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.com The latest articles from Biotechnology for Biofuels (ISSN 1754-6834) published by BioMed Central 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. Conclusions: 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 Joao R.M. Almeida, Tobias Modig, Anja Roder, Gunnar Liden and Marie F. Gorwa-Grauslund Biotechnology for Biofuels 2008, 1:12 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 lambda 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. Conclusions: 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 2008-06-03 doi:10.1186/1754-6834-1-11 Biotechnology for Biofuels 1754-6834 1 11 2008-06-03 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 2008-05-01 doi:10.1186/1754-6834-1-10 Biotechnology for Biofuels 1754-6834 1 10 2008-05-01 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 2008-05-01 doi:10.1186/1754-6834-1-9 Biotechnology for Biofuels 1754-6834 1 9 2008-05-01 Background: A metabolic regulation study was performed, based upon measurements of enzymatic activities, fermentation performance, and RT-PCR analysis of pathways related to central carbon metabolism, in an ethanologenic Escherichia coli strain (CCE14) derived from lineage C. In comparison with previous engineered strains, this E coli derivative has a higher ethanol production rate in mineral medium, as a result of the elevated heterologous expression of the chromosomally integrated genes encoding PDCZm and ADHZm (pyruvate decarboxylase and alcohol dehydrogenase from Zymomonas mobilis). It is suggested that this behavior might be due to lineage differences between E. coli W and C. Results: This study demonstrated that the glycolytic flux is controlled, in this case, by reactions outside glycolysis, i.e., the fermentative pathways. Changes in ethanol production rate in this ethanologenic strain result in low organic acid production rates, and high glycolytic and ethanologenic fluxes, that correlate with enhanced transcription and enzymatic activity levels of PDCZm and ADHZm. Furthermore, a higher ethanol yield (90% of the theoretical) in glucose-mineral media was obtained with CCE14 in comparison with previous engineered E. coli strains, such as KO11, that produces a 70% yield under the same conditions. Conclusion: Results suggest that a higher ethanol formation rate, caused by ahigher PDCZm and ADHZm activities induces a metabolic state that cells compensate through enhanced glucose transport, ATP synthesis, and NAD-NADH+H turnover rates. These results show that glycolytic enzymatic activities, present in E. coli W and C under fermentative conditions, are sufficient to contend with increases in glucose consumption and product formation rates. http://www.biotechnologyforbiofuels.com/content/1/1/8 Montserrat Orencio-Trejo, Noemí Flores, Adelfo Escalante, Georgina Hernández-Chávez, Francisco Bolívar, Guillermo Gosset and Alfredo Martinez Biotechnology for Biofuels 2008, 1:8 2008-05-01 doi:10.1186/1754-6834-1-8 Biotechnology for Biofuels 1754-6834 1 8 2008-05-01 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 2008-05-01 doi:10.1186/1754-6834-1-7 Biotechnology for Biofuels 1754-6834 1 7 2008-05-01 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 2008-05-01 doi:10.1186/1754-6834-1-6 Biotechnology for Biofuels 1754-6834 1 6 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 2008-04-16 doi:10.1186/1754-6834-1-5 Biotechnology for Biofuels 1754-6834 1 5 2008-04-16 Background: There is currently a steady increase in the use of wood-based fuels for heat and power production in Sweden. A major proportion of these fuels could serve as feedstock for ethanol production. In this study various options for the utilization of the solid residue formed during ethanol production from spruce, such as the production of pellets, electricity and heat for district heating, were compared in terms of overall energy efficiency and production cost. The effects of changes in the process performance, such as variations in the ethanol yield and/or the energy demand, were also studied. The process was based on SO2-catalysed steam pretreatment, which was followed by simultaneous saccharification and fermentation. A model including all the major process steps was implemented in the commercial flow-sheeting program Aspen Plus, the model input was based on data recently obtained on lab scale or in a process development unit. Results: For the five base case scenarios presented in the paper the overall energy efficiency ranged from 53 to 92%, based on the lower heating values, and a minimum ethanol selling price from 3.87 to 4.73 Swedish kronor per litre (0.41–0.50 EUR/L); however, ethanol production was performed in essentially the same way in each base case scenario. (Highly realistic) improvements in the ethanol yield and reductions in the energy demand resulted in significantly lower production costs for all scenarios. Conclusion: Although ethanol was shown to be the main product, i.e. yielding the major part of the income, the co-product revenue had a considerable effect on the process economics and the importance of good utilization of the entire feedstock was clearly shown. With the assumed prices of the co-products, utilization of the excess solid residue for heat and power production was highly economically favourable. The study also showed that improvements in the ethanol yield and reductions in the energy demand resulted in significant production cost reductions almost independently of each other. http://www.biotechnologyforbiofuels.com/content/1/1/4 Per Sassner and Guido Zacchi Biotechnology for Biofuels 2008, 1:4 2008-04-15 doi:10.1186/1754-6834-1-4 Biotechnology for Biofuels 1754-6834 1 4 2008-04-15 Background: Lignocellulosic materials are abundant and among the most important potential sources for bioethanol production. Although the pretreatment of lignocellulose is necessary for efficient saccharification and fermentation, numerous by-products, including furan derivatives, weak acids, and phenolic compounds, are generated in the pretreatment step. Many of these components inhibit the growth and fermentation of yeast. In particular, vanillin is one of the most effective inhibitors in lignocellulose hydrolysates because it inhibits fermentation at very low concentrations. To identify the genes required for tolerance to vanillin, we screened a set of diploid yeast deletion mutants, which are powerful tools for clarifying the function of particular genes. Results: Seventy-six deletion mutants were identified as vanillin-sensitive mutants. The numerous deleted genes in the vanillin-sensitive mutants were classified under the functional categories for 'chromatin remodeling' and 'vesicle transport', suggesting that these functions are important for vanillin tolerance. The cross-sensitivity of the vanillin-sensitive mutants to furan derivatives, weak acids, and phenolic compounds was also examined. Genes for ergosterol biosynthesis were required for tolerance to all inhibitory compounds tested, suggesting that ergosterol is a key component of tolerance to various inhibitors. Conclusion: Our analysis predicts that vanillin tolerance in Saccharomyces cerevisiae is affected by various complicated processes that take place on both the molecular and the cellular level. In addition, the ergosterol biosynthetic process is important for achieving a tolerance to various inhibitors. Our findings provide a biotechnological basis for the molecular engineering as well as for screening of more robust yeast strains that may potentially be useful in bioethanol fermentation. http://www.biotechnologyforbiofuels.com/content/1/1/3 Ayako Endo, Toshihide Nakamura, Akira Ando, Ken Tokuyasu and Jun Shima Biotechnology for Biofuels 2008, 1:3 2008-04-15 doi:10.1186/1754-6834-1-3 Biotechnology for Biofuels 1754-6834 1 3 2008-04-15 Background: Lignocellulosic biomass such as wood is an attractive material for fuel ethanol production. Pretreatment technologies that increase the digestibility of cellulose and hemicellulose in the lignocellulosic biomass have a major influence on the cost of the subsequent enzymatic hydrolysis and ethanol fermentation processes. Pretreatments without chemicals such as acids, bases or organic solvents are less effective for an enzymatic hydrolysis process than those with chemicals, but they have a less negative effect on the environment. Results: The enzymatic digestibility of eucalyptus was examined following a combined pretreatment without chemicals comprising a ball milling (BM) and hot-compressed water (HCW) treatment. The BM treatment simultaneously improved the digestibility of both glucan and xylan, and was effective in lowering the enzyme loading compared with the HCW treatment. The combination of HCW and BM treatment reduced the BM time. The eucalyptus treated with HCW (160°C, 30 minutes) followed by BM (20 minutes) had an approximately 70% yield of total sugar with a cellulase loading of 4 FPU/g substrate. This yield was comparable to the yields from samples treated with HCW (200°C, 30 minutes) or BM (40 minutes) hydrolyzed with 40 FPU/g substrate. Conclusion: The HCW treatment is useful in improving the milling efficiency. The combined HCW-BM treatment can save energy and enzyme loading. http://www.biotechnologyforbiofuels.com/content/1/1/2 Hiroyuki Inoue, Shinichi Yano, Takashi Endo, Tsuyoshi Sakaki and Shigeki Sawayama Biotechnology for Biofuels 2008, 1:2 2008-04-15 doi:10.1186/1754-6834-1-2 Biotechnology for Biofuels 1754-6834 1 2 2008-04-15 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 2008-04-15 doi:10.1186/1754-6834-1-1 Biotechnology for Biofuels 1754-6834 1 1 2008-04-15