and productivity. The four genes alone, however, were insufficient to achieve in C. thermocellum the ethanol yields and titers observed in engineered T. saccharolyticum strains, even when combined with gene deletions targeting hydrogen production. This suggests that other parts of T. saccharolyticum metabolism may also be necessary to reproduce the high ethanol yield and titer phenotype in C. thermocellum.     

Metabolic engineering of bacteria for ethanol production

Technologies are available which will allow the conversion of lignocellulose into fuel ethanol using genetically engineered bacteria. Assembling these into a cost-effective process remains a challenge. Our work has focused primarily on the genetic engineering of enteric bacteria using a portable ethanol production pathway. Genes encoding Zymomonas mobilis pyruvate decarboxylase and alcohol dehydrogenase have been integrated into the chromosome of Escherichia coli B to produce strain KO11 for the fermentation of hemicellulose-derived syrups. This organism can efficiently ferment all hexose and pentose sugars present in the polymers of hemicellulose. Klebsiella oxytoca M5A1 has been genetically engineered in a similar manner to produce strain P2 for ethanol production from cellulose. This organism has the native ability to ferment cellobiose and cellotriose, eliminating the need for one class of cellulase enzymes. The optimal pH for cellulose fermentation with this organism (pH 5.0-5.5) is near that of fungal cellulases. The general approach for the genetic engineering of new biocatalysts has been most successful with enteric bacteria thus far. However, this approach may also prove useful with Gram-positive bacteria which have other important traits for lignocellulose conversion. Many opportunities remain for further improvements in the biomass to ethanol processes. These include the development of enzyme-based systems which eliminate the need for dilute acid hydrolysis or other pretreatments, improvements in existing pretreatments for enzymatic hydrolysis, process improvements to increase the effective use of cellulase and hemicellulase enzymes, improvements in rates of ethanol production, decreased nutrient costs, increases in ethanol concentrations achieved in biomass beers, increased resistance of the biocatalysts to lignocellulosic-derived toxins, etc. To be useful, each of these improvements must result in a decrease in the cost for ethanol production. Copyright 1998 John Wiley & Sons, Inc.     

Continuous tower fermentation for power ethanol production

Summary The capability of the continuous tower fermenter to accumulate and retain high cell densities (70–90 g dry wt/1) when using naturally flocculant yeasts is demonstrated with semi-defined glucose feed at concentrations of 120–200 g/1 and high hydraulic loadings. Conversion and ethanol productivity data are given as a function of throughput and feed glucose concentration.     

产乙醇工程菌研究进展

伴随着21世纪的到来,低油价的时代也悄然落幕。简要概述了燃料乙醇产生菌代谢工程的研究进展,包括了利用淀粉、戊糖及纤维素的工程酵母构建,运动发酵单胞菌利用戊糖工程菌的构建,引入外源乙醇合成途径的大肠埃希氏菌和产酸克雷伯氏菌等。对燃料乙醇的重视将促进开发能利用廉价原料和要求粗放的工程菌株用于高产乙醇的生产过程,以降低成本和能耗,其中能利用生淀粉的工程酵母及利用木质纤维素水解物的运动发酵单胞菌工程菌有较大的工业化潜力。     

Microbial production of ethanol from carbon monoxide

Production of ethanol from fermentation of CO has received much attention in the last few years with several companies proposing to use CO fermentation in their ethanol production processes. The genomes of two CO fermenters, Clostridium ljungdahlii and Clostridium carboxidivorans, have recently been sequenced. The genetic information obtained from this sequencing is aiding molecular biologists who are enhancing ethanol and butanol production by genetic manipulation. Several studies have optimized media for CO fermentation, which has resulted in enhanced ethanol production. Also, new reactor designs involving the use of hollow fiber membranes have reduced mass transfer barriers that have hampered previous CO fermentation efforts.     

Paddy straw as substrate for ethanol production

Pretreatment of paddy straw with 2% sodium hydroxide at 15 psi for 1 h resulted in 83% delignification. The hydrolysis of alkali treated paddy straw with a commercial preparation of cellulase for 2 h at 50°C resulted in release of 65% total reducing sugars. Maximum sugars were released at enzyme loading of 1.5% (v/v). The fermentation of hydrolysate supplemented with nutrients by S. cerevisiae resulted in the production of 20–30 g L⁻¹ ethanol after 48 h incubation which was further improved with addition of yeast nitrogen base and inoculated with 1% (w/v) yeast cells.     

Feasibility of ethanol production from coffee husks

The objective of this work was to evaluate the feasibility of ethanol production by fermentation of coffee husks by Saccharomyces cerevisiae. Batch fermentation studies were performed employing whole and ground coffee husks, and aqueous extract from ground coffee husks. It was observed that fermentation yield decreased with an increase in yeast concentration. The best results were obtained for the following conditions: whole coffee husks, 3 g yeast/l substrate, temperature of 30°C. Under these conditions ethanol production was 8.49 ± 0.29 g/100 g dry basis (13.6 ± 0.5 g ethanol/l), a satisfactory value in comparison to literature data for other residues such as corn stalks, barley straw and hydrolyzed wheat stillage (5–11 g ethanol/l). Such results indicate that coffee husks present excellent potential for residue-based ethanol production.     

Characterization of wine yeasts for ethanol production

Summary Selected wine yeasts were tested for their ethanol and sugar tolerance, and for their fermentative capacity. Growth () and fermentation rates () were increasingly inhibited by increasing ethanol and glucose concentrations, flor yeasts being the least inhibited. Except in the latter strains, the ethanol production rate was accelerated by adding the glucose stepwise. The best fermenting strains selected in laboratory medium were also the best at fermenting molasses. Invertase activity was not a limiting step in ethanol production, being accelerated by supplementing molasses with ammonia and biotine, and by cell recycle.     

Continuous ethanol production by immobilized yeast reactor

Summary Saccharomyces cerevisiae yeast immobilized in calcium alginate gel beads was employed in packed-bed column reactors for continuous ethanol production from glucose or cane molasses, and for beer fermentation from barley malt wort. With properly balanced nutrient content or periodical regeneration of cells by nutrient addition and aeration, ethanol production could be maintained for several months. About 7 percent (w/v) ethanol content could be easily maintained with cane molasses diluted to about 17.5 percent (w/v) of total reducing sugars at about 4 to 5 h residence time. Beer of up to 4.5 percent (wv) of ethanol could be produced from barley wort at about 2 h residence time without any addition of nutrients.