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Structural determination of enzymes important in bio-fuel production
Environmental and economic reasons motivate focused research on biofuel production. The new research programme MicroDrivE – Microbially Derived Energy, offers a series of MSc projects within bio-preservation, enzymatic pre-treatments, ethanol fermentation, bioprocessing of byproducts, biogas production and fertility effects of bioresidues. The projects are supervised by scientists from the Departments of Microbiology, Molecular Biology, and Chemistry at the Swedish University of Agricultural Sciences (SLU), Uppsala. MicroDrivE cooperates with a number of biotech and bioenergy companies. For information on the other MSc projects use the search function ”Fritext” to search for MicroDrive.
Background and goal
Due to the rapid decrease of global oil reserves and the excess of greenhouse gases in the atmosphere, there is an urgent need to replace fossil fuels with other fuels such as ethanol that can be produced from renewable resources. Today ethanol is produced mainly from sugar crops (sugar beets, sugar cane) and starch crops (e.g. corn, wheat, potato). However, to meet the needs of the future with such ethanol would require huge areas of agricultural land, and it may be considered unethical to use food for production of car fuel. Attention is therefore turning towards cellulose, which is abundantly available in plant biomass. Cheap materials could be used, for example agricultural wastes and energy crops (energiskog) etc. Cellulose materials, as well as starch, requires degradation of the polysaccharides to fermentable sugars before the fermentation to ethanol. This can be done with enzymes, which is more environmentally friendly than chemical treatment. However, very large quantities of enzymes are needed, especially with cellulose materials, and the enzyme cost is thus a critical factor.
The predominant source of cellulases for industrial applications is the filamentous fungus Hypocrea jecorina. It has an efficient mix of enzymes and is a very prolific protein producer. Industrial strains can make in the excess of 50 g per liter of extracellular enzymes. We have, in corporation with our industrial partner Danisco, for the past 8-9 years tried to optimize several enzymes for biomass conversion, mainly from H. jecorina. A more than ten-fold enzyme cost reduction has been achieved, mainly by optimizing enzyme production and enzyme mixtures, but also through biochemical improvements of several of the individual enzyme components.
Our main focus is to structurally characterize biomass-degrading enzymes from H. jecorina by x-ray crystallography, and we aim at obtaining the structures of as many as possible of these enzymes. The structural information, in combination with biochemical characterization, is used as guidelines for protein engineering towards enhanced performance in industrial applications, for example better pH and thermal stability.
Examples of three types of MSc projects:
1. Express, purify, biochemically characterize, and crystallize an enzyme.
2. Collect x-ray diffraction data on protein crystals of an enzyme and use this data to solve, build and refine its three-dimensional structure model.
3. Carry out bioinformatic characterization of an enzyme that we have solved the three-dimensional structure of, with the aim to identify features in the structure that might influence temperature stability and/or activity at extreme pHs.
Protein expression, protein purification, biochemical characterization, protein crystallization, x-ray data collection at one of the electron accelerators in Europe, structure building, refinement, analysis and comparisons using computer graphics.
We are looking for a student within the biochemistry, microbiology and biotechnology area interested in future technologies for bio-fuel production and environmental concerns.
For information on the Department of Molecular Biology, SLU, visit our Web-site: http:
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