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Genome sequencing of a variety of fungi is a major initiative currently supported by the Department of Energy’s Joint Genome Institute. Encoded within the genomes of many fungi are upwards of 200+ enzymes called glycoside hydrolases (GHs). GHs are known for their ability to hydrolyze the polysaccharide components of lignocellulosic biomass. Production of ethanol and “next generation” biofuels from...
Corn stover, the above-ground, non-grain portion of the crop, is a large, currently available source of biomass that potentially could be collected as a biofuels feedstock. Biomass conversion process economics are directly affected by the overall biochemical conversion yield, which is assumed to be proportional to the carbohydrate content of the feedstock materials used in the process. Variability...
Exoglucanases are key enzymes required for the efficient hydrolysis of crystalline cellulose. It has been proposed that exoglucanases hydrolyze cellulose chains in a processive manner to produce primarily cellobiose. Usually, two functional modules are involved in the processive mechanism: a catalytic module and a carbohydrate-binding module (CBM). In this report, single molecule tracking techniques...
The Department of Energy’s Office of the Biomass Program has set goals of making ethanol cost competitive by 2012 and replacing 30% of 2004 transportation supply with biofuels by 2030. Both goals require improvements in conversions of cellulosic biomass to sugars as well as improvements in fermentation rates and yields. Current best pretreatment processes are reasonably efficient at making the cellulose/hemicellulose/lignin...
Dimethylsulfoxide-solubilized polysaccharides from delignified corn stover and aspen were characterized. The biomass was delignified by two different techniques; a standard acid chlorite and a pulp and paper QPD technique comprising chelation (Q), peroxide (P), and acid-chlorite (D). Major polysaccharides in all fractions were diversely substituted xylan. Xylan acetylation was intact after chlorite...
The crystallinity index of cellulose is an important parameter to establish because of the effect this property has on the utilization of cellulose as a material and as a feedstock for biofuels production. However, it has been found that the crystallinity index varies significantly depending on the choice of instrument and data analysis technique applied to the measurement. We introduce in this study...
l-Arabinose is one of the sugars found in hemicellulose, a major component of plant cell walls. The ability to convert l-arabinose to ethanol would improve the economics of biomass to ethanol fermentations. One of the limitations for l-arabinose fermentation in the current engineered Saccharomyces cerevisiae strains is poor transport of the sugar. To better understand l-arabinose transport and use...
The filamentous fungi Trichoderma reesei and Penicillium funiculosum produce highly effective enzyme mixtures that degrade the cellulose and hemicellulose components of plant cell walls. Many fungal species produce a glycoside hydrolase family 7 (Cel7A) cellobiohydrolase, a class of enzymes that catalytically process from the reducing end of cellulose. A direct amino acid comparison of these two enzymes...
With the world’s focus on rapidly deploying second generation biofuels technologies, there exists today a good deal of interest in how yields, economics, and environmental impacts of the various conversion processes of lignocellulosic biomass to transportation fuels compare. Although there is a good deal of information regarding these conversion processes, this information is typically very difficult...
There exist large amounts of detergent fiber analysis data [neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL)] for many different potential cellulosic ethanol feedstocks, since these techniques are widely used for the analysis of forages. Researchers working in the area of cellulosic ethanol are interested in the structural carbohydrates in a feedstock (principally...
Analysis of variously pretreated corn stover samples showed neutral to mildly acidic pretreatments were more effective at removing xylan from corn stover and more likely to maintain the acetyl to xylopyranosyl ratios present in untreated material than were alkaline treatments. Retention of acetyl groups in the residual solids resulted in greater resistance to hydrolysis by endoxylanase alone, although...
We have studied rapid calibration models to predict the composition of a variety of biomass feedstocks by correlating near-infrared (NIR) spectroscopic data to compositional data produced using traditional wet chemical analysis techniques. The rapid calibration models are developed using multivariate statistical analysis of the spectroscopic and wet chemical data. This work discusses the latest versions...
As biorefining conversion technologies become commercial, feedstock availability, supply system logistics, and biomass material attributes are emerging as major barriers to the availability of corn stover for biorefining. While systems do exist to supply corn stover as feedstock to biorefining facilities, stover material attributes affecting physical deconstruction, such as densification and post-harvest...
The Biomass Refining Consortium for Applied Fundamentals and Innovation, with members from Auburn University, Dartmouth College, Michigan State University, the National Renewable Energy Laboratory, Purdue University, Texas A&M University, the University of British Columbia, and the University of California at Riverside, has developed comparative data on the conversion of corn stover to sugars...
It has previously been shown that the improved digestibility of dilute acid pretreated corn stover is at least partially due to the removal of xylan and the consequent increase in accessibility of the cellulose to cellobiohydrolase enzymes. We now report on the impact that lignin removal has on the accessibility and digestibility of dilute acid pretreated corn stover. Samples of corn stover were subjected...
There are two well studied mechanisms that are used by cellulolytic microorganisms to degrade the cellulose present in plant cell walls and a third less well studied oxidative mechanism used by brown rot fungi. The well studied mechanisms use cellulases to hydrolyze the β-1,4 linkages present in cellulose, however the way in which cellulases are presented to the environment are quite different for...
Technoeconomic analysis has been used to guide the research and development of lignocellulosic biofuels production processes for over two decades. Such analysis has served to identify the key technical barriers for these conversion processes so that research can be targeted most effectively on the pertinent challenges. The tools and methodology used to develop conceptual conversion processes and analyze...
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