Obtaining bioethanol from cellulosic biomass involves numerous steps, among which the enzymatic conversion of the polymer to individual sugar units has been a main focus of the biotechnology industry. Among the cellulases that break down the polymeric cellulose are endoglucanases that act synergistically for subsequent hydrolytic reactions. The endoglucanases that have garnered relatively more attention are those that can withstand high temperatures, i.e., are thermostable. Although our understanding of thermostability in endoglucanases is incomplete, some molecular features that are responsible for increased thermostability have been recently identified. This review focuses on the investigations of endoglucanases and their implications for biofuel applications.
Plant expression of thermostable endoglucanase (E1) has been proposed for improved conversion of lignocellulose to ethanol for fuel production. Residues of E1-expressing maize may affect ecological services (e.g., C mineralization and biogeochemical cycling) on soils where they occur. Therefore, the activity of residual E1 was investigated using soils amended with bacterial and plant-solubilized E1 compared with soil endogenous activity and residual activity from a mesostable cellulase (Aspergillus and Trichoderma spp.). An optimized analytical method involving a carboxymethyl cellulose substrate and dinitrosalicylic acid detection effectively assayed endoglucanase activity in amended and unamended soils and was used for determining E1 activity in 3 representative soils. The effect of E1 on soil carbon mineralization was determined by comparing CO(2) evolution from soils amended with transgenic E1-expressing and wild-type maize tissue. Extraction and recovery of the mesostable comparator, bacterial E1, and plant-soluble E1 showed nearly complete loss of exogenous endoglucanase activity within a 24-h period. Carbon mineralization indicated no significant difference between soils amended with either the transgenic E1 or wild-type maize tissue. These results indicate that maize residues expressing up to 30 µg E1/g tissue negligibly affect soil endoglucanase activity and CO(2) respiration for representative soils where transgenic E1 maize may be grown.
Wikipedia is a web‐based, free‐content encyclopedia that is openly editable and, thus, provides a unique platform for collaborations. Wikipedia projects are increasingly being integrated into upper‐level courses across the country to explore advanced concepts, communicate science, and provide high‐quality information to the public. Here we outline a project intended to reinforce and communicate concepts of risk assessment as it was implemented in a multidisciplinary graduate course and, based on observations from the instructors and results from a post‐project reflection survey and exit‐interview, we evaluated how to better enable student learning in future Wikipedia projects. A networked Wikipedia project was introduced to a graduate‐level course in human and environmental safety as an alternative to traditional team projects. Students independently authored Wikipedia entries and then collaborated in editing the result prior to publication to the World Wide Web. Project outcomes indicated general success by the students in developing high quality content, but there is a need to improve the background and supporting materials provided to students to better enable their use of Wikipedia writing and editing tools. There was also opportunity to improve quality of the students’ work product by emphasizing the major course concepts that should be applied in the project and by more clearly addressing common questions that relate to the Wikipedia “process.” Student learning curves and computer literacy dictated the pace at which the project moved forward; so for the less computer literate students, effort tended to skew toward learning the tool rather than applying course concepts.
Biofeedstocka plant-based material used in biorefineries as an energy source.Dissipationthe biotic or abiotic inactivation of a biomolecule that prevents detection and functionality.EEC (estimated environmental concentration)a realistic, conservative exposure estimate based on the expression level or concentration (exudate) of the protein, mass of residue or volume loaded, and the applicable quantity of receiving environment (soil).Endogenousproduced from within, native.Enzyme Activity Assaya method for detecting functional enzymes by incubating with a substrate and quantifying some assessment endpoint of catalysis (e.g. colorimetric, dye, fluorogenic, viscosity, mass-balance).Exogenousadded from a foreign source.Mesophiliccharacterized as developing or functioning at moderate environmental temperatures where most organisms exist (generally 20-45 o C).Persistencedetection of a biomolecule over time in a given environmental system (related to dissipation).Thermophilic -"heat-loving"characterized as developing or functioning at high temperatures not sustainable to most organisms (generally 45-120 o C).Transgenican organism that expresses a heterologous gene, often contrasted with traditional breeding.
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