Progress in the development of methods used for the abatement of microbial contaminants in ethanol fermentations: a review

Biofuel research and development roadmap is currently underway in several countries and is expected to pave a way for the establishment of a viable renewable energy sector that can compete with petroleum-based fuels. Ethanol fermentation has garnered increasing attention amongst various stakeholders (industries, governments, and academia) due to its economic and environmental merits. However, microbial contamination continues to be one of the major barriers in ethanologenic processes, resulting in low ethanol yields and thereby translating into economic losses. To this end, technological innovations geared towards effective elimination of microbial contamination are constantly being developed. This review explores and discusses the fermentation conditions that facilitate the growth of undesired microorganisms during ethanol fermentation processes. It highlights the methods that are currently used in biorefineries as well as innovative and advanced biotechnological methods currently being evaluated as viable alternative strategies to control or eliminate microbial contaminants in ethanol fermentations. These methods have the potential to minimize or control the contamination problem and could pave a way for the development of an efficient biofuel sector.

     

Culture,Conflict, and Translocal Communication: Mobile Technology and Politics in Rural West Bengal,India

As media reports of political movements from various locations have shown, mobile technology can be a powerful political instrument. This paper examines how political activists in West Bengal, India use mobile phones for their daily political work. I seek ways to recognize the disruptive and political potential of mobile technology without ignoring its social and cultural rootedness. I illustrate how riots and protests relate to the increase in translocal communication enabled by phones. I also demonstrate how the political use of mobile technology for extra ordinary events is grounded in the social and political processes of ordinary everyday life and draws from the local understanding of politics by emphasizing certain aspects of it. My article confirms the cultural continuity amidst the increase in translocal relationships but it also pinpoints how cultures harbour conflicts and alternative discourses which translocal communication helps to amplify.     

Fermentative butanol production by Clostridia

Butanol is an aliphatic saturated alcohol having the molecular formula of C(4)H(9)OH. Butanol can be used as an intermediate in chemical synthesis and as a solvent for a wide variety of chemical and textile industry applications. Moreover, butanol has been considered as a potential fuel or fuel additive. Biological production of butanol (with acetone and ethanol) was one of the largest industrial fermentation processes early in the 20th century. However, fermentative production of butanol had lost its competitiveness by 1960s due to increasing substrate costs and the advent of more efficient petrochemical processes. Recently, increasing demand for the use of renewable resources as feedstock for the production of chemicals combined with advances in biotechnology through omics, systems biology, metabolic engineering and innovative process developments is generating a renewed interest in fermentative butanol production. This article reviews biotechnological production of butanol by clostridia and some relevant fermentation and downstream processes. The strategies for strain improvement by metabolic engineering and further requirements to make fermentative butanol production a successful industrial process are also discussed.     

Thermophilic,lignocellulolytic bacteria for ethanol production: current state and perspectives

Lignocellulosic biomass contains a variety of carbohydrates, and their conversion into ethanol by fermentation requires an efficient microbial platform to achieve high yield, productivity, and final titer of ethanol. In recent years, growing attention has been devoted to the development of cellulolytic and saccharolytic thermophilic bacteria for lignocellulosic ethanol production because of their unique properties. First of all, thermophilic bacteria possess unique cellulolytic and hemicellulolytic systems and are considered as potential sources of highly active and thermostable enzymes for efficient biomass hydrolysis. Secondly, thermophilic bacteria ferment a broad range of carbohydrates into ethanol, and some of them display potential for ethanologenic fermentation at high yield. Thirdly, the establishment of the genetic tools for thermophilic bacteria has allowed metabolic engineering, in particular with emphasis on improving ethanol yield, and this facilitates their employment for ethanol production. Finally, different processes for second-generation ethanol production based on thermophilic bacteria have been proposed with the aim to achieve cost-competitive processes. However, thermophilic bacteria exhibit an inherent low tolerance to ethanol and inhibitors in the pretreated biomass, and this is at present the greatest barrier to their industrial application. Further improvement of the properties of thermophilic bacteria, together with the optimization production processes, is equally important for achieving a realistic industrial ethanol production.     

The implications of microarray technology for animal use in scientific research

Microarray technology has the potential to affect the number of laboratory animals used, the severity of animal experiments, and the development of non-animal alternatives in several areas scientific research. Microarrays can contain hundreds or thousands of microscopic spots of DNA, immobilised on a solid support, and their use enables global patterns of gene expression to be determined in a single experiment. This technology is being used to improve our understanding of the operation of biological systems during health and disease, and their responses to chemical insults. Although it is impossible to predict with certainty any future trends regarding animal use, microarray technology might not initially reduce animal use, as is often claimed to be the case. The accelerated pace of research as a result of the use of microarrays could increase overall animal use in basic and applied biological research, by increasing the numbers of interesting genes identified for further analysis, and the number of potential targets for drug development. Each new lead will require further evaluation i n studies that could involve animals. In toxicity testing, microarray studies could lead to increases in animal studies, if further confirmatory and other studies are performed. However, before such technology can be used more extensively, several technical problems need to be overcome, and the relevance of the data to biological processes needs to be assessed. Were microarray technology to be used in the manner envisaged by its protagonists, there need to be efforts to increase the likelihood that its application will create new opportunities for reducing, refining and replacing animal use. This comment is a critical assessment of the possible implications of the application of microarray technology on animal experimentation in various research areas, and makes some recommendations for maximising the application of the Three Rs.     

木质纤维素资源生物精炼技术研究进展

开发利用可再生性的木质纤维素资源来生产液体燃料和大宗化学品,对于解决人类发展面临的资源与环境危机具有重要的意义。然而,作为其代表性工艺的纤维素乙醇生产却因为经济上无法过关而迟迟不能真正实现产业化。采用生物精炼技术,充分利用木质纤维素材料中各种组分,生产包括部分高值产品的多种产品,是克服其转化技术产业化经济可行性问题的有效措施。综述了木质纤维素原料生物精炼技术的研究发展现状,着重阐述了玉米芯的生物精炼技术产业化进展,并对木质纤维素的生物精炼前景进行了展望。     

Integrated biorefineries with engineered microbes and high-value co-products for profitable biofuels production

Corn-based fuel ethanol production processes provide several advantages which could be synergistically applied to overcome limitations of biofuel processes based on lignocellulose. These include resources such as equipment, manpower, nutrients, water, and heat. The fact that several demonstration-scale biomass ethanol processes are using corn as a platform supports this viewpoint. This report summarizes the advantages of first-generation corn-based biofuel processes and then describes the technologies, advantages, and limitations of second-generation lignocellulose-based biofuel systems. This is followed by a discussion of the potential benefit of fully integrating first- and second-generation processes. We conclude with an overview of the technology improvements that are needed to enhance the profitability of biofuel production through development of an integrated biorefinery. A key requirement is creation of industrially robust, multifunctional ethanologens that are engineered for maximum ethanol production from mixed sugars. In addition to ethanol, combined biorefineries could also be the source of valuable co-products, such as chemicals and plastics. However, this will require expression systems that produce high-value co-products. Advantages of this approach are that (1) such strains could be used for bioconversion in any part of the combined biorefinery and (2) using one recombinant organism with many additions should simplify the process of obtaining necessary FDA approval for feed products produced by or containing recombinant organisms.     

Novel applications for microbial transglutaminase beyond food processing

Transglutaminase (EC 2.3.2.13) initially attracted interest because of its ability to reconstitute small pieces of meat into a 'steak'. The extremely high cost of transglutaminase of animal origin has hampered its wider application and has initiated efforts to find an enzyme of microbial origin. Since the early 1990s, many microbial transglutaminase-producing strains have been found, and production processes have been optimized. This has resulted in a rapidly increasing number of applications of transglutaminase in the food sector. However, applications of microbial transglutaminase in other sectors have been explored to a much lesser extent. Here, we will present the wider potential of transglutaminases and discuss recent efforts that could contribute to the realization of their potential.     

Optogenetic switches for light-controlled gene expression in yeast

Light is increasingly recognized as an efficient means of controlling diverse biological processes with high spatiotemporal resolution. Optogenetic switches are molecular devices for regulating light-controlled gene expression, protein localization, signal transduction and protein-protein interactions. Such molecular components have been mainly developed through the use of photoreceptors, which upon light stimulation undergo conformational changes passing to an active state. The current repertoires of optogenetic switches include red, blue and UV-B light photoreceptors and have been implemented in a broad spectrum of biological platforms. In this review, we revisit different optogenetic switches that have been used in diverse biological platforms, with emphasis on those used for light-controlled gene expression in the budding yeast Saccharomyces cerevisiae. The implementation of these switches overcomes the use of traditional chemical inducers, allowing precise control of gene expression at lower costs, without leaving chemical traces, and positively impacting the production of high-value metabolites and heterologous proteins. Additionally, we highlight the potential of utilizing this technology beyond laboratory strains, by optimizing it for use in yeasts tamed for industrial processes. Finally, we discuss how fungal photoreceptors could serve as a source of biological parts for the development of novel optogenetic switches with improved characteristics. Although optogenetic tools have had a strong impact on basic research, their use in applied sciences is still undervalued. Therefore, the invitation for the future is to utilize this technology in biotechnological and industrial settings.

     

Technological and economic potential of poly(lactic acid) and lactic acid derivatives

Abstract: Lactic acid has been an intermediate-volume specialty chemical (world production ∼ 40,000 tons/yr) used in a wide range of food processing and industrial applications. Lactic acid has the potential of becoming a very large volume, commodity-chemical intermediate produced from renewable carbohydrates for use as feedstocks for biodegradable polymers, oxygenated chemicals, plant growth regulators, environmentally friendly 'green' solvents, and specialty chemical intermediates. The recent announcements of new development-scale plants for producing lactic acid and polymer intermediates by major U.S. companies, such as Cargill, Ecochem (DuPont/ConAgra), and Archer Daniels Midland, attest to this potential.
In the past, efficient and economical technologies for the recovery and purification of lactic acid from crude fermentation broths and the conversion of lactic acid to the chemical or polymer intermediates had been the key technology impediments and main process cost centers. The development and deployment of novel separations technologies, such as electrodialysis (ED) with bipolar membranes, extractive distillations integrated with fermentation, and chemical conversion, can enable low-cost production with continuous processes in large-scale operations. The use of bipolar ED can virtually eliminate the salt or gypsum waste produced in the current lactic acid processes. Thus, the emerging technologies can use environmentally sound processes to produce environmentally useful products from lactic acid. The process economics of some of these processes and products can also be quite attractive. In this paper, the recent technical advances in lactic and polyactic acid processes are discussed. The economic potential and manufacturing cost estimates of several products and process options are presented. The technical accomplishments at Argonne National Laboratory (ANL) and the future directions of this program at ANL are discussed.     

The non-use and influence of UK Energy Sector Indicators

This paper presents the results from a case study on the role in policymaking of UK Energy Sector Indicators (ESIs), introduced by the government in 2003. The findings show that the ESIs constituted a very minor element within the broader evidence-base used by policymakers, and that this indicator set and its objectives were poorly known even to central players in the sector. The findings of this research provide further evidence for the observation that scientific knowledge (including evaluations, assessments and indicators) seldom play an instrumental role in policymaking, and are more likely to produce indirect, conceptual and political impacts. The analysis provides a number of tentative conclusions concerning such potential indirect impacts that accrue mainly through processes of dialogue and argumentation both during the preparation of the indicators and after their publication as part of the annual reporting by the UK energy department. The ESIs have played various conceptual and political roles, yet the concrete outcomes in terms of policy change remain to be explored. The conclusions highlight the limitations of rationalist notions of direct, instrumental use in the efforts to understand the role of indicators in policymaking. The paper concludes by three tentative propositions concerning the explanations to the absence of instrumental role of the ESIs, which could be usefully explored in future research: the characteristics of the energy sector; the characteristics of the UK policy culture; and the exceptionality of the ESIs in the general evidence-base of UK energy sector.     

Microchannel enzyme reactors and their applications for processing

Microreaction technology is an interdisciplinary field combining science and engineering. It has attracted the attention of researchers from different fields for the past few years, resulting in the development of several microreactors. Enzymes are one of the catalysts used in microreactors: they are useful for substance production in an environmentally friendly way and have high potential for analytical applications. However, few enzymatic processes have been commercialized because of problems with stability and the cost and efficiency of the reactions. Thus, there have been demands for innovation in process engineering, particularly for enzymatic reactions, and microreaction devices can serve as efficient tools for the development of enzyme processes. In this review, we summarize the recent advances of enzyme-immobilized microchannel reactors; fundamental techniques for micro enzyme-reactor design and important applications of this multidisciplinary technology in chemical processing are also included in our topics.     

Enhancement of 2-phenylethanol productivity by Saccharomyces cerevisiae in two-phase fed-batch fermentations using solvent immobilization

The bioconversion of L-phenylalanine to 2-phenylethanol by Saccharomyces cerevisiae in fed-batch experiments has shown that concentrations of 2-phenylethanol of >2.9 g/L have a negative impact on the oxidative capacity of the yeast. Without tight control on ethanol production, and hence on the feed rate, ethanol rapidly accumulates in the culture media, resulting in complete inhibition of cell growth before the maximal 2-phenylethanol concentration of 3.8 g/L, obtained in the absence of ethanol production, could be achieved. This effect was attributed to a cumulative effect of ethanol and 2-phenylethanol, which reduced the tolerance of the cells for these two products. To enhance the productivity of the bioconversion, a novel in situ product recovery strategy, based on the entrapment of an organic solvent (dibutylsebacate) into a polymeric matrix of polyethylene to form a highly absorbent and chemically and mechanically stable composite resin, was developed. Immobilization of the organic solvent successfully prevented phase toxicity of the solvent and allowed for an efficient removal of 2-phenylethanol from the bioreactor without the need for prior cell separation. The use of the composite resin increased the volumetric productivity of 2-phenylethanol by a factor 2 and significantly facilitated downstream processing, because no stable emulsion was formed. The 2-phenylethanol could be backextracted from the composite resin, yielding a concentrated and almost cell-free solution. In comparison to two-phase extractive fermentations with cells immobilized in alginate-reinforced chitosan beads, the use of a composite resin was extremely inexpensive and simple. In addition, the composite resin was found to be insensitive to abrasion and chemically stable, such that sterilization with 2 M NaOH or heat was possible. Finally, the composite resin could be produced on a large scale using commercially available equipment.     

Improving the corn-ethanol industry: studying protein separation techniques to obtain higher value-added product options for distillers grains

Currently in America the biofuel ethanol is primarily being produced by the dry grind technique to obtain the starch contained in the corn grains and subsequently subjected to fermentation. This so-called 1st generation technology has two setbacks; first the lingering debate whether its life cycle contributes to a reduction of fossil fuels and the animal feed sectors future supply/demand imbalance caused by the co-product dry distillers grains (DDGS). Additional utilization of the cellulosic components and separation of the proteins for use as chemical precursors have the potential to alleviate both setbacks. Several different corn feedstock layouts were treated with 2nd generation ammonia fiber expansion (AFEX) pre-treatment technology and tested for protein separation options (protease solubilization). The resulting system has the potential to greatly improve ethanol yields with lower bioprocessing energy costs and satisfy a significant portion of the organic chemical industry.     

The biotech equipment and supplies sector in Europe-is it European?

Socio-economic research on biotechnology is dealing mainly with the sectors of biopharmaceuticals, agro-food or environmental technologies. In contrast, the equipment and supplies sector seems to be largely ignored. This is surprising because this sector provides important input in terms of technology and material for the development of biotechnology in general. Our comparative analysis of the sector in eight countries indicates that there exists no specific science base for the sector and that it is largely neglected by public research funding. Commercial activities are concentrated in countries with a large general science base in biotechnology and strong multinational pharmaceutical or chemical companies. There is a rather broad diversity in the way the sector has developed in the eight countries. Our data support the notion that national peculiarities seem dominant for explaining this picture. We anticipate growing business opportunities for European firms to step into large markets of equipment and supplies for functional genomics and protein analyses where Europe maintains a strong science base.     

Evaluation of continuous ethanol fermentation of dilute-acid corn stover hydrolysate using thermophilic anaerobic bacterium <Emphasis Type="Italic">Thermoanaerobacter</Emphasis> BG1L1

Dilute sulfuric acid pretreated corn stover is potential feedstock of industrial interest for second generation fuel ethanol production. However, the toxicity of corn stover hydrolysate (PCS) has been a challenge for fermentation by recombinant xylose fermenting organisms. In this work, the thermophilic anaerobic bacterial strain Thermoanaerobacter BG1L1 was assessed for its ability to ferment undetoxified PCS hydrolysate in a continuous immobilized reactor system at 70°C. The tested strain showed significant resistance to PCS, and substrate concentrations up to 15% total solids (TS) were fermented yielding ethanol of 0.39–0.42 g/g-sugars consumed. Xylose was nearly completely utilized (89–98%) for PCS up to 10% TS, whereas at 15% TS, xylose conversion was lowered to 67%. The reactor was operated continuously for 135 days, and no contamination was seen without the use of any agent for preventing bacterial infections. This study demonstrated that the use of immobilized thermophilic anaerobic bacteria for continuous ethanol fermentation could be promising in a commercial ethanol process in terms of system stability to process hardiness and reactor contamination. The tested microorganism has considerable potential to be a novel candidate for lignocellulose bioconversion into ethanol.     

基于重组策略的一体化生物加工过程最新进展

木质纤维素材料具有储量丰富、原料成本低及可再生等优点,人们期望其能替代石油作为原料来生产多种燃料和化学品,如生物柴油、生物氢、生物乙醇等,而木质纤维素解聚过程的高成本成为实现这一过程的主要障碍。一体化生物加工过程 (Consolidated bioprocessing,CBP) 是指在不添加任何外源水解酶的情况下,直接将木质纤维素原料一步转化为生物化学品的生物加工过程。通过基因工程,将水解酶的生成、木质纤维素的降解和生物产品的生产等功能集成到一个生物体上。对于CBP,人们通常有两种策略可供选择,即本地策略和重组策略。文中重点介绍了基于重组策略的CBP的原理、两种不同的应对方式、合成生物学及代谢工程对其的贡献以及未来所面临的挑战与展望。     

Efficient pretreatment of lignocellulose in ionic liquids/co-solvent for enzymatic hydrolysis enhancement into fermentable sugars

Ionic liquids (ILs) have been widely used as alternative solvents for biomass pretreatment, however, efficient methods that enable economically use of ILs at large scale have not been established. In this study, a new method in which ILs and polar organic solvents (ILs/co-solvent systems) was proposed for efficient pretreatment of lignocellulosic materials. The combination use of appropriate ILs and organic co-solvents can significantly enhance the solubility of lignocellulose due to the lower viscosity of ILs/co-solvent mixture as compared to those of pure ILs while the hydrogen bond basicity was maintained. In addition, the solubility of lignocellulosic materials in ILs/co-solvent system was found to be correlated with the Kamlet-Taft solvent parameters. Moreover, the use of microwave heating also enhances the efficiency of lignocellulose pretreatment. For example, the microwave-assisted [Emim][OAc]-DMSO (1:1 volume ratio) treated-rice straw could be hydrolyzed at least 22 times faster than that of untreated-rice straw by cellulase from Trichoderma reesei. This enhancement was attributed by several factors including more efficient lignin extraction, less crystalline cellulose and lower residual ILs in treated-rice straw. The produced sugars can be effectively fermented by Pichia stipitis for ethanol production. Moreover, [Emim][OAc]-DMSO mixture could be reused at least 5 times without significantly decrease in effectiveness demonstrated that the use of ILs/co-solvent was potential alternative method for large-scale biomass pretreatment.     

Platform biochemicals for a biorenewable chemical industry

The chemical industry is currently reliant on a historically inexpensive, petroleum-based carbon feedstock that generates a small collection of platform chemicals from which highly efficient chemical conversions lead to the manufacture of a large variety of chemical products. Recently, a number of factors have coalesced to provide the impetus to explore alternative renewable sources of carbon. Here we discuss the potential impact on the chemical industry of shifting from non-renewable carbon sources to renewable carbon sources. This change to the manufacture of chemicals from biological carbon sources will provide an opportunity for the biological research community to contribute fundamental knowledge concerning carbon metabolism and its regulation. We discuss whether fundamental biological research into metabolic processes at a holistic level, made possible by completed genome sequences and integrated with detailed structural understanding of biocatalysts, can change the chemical industry from being dependent on fossil-carbon feedstocks to using biorenewable feedstocks. We illustrate this potential by discussing the prospect of building a platform technology based upon a concept of combinatorial biosynthesis, which would explore the enzymological flexibilities of polyketide biosynthesis.