This is an RSS newsfeed from BioMed Central It is intended to be used with an RSS reader. For more information about RSS newsfeeds from BioMed Central, visit http://www.biomedcentral.com/info/about/rss/ http://www.biotechnologyforbiofuels.commostviewed/ Most viewed articles in last 30 days from Biotechnology for Biofuels (ISSN 1754-6834) published by BioMed Central On 21st January the UK government's Environmental Audit Committee (EAC) published its report on the inquiry "Are biofuels sustainable?". Their short answer, which has since been echoed by a wave of media coverage and environmental group campaigning, was a resounding "No". The report concludes that the stimulation of biofuels production by the UK government and by the EU is reckless. It urges the UK government to withdraw support for biofuels, and to persuade the EU to do likewise by putting a moratorium on the current 5.75% target for biofuels until more sustainable production processes are developed.This review argues against this conclusion. Globally, the development of an efficient biofuels industry is an environmental and economic imperative and the UK should leverage its capabilities in life sciences, energy and process industries to help meet this challenge. The EU is right to promote 'sustainable' biofuels through the Renewable Energy Directive, provided that sustainability criteria are effectively implemented and consistently applied. http://www.biotechnologyforbiofuels.com/content/1/1/9 Sam Cockerill and Chris Martin Biotechnology for Biofuels 2008, 1:9 Number of accesses: 494 2008-05-01 doi:10.1186/1754-6834-1-9 Biotechnology for Biofuels 1754-6834 1 9 2008-05-01 Background: Lignocellulosic bioethanol technologies exhibit significant capacity for performance improvement across the supply chain through the development of high-yielding energy crops, integrated pretreatment, hydrolysis and fermentation technologies and the application of dedicated ethanol pipelines. The impact of such developments on cost-optimal plant location, scale and process composition within multiple plant infrastructures is poorly understood. A combined production and logistics model has been developed to investigate cost-optimal system configurations for a range of technological, system scale, biomass supply and ethanol demand distribution scenarios specific to European agricultural land and population densities. Results: Ethanol production costs for current technologies decrease significantly from $0.71 to $0.58 per litre with increasing economies of scale, up to a maximum single-plant capacity of 550 x 106 l year-1. The development of high-yielding energy crops and consolidated bio-processing realises significant cost reductions, with production costs ranging from $0.33 to $0.36 per litre. Increased feedstock yields result in systems of eight fully integrated plants operating within a 500 x 500 km2 region, each producing between 1.24 and 2.38 x 109 l year-1 of pure ethanol. A limited potential for distributed processing and centralised purification systems is identified, requiring developments in modular, ambient pretreatment and fermentation technologies and the pipeline transport of pure ethanol. Conclusions: The conceptual and mathematical modelling framework developed provides a valuable tool for the assessment and optimisation of the lignocellulosic bioethanol supply chain. In particular, it can provide insight into the optimal configuration of multiple plant systems. This information is invaluable in ensuring (near-)cost-optimal strategic development within the sector at the regional and national scale. The framework is flexible and can thus accommodate a range of processing tasks, logistical modes, by-product markets and impacting policy constraints. Significant scope for application to real-world case studies through dynamic extensions of the formulation has been identified. http://www.biotechnologyforbiofuels.com/content/1/1/13 Alex J Dunnett, Claire S Adjiman and Nilay Shah Biotechnology for Biofuels 2008, 1:13 Number of accesses: 472 2008-07-28 doi:10.1186/1754-6834-1-13 Biotechnology for Biofuels 1754-6834 1 13 2008-07-28 Simultaneous saccharification and fermentation (SSF) is one process option for production of ethanol from lignocellulose. The principal benefits of performing the enzymatic hydrolysis together with the fermentation, instead of in a separate step after the hydrolysis, are the reduced end-product inhibition of the enzymatic hydrolysis, and the reduced investment costs. The principal drawbacks, on the other hand, are the need to find favorable conditions (e.g. temperature and pH) for both the enzymatic hydrolysis and the fermentation and the difficulty to recycle the fermenting organism and the enzymes. To satisfy the first requirement, the temperature is normally kept below 37°C, whereas the difficulty to recycle the yeast makes it beneficial to operate with a low yeast concentration and at a high solid loading. In this review, we make a brief overview of recent experimental work and development of SSF using lignocellulosic feedstocks. Significant progress has been made with respect to increasing the substrate loading, decreasing the yeast concentration and co-fermentation of both hexoses and pentoses during SSF. Presently, an SSF process for e.g. wheat straw hydrolyzate can be expected to give final ethanol concentrations close to 40 g L-1 with a yield based on total hexoses and pentoses higher than 70%. http://www.biotechnologyforbiofuels.com/content/1/1/7 Kim Olofsson, Magnus Bertilsson and Gunnar Lidén Biotechnology for Biofuels 2008, 1:7 Number of accesses: 395 2008-05-01 doi:10.1186/1754-6834-1-7 Biotechnology for Biofuels 1754-6834 1 7 2008-05-01 The cellulase producing ascomycete, Trichoderma reesei (Hypocrea jecorina), is known to secrete a range of enzymes important for ethanol production from lignocellulosic biomass. It is also widely used for the commercial scale production of industrial enzymes because of its ability to produce high titers of heterologous proteins. During the secretion process, a number of post-translational events can occur, however, that impact protein function and stability. Another ascomycete, Aspergillus niger var. awamori, is also known to produce large quantities of heterologous proteins for industry. In this study, T. reesei Cel7A, a cellobiohydrolase, was expressed in A. niger var. awamori and subjected to detailed biophysical characterization. The purified recombinant enzyme contains six times the amount of N-linked glycan than the enzyme purified from a commercial T. reesei enzyme preparation. The activities of the two enzyme forms were compared using bacterial (microcrystalline) and phosphoric acid swollen (amorphous) cellulose as substrates. This comparison suggested that the increased level of N-glycosylation of the recombinant Cel7A (rCel7A) resulted in reduced activity and increased non-productive binding on cellulose. When treated with the N-glycosidase PNGaseF, the molecular weight of the recombinant enzyme approached that of the commercial enzyme and the activity on cellulose was improved. http://www.biotechnologyforbiofuels.com/content/1/1/10 Tina Jeoh, William Michener, Michael E Himmel, Stephen R Decker and William S Adney Biotechnology for Biofuels 2008, 1:10 Number of accesses: 386 2008-05-01 doi:10.1186/1754-6834-1-10 Biotechnology for Biofuels 1754-6834 1 10 2008-05-01 Background: Pretreatment is an essential step in the enzymatic hydrolysis of biomass and subsequent production of bioethanol. Recent results indicate that only a mild pretreatment is necessary in an industrial, economically feasible system. The Integrated Biomass Utilisation System hydrothermal pretreatment process has previously been shown to be effective in preparing wheat straw for these processes without the application of additional chemicals. In the current work, the effect of the pretreatment on the straw cell-wall matrix and its components are characterised microscopically (atomic force microscopy and scanning electron microscopy) and spectroscopically (attenuated total reflectance Fourier transform infrared spectroscopy) in order to understand this increase in digestibility. Results: The hydrothermal pretreatment does not degrade the fibrillar structure of cellulose but causes profound lignin re-localisation. Results from the current work indicate that wax has been removed and hemicellulose has been partially removed. Similar changes were found in wheat straw pretreated by steam explosion. Conclusion: Results indicate that hydrothermal pretreatment increases the digestibility by increasing the accessibility of the cellulose through a re-localisation of lignin and a partial removal of hemicellulose, rather than by disruption of the cell wall. http://www.biotechnologyforbiofuels.com/content/1/1/5 Jan B Kristensen, Lisbeth G Thygesen, Claus Felby, Henning Jørgensen and Thomas Elder Biotechnology for Biofuels 2008, 1:5 Number of accesses: 331 2008-04-16 doi:10.1186/1754-6834-1-5 Biotechnology for Biofuels 1754-6834 1 5 2008-04-16 Background: Pichia stipitis xylose reductase (Ps-XR) has been used to design Saccharomyces cerevisiae strains that are able to ferment xylose. One example is the industrial S. cerevisiae xylose-consuming strain TMB3400, which was constructed by expression of P. stipitis xylose reductase and xylitol dehydrogenase and overexpression of endogenous xylulose kinase in the industrial S. cerevisiae strain USM21. Results: In this study, we demonstrate that strain TMB3400 not only converts xylose, but also displays higher tolerance to lignocellulosic hydrolysate during anaerobic batch fermentation as well as 3 times higher in vitro HMF and furfural reduction activity than the control strain USM21. Using laboratory strains producing various levels of Ps-XR, we confirm that Ps-XR is able to reduce HMF both in vitro and in vivo. Ps-XR overexpression increases the in vivo HMF conversion rate by approximately 20%, thereby improving yeast tolerance towards HMF. Further purification of Ps-XR shows that HMF is a substrate inhibitor of the enzyme. Conclusion: We demonstrate for the first time that xylose reductase is also able to reduce the furaldehyde compounds that are present in undetoxified lignocellulosic hydrolysates. Possible implications of this newly characterized activity of Ps-XR on lignocellulosic hydrolysate fermentation are discussed. http://www.biotechnologyforbiofuels.com/content/1/1/12 João RM Almeida, Tobias Modig, Anja Röder, Gunnar Lidén and Marie-F Gorwa-Grauslund Biotechnology for Biofuels 2008, 1:12 Number of accesses: 327 2008-06-11 doi:10.1186/1754-6834-1-12 Biotechnology for Biofuels 1754-6834 1 12 2008-06-11 Background: Engineering microorganisms to improve metabolite flux requires detailed knowledge of the concentrations and flux rates of metabolites and metabolic intermediates in vivo. Fluorescence resonance energy transfer sensors represent a promising technology for measuring metabolite levels and corresponding rate changes in live cells. These sensors have been applied successfully in mammalian and plant cells but potentially could also be used to monitor steady-state levels of metabolites in microorganisms using fluorimetric assays. Sensors for hexose and pentose carbohydrates could help in the development of fermentative microorganisms, for example, for biofuels applications. Arabinose is one of the carbohydrates to be monitored during biofuels production from lignocellulose, while maltose is an important degradation product of starch that is relevant for starch-derived biofuels production. Results: An Escherichia coli expression vector compatible with phage λ recombination technology was constructed to facilitate sensor construction and was used to generate a novel fluorescence resonance energy transfer sensor for arabinose. In parallel, a strategy for improving the sensor signal was applied to construct an improved maltose sensor. Both sensors were expressed in the cytosol of E. coli and sugar accumulation was monitored using a simple fluorimetric assay of E. coli cultures in microtiter plates. In the case of both nanosensors, the addition of the respective ligand led to concentration-dependent fluorescence resonance energy transfer responses allowing quantitative analysis of the intracellular sugar levels at given extracellular supply levels as well as accumulation rates. Conclusion: The nanosensor destination vector combined with the optimization strategy for sensor responses should help to accelerate the development of metabolite sensors. The new carbohydrate fluorescence resonance energy transfer sensors can be used for in vivo monitoring of sugar levels in prokaryotes, demonstrating the potential of such sensors as reporter tools in the development of metabolically engineered microbial strains or for real-time monitoring of intracellular metabolite during fermentation. http://www.biotechnologyforbiofuels.com/content/1/1/11 Thijs Kaper, Ida Lager, Loren L Looger, Diane Chermak and Wolf B Frommer Biotechnology for Biofuels 2008, 1:11 Number of accesses: 326 2008-06-03 doi:10.1186/1754-6834-1-11 Biotechnology for Biofuels 1754-6834 1 11 2008-06-03 IntroductionThe limited availability of fossil fuel sources, worldwide rising energy demands and anticipated climate changes attributed to an increase of greenhouse gasses are important driving forces for finding alternative energy sources. One approach to meeting the increasing energy demands and reduction of greenhouse gas emissions is by large-scale substitution of petrochemically derived transport fuels by the use of carbon dioxide-neutral biofuels, such as ethanol derived from lignocellulosic material. Results: This paper describes an integrated pilot-scale process where lime-treated wheat straw with a high dry-matter content (around 35% by weight) is converted to ethanol via simultaneous saccharification and fermentation by commercial hydrolytic enzymes and bakers' yeast (Saccharomyces cerevisiae). After 53 hours of incubation, an ethanol concentration of 21.4 g/liter was detected, corresponding to a 48% glucan-to-ethanol conversion of the theoretical maximum. The xylan fraction remained mostly in the soluble oligomeric form (52%) in the fermentation broth, probably due to the inability of this yeast to convert pentoses. A preliminary assessment of the distilled ethanol quality showed that it meets transportation ethanol fuel specifications. The distillation residue, which contained non-hydrolysable and non-fermentable (in)organic compounds, was divided into a liquid and solid fraction. The liquid fraction served as substrate for the production of biogas (methane), whereas the solid fraction functioned as fuel for thermal conversion (combustion), yielding thermal energy, which can be used for heat and power generation. Conclusions: Based on the achieved experimental values, 16.7 kg of pretreated wheat straw could be converted to 1.7 kg of ethanol, 1.1 kg of methane, 4.1 kg of carbon dioxide, around 3.4 kg of compost and 6.6 kg of lignin-rich residue. The higher heating value of the lignin-rich residue was 13.4 MJ thermal energy per kilogram (dry basis). http://www.biotechnologyforbiofuels.com/content/1/1/14 Ronald HW Maas, Robert R Bakker, Arjen R Boersma, Iemke Bisschops, Jan R Pels, Ed de Jong, Ruud A Weusthuis and Hans Reith Biotechnology for Biofuels 2008, 1:14 Number of accesses: 271 2008-08-12 doi:10.1186/1754-6834-1-14 Biotechnology for Biofuels 1754-6834 1 14 2008-08-12 Ethanol is a biofuel that is used as a replacement for approximately 3% of the fossil-based gasoline consumed in the world today. Most of this biofuel is produced from sugarcane in Brazil and corn in the United States. We present here the rationale for the ethanol program in Brazil, its present 'status' and its perspectives. The environmental benefits of the program, particularly the contribution of ethanol to reducing the emission of greenhouse gases, are discussed, as well as the limitations to its expansion. http://www.biotechnologyforbiofuels.com/content/1/1/6 José Goldemberg Biotechnology for Biofuels 2008, 1:6 Number of accesses: 224 2008-05-01 doi:10.1186/1754-6834-1-6 Biotechnology for Biofuels 1754-6834 1 6 2008-05-01 We are pleased to announce a new open access journal, Biotechnology for Biofuels, published online by BioMed Central. Biotechnology for Biofuels will emphasize the research, and application of biotechnology and synergistic operations to improve plant and biological conversion systems for the production of fuels from lignocellulosic biomass and any related economic, environmental and policy issues. That there is a need for this journal is evident: the recent explosion in research on the production and subsequent use of biofuels has huge implications for science and future policy directions, yet Biotechnology for Biofuels is the first open access journal featuring research dedicated to this exciting and expanding field, thereby filling a vacant niche. We are convinced that a free flow of communication will facilitate scientific progress in this hugely important area, and will also help to promote informed public debate. Biotechnology for Biofuels will ensure public availability of high-calibre peer-reviewed research, reviews and commentaries on all aspects of biofuels research and any related political, economic, and environmental issues The benefits of publishing in an open access journal are manifold: open access enables free and universal access to articles online, at no cost to the reader, allowing research to be disseminated by as wide an audience as possible. Submitted manuscripts undergo rapid peer review by internationally renowned experts, drawn in part from our Editorial Board. Articles are published immediately upon acceptance; the communication of research is therefore not postponed until the collation of an 'issue'. The interdisciplinary nature of biofuels research makes the benefits of open access particularly attractive, as it ensures that biologists, chemists, engineers, genomicists and biotechnologists (to name just some of those involved) all have shared access to the latest biofuels research in each of these areas. In this special Editorial, which marks the launch of Biotechnology for Biofuels, the progress and future challenges facing the biofuels field are discussed. http://www.biotechnologyforbiofuels.com/content/1/1/1 Bärbel Hahn-Hägerdal, Michael E Himmel, Chris Somerville and Charles Wyman Biotechnology for Biofuels 2008, 1:1 Number of accesses: 223 2008-04-15 doi:10.1186/1754-6834-1-1 Biotechnology for Biofuels 1754-6834 1 1 2008-04-15