Addressing the Need for Alternative Transportation Fuels: The Joint BioEnergy Institute

Joint BioEnergy Institute, Department of Chemical Engineering, University of California, Berkeley, California 94720, USA.
ACS Chemical Biology (Impact Factor: 5.33). 02/2008; 3(1):17-20. DOI: 10.1021/cb700267s
Source: PubMed


Today, carbon-rich fossil fuels, primarily oil, coal, and natural gas, provide 85% of the energy consumed in the U.S. As world demand increases, oil reserves may become rapidly depleted. Fossil fuel use increases CO emissions and raises the risk of global warming. The high energy content of liquid hydrocarbon fuels makes them the preferred energy source for all modes of transportation. In the U.S. alone, transportation consumes >13.8 million barrels of oil per day and generates 0.5 gigatons of carbon per year. This release of greenhouse gases has spurred research into alternative, nonfossil energy sources. Among the options (nuclear, concentrated solar thermal, geothermal, hydroelectric, wind, solar, and biomass), only biomass has the potential to provide a high-energy-content transportation fuel. Biomass is a renewable resource that can be converted into carbon-neutral transporation fuels. Currently, biofuels such as ethanol are produced largely from grains, but there is a large, untapped resource (estimated at more than a billion tons per year) of plant biomass that could be utilized as a renewable, domestic source of liquid fuels. Well-established processes convert the starch content of the grain into sugars that can be fermented to ethanol. The energy efficiency of starch-based biofuels is however not optimal, while plant cell walls (lignocellulose) represent a huge untapped source of energy. Plant-derived biomass contains cellulose, which is more difficult to convert to sugars; hemicellulose, which contains a diversity of carbohydrates that have to be efficiently degraded by microorganisms to fuels; and lignin, which is recalcitrant to degradation and prevents cost-effective fermentation. The development of cost-effective and energy-efficient processes to transform lignocellulosic biomass into fuels is hampered by significant roadblocks, including the lack of specifically developed energy crops, the difficulty in separating biomass components, low activity of enzymes used to deconstruct biomass, and the inhibitory effect of fuels and processing byproducts on organisms responsible for producing fuels from biomass monomers. The Joint BioEnergy Institute (JBEI) is a U.S. Department of Energy (DOE) Bioenergy Research Center that will address these roadblocks in biofuels production. JBEI draws on the expertise and capabilities of three national laboratories (Lawrence Berkeley National Laboratory (LBNL), Sandia National Laboratories (SNL), and Lawrence Livermore National Laboratory (LLNL)), two leading U.S. universities (University of California campuses at Berkeley (UCB) and Davis (UCD)), and a foundation (Carnegie Institute for Science, Stanford) to develop the scientific and technological base needed to convert the energy stored in lignocellulose into transportation fuels and commodity chemicals. Established scientists from the participating organizations are leading teams of researchers to solve the key scientific problems and develop the tools and infrastructure that will enable other researchers and companies to rapidly develop new biofuels and scale production to meet U.S. transportation needs and to develop and rapidly transition new technologies to the commercial sector. JBEI's biomass-to-biofuels research approach is based in three interrelated scientific divisions and a technologies division. The Feedstocks Division will develop improved plant energy crops to serve as the raw materials for biofuels. The Deconstruction Division will investigate the conversion of this lignocellulosic plant material to sugar and aromatics. The Fuels Synthesis Division will create microbes that can efficiently convert sugar and aromatics into ethanol and other biofuels. JBEI's cross-cutting Technologies Division will develop and optimize a set of enabling technologies including high-throughput, chipbased, and omics platforms; tools for synthetic biology; multi-scale imaging facilities; and integrated data analysis to support and integrate JBEI's scientific program.

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    • "Saccharification of lignocellulosic feedstocks has great potential to provide fermentable sugars for production of renewable and potentially carbon neutral biofuels. Significant efforts are underway to determine cost-effective processes to enzymatically hydrolyze these complex and often recalcitrant materials (Helenius and Aebi, 2001; Lynd et al., 2002; Shallom and Shoham, 2003; Doi and Kosugi, 2004; Blanch et al., 2008; Dashtban et al., 2009; Pauly and Keegstra, 2010; Steen et al., 2010). However, a large number of existing industrial enzymes are not compatible with many highly effective pre-treatment strategies, such as high temperatures and ionic liquid pre-treatment, and require substantial post-processing in order to make these substrates amenable to their use. "
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    ABSTRACT: Production of biofuels via enzymatic hydrolysis of complex plant polysaccharides is a subject of intense global interest. Microbial communities are known to express a wide range of enzymes necessary for the saccharification of lignocellulosic feedstocks and serve as a powerful reservoir for enzyme discovery. However, the growth temperature and conditions that yield high cellulase activity vary widely, and the throughput to identify optimal conditions has been limited by the slow handling and conventional analysis. A rapid method that uses small volumes of isolate culture to resolve specific enzyme activity is needed. In this work, a high throughput nanostructure-initiator mass spectrometry (NIMS)-based approach was developed for screening a thermophilic cellulolytic actinomycete, Thermobispora bispora, for β-glucosidase production under various growth conditions. Media that produced high β-glucosidase activity were found to be I/S + glucose or microcrystalline cellulose (MCC), Medium 84 + rolled oats, and M9TE + MCC at 45°C. Supernatants of cell cultures grown in M9TE + 1% MCC cleaved 2.5 times more substrate at 45°C than at all other temperatures. While T. bispora is reported to grow optimally at 60°C in Medium 84 + rolled oats and M9TE + 1% MCC, approximately 40% more conversion was observed at 45°C. This high throughput NIMS approach may provide an important tool in discovery and characterization of enzymes from environmental microbes for industrial and biofuel applications.
    Full-text · Article · Dec 2013 · Frontiers in Microbiology
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    • "The main contributors to the high cost of cell wall–derived glucose are low sugar density of the biomass, cell wall recalcitrance to enzymatic hydrolysis and medium content in cellulose. Each factor either impacts transportation or requires intensive use of energy and chemicals for processing (Blanch et al., 2008; Klein-Marcuschamer et al., 2010; Searcy et al., 2007). Therefore, enhancement of polysaccharide accumulation in raw biomass and improvement of biomass digestibility will have important beneficial impacts on the cost of lignocellulosic biofuels production (Blanch et al., 2011; Klein-Marcuschamer et al., 2010). "
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    ABSTRACT: Lignocellulosic biomass was used for thousands of years as animal feed and is now considered a great sugar source for biofuels production. It is composed mostly of secondary cell walls built with polysaccharide polymers that are embedded in lignin to reinforce the cell wall structure and maintain its integrity. Lignin is the primary material responsible for biomass recalcitrance to enzymatic hydrolysis. During plant development, deep reductions of lignin cause growth defects and often correlate with the loss of vessel integrity that adversely affects water and nutrient transport in plants. The work presented here describes a new approach to decrease lignin content while preventing vessel collapse and introduces a new strategy to boost transcription factor expression in native tissues. We used synthetic biology tools in Arabidopsis to rewire the secondary cell network by changing promoter-coding sequence associations. The result was a reduction in lignin and an increase in polysaccharide depositions in fibre cells. The promoter of a key lignin gene, C4H, was replaced by the vessel-specific promoter of transcription factor VND6. This rewired lignin biosynthesis specifically for vessel formation while disconnecting C4H expression from the fibre regulatory network. Secondly, the promoter of the IRX8 gene, secondary cell wall glycosyltransferase, was used to express a new copy of the fibre transcription factor NST1, and as the IRX8 promoter is induced by NST1, this also created an artificial positive feedback loop (APFL). The combination of strategies-lignin rewiring with APFL insertion-enhances polysaccharide deposition in stems without over-lignifying them, resulting in higher sugar yields after enzymatic hydrolysis.
    Full-text · Article · Nov 2012 · Plant Biotechnology Journal
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    • "Polysaccharides are major components of biomass and detritus in aquatic ecosystems and their microbial degradation constitutes one of the key bottlenecks in the carbon cycle [1], [2]. Better understanding of the microbial types and their biochemical machinery involved in the degradation of polysaccharides is also of special interest for cost-effective biofuel production from terrestrial plants and algae [3]–[5]. Laboratory-based experiments on cultured isolates have been traditional sources of information on polysaccharide-degrading microbial taxa and enzymes, but they represent only a minor fraction of the active players in the carbon cycling in nature [6]. "
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    ABSTRACT: Microbial hydrolysis of polysaccharides is critical to ecosystem functioning and is of great interest in diverse biotechnological applications, such as biofuel production and bioremediation. Here we demonstrate the use of a new, efficient approach to recover genomes of active polysaccharide degraders from natural, complex microbial assemblages, using a combination of fluorescently labeled substrates, fluorescence-activated cell sorting, and single cell genomics. We employed this approach to analyze freshwater and coastal bacterioplankton for degraders of laminarin and xylan, two of the most abundant storage and structural polysaccharides in nature. Our results suggest that a few phylotypes of Verrucomicrobia make a considerable contribution to polysaccharide degradation, although they constituted only a minor fraction of the total microbial community. Genomic sequencing of five cells, representing the most predominant, polysaccharide-active Verrucomicrobia phylotype, revealed significant enrichment in genes encoding a wide spectrum of glycoside hydrolases, sulfatases, peptidases, carbohydrate lyases and esterases, confirming that these organisms were well equipped for the hydrolysis of diverse polysaccharides. Remarkably, this enrichment was on average higher than in the sequenced representatives of Bacteroidetes, which are frequently regarded as highly efficient biopolymer degraders. These findings shed light on the ecological roles of uncultured Verrucomicrobia and suggest specific taxa as promising bioprospecting targets. The employed method offers a powerful tool to rapidly identify and recover discrete genomes of active players in polysaccharide degradation, without the need for cultivation.
    Full-text · Article · Apr 2012 · PLoS ONE
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