12 research outputs found
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Characterization of the organic-sulfur-degrading enzymes
The immediate objective of this project is to characterize and purify the enzymes involved in degrading organic sulfur in coal from two well characterization organic sulfur degrading strains, of Rhodococces rhodochorous IGTS8 and K3B. We believe that characterization and purification of these enzymes may provide valuable information that will lead to developing or isolating better strains for desulfurization of coal. Our recent results imply that the IGTS8 enzymes are firmly attached to the cell wall. For coal desulfurization it is better to have a microorganism that can secrete its desulfurization enzymes into the medium. The enzymes could permeate into coal much better than a bacterial cell. We seek that the isolation of a mutant of IGTS8 which can release the desulfurization enzymes in the cultural medium. During this period, we carried out more electron microscope analysis of IGTS8 and related species. These strains grow very poorly in DBT medium as well as in medium containing high sulfate concentration. Cells used for EM analysis were cultured in rich medium with glucose but found that there is no protruding structures on the cells of R. rhodochorous 184 and 13808. We believe that we should also examine the 183 and 13808 cells that have been cultured in the presence of DBT
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Genetic engineering of sulfur-degrading Sulfolobus
The objectives of the proposed research is to first establish a plasmid-mediated genetic transformation system for the sulfur degrading Sulfolobus, and then to clone and overexpress the genes encoding the organic-sulfur-degrading enzymes from Sulfolobus- as well as from other microorganisms, to develop a Sulfolobus-based microbial process for the removal of both organic and inorganic sulfur from coal
A constitutive catabolite repression mutant of a recombinant Saccharomyces cerevisiae strain improves xylose consumption during fermentation
Efficient xylose utilisation by microorganisms is of importance to the lignocellulose fermentation industry. The aim of this work was to develop constitutive catabolite repression mutants in a xylose-utilising recombinant Saccharomyces cerevisiae strain and evaluate the differences in xylose consumption under fermentation conditions. S. cerevisiae YUSM was constitutively catabolite repressed through specific disruptions within theMIG1 gene. The strains were grown aerobically in synthetic complete medium with xylose as the sole carbon source. Constitutive catabolite repressed strain YCR17 grew four-fold better on xylose in aerobic conditions than the control strain YUSM. Anaerobic batch fermentation in minimal medium with glucose-xylose mixtures and N-limited chemostats with varying sugar concentrations were performed. Sugar utilisation and metabolite production during fermentation were monitored. YCR17 exhibited a faster xylose consumption rate than YUSM under high glucose conditions in nitrogen-limited chemostat cultivations. This study shows that a constitutive catabolite repressed mutant could be used to enhance the xylose consumption rate even in the presence of high glucose in the fermentation medium. This could help in reducing fermentation time and cost in mixed sugar fermentation.Vasudevan Thanvanthri Gururajan, Marie-F. Gorwa-Grauslund, Bärbel Hahn-Hägerdal, Isak S. Pretorius and Ricardo R. Cordero Oter