Yao S.,Technical University of Denmark |
Journal of Molecular Microbiology and Biotechnology | Year: 2010
Thermoanaerobacter mathranii contains four genes, adhA, adhB, bdhA and adhE, predicted to code for alcohol dehydrogenases involved in ethanol metabolism. These alcohol dehydrogenases were characterized as NADP(H)-dependent primary alcohol dehydrogenase (AdhA), secondary alcohol dehydrogenase (AdhB), butanol dehydrogenase (BdhA) and NAD(H)-dependent bifunctional aldehyde/alcohol dehydrogenase (AdhE), respectively. Here we observed that AdhE is an important enzyme responsible for ethanol production in T. mathranii based on the constructed adh knockout strains. An adhE knockout strain fails to produce ethanol as a fermentation product, while other adh knockout strains showed no significant difference from the wild type. Further analysis revealed that the ΔadhE strain was defective in aldehyde dehydrogenase activity, but still maintained alcohol dehydrogenase activity. This showed that AdhE is the major aldehyde dehydrogenase in the cell and functions predominantly in the acetyl-CoA reduction to acetaldehyde in the ethanol formation pathway. Finally, AdhE was conditionally expressed from a xylose-induced promoter in a recombinant strain (BG1E1) with a concomitant deletion of a lactate dehydrogenase. Overexpressions of AdhE in strain BG1E1 with xylose as a substrate facilitate the production of ethanol at an increased yield. Copyright © 2010 S. Karger AG, Basel. Source
Yao S.,Technical University of Denmark |
Applied Microbiology and Biotechnology | Year: 2010
Thermoanaerobacter mathranii can produce ethanol from lignocellulosic biomass at high temperatures, but its biotechnological exploitation will require metabolic engineering to increase its ethanol yield. With a cofactor-dependent ethanol production pathway in T. mathranii, it may become crucial to regenerate cofactor to increase the ethanol yield. Feeding the cells with a more reduced carbon source, such as mannitol, was shown to increase ethanol yield beyond that obtained with glucose and xylose. The ldh gene coding for lactate dehydrogenase was previously deleted from T. mathranii to eliminate an NADH oxidation pathway. To further facilitate NADH regeneration used for ethanol formation, a heterologous gene gldA encoding an NAD+-dependent glycerol dehydrogenase was expressed in T. mathranii. One of the resulting recombinant strains, T. mathranii BG1G1 (Δldh, P xyl GldA), showed increased ethanol yield in the presence of glycerol using xylose as a substrate. With an inactivated lactate pathway and expressed glycerol dehydrogenase activity, the metabolism of the cells was shifted toward the production of ethanol over acetate, hence restoring the redox balance. It was also shown that strain BG1G1 acquired the capability to utilize glycerol as an extra carbon source in the presence of xylose, and utilization of the more reduced substrate glycerol resulted in a higher ethanol yield. © 2010 Springer-Verlag. Source
BioGasol | Date: 2012-06-22
The invention relates to a method for isolating a microorganism containing a known genetic element. The method employs several rounds of 1) dilution of a mixed culture containing the selected microorganism in several replicates, 2) growing the replicates, 3) detecting the organism in at least one of the replicates and repeating steps 1) through 3) until the organism can be isolated by standard procedures.
BioGasol | Date: 2010-01-13
The invention relates to an apparatus for treating material by cutting, soaking and/or washing of the material, wherein the apparatus comprises a receptacle (
BioGasol | Date: 2010-01-12
The present invention relates to an apparatus, which can be part of a pre-treatment system in a plant for the production of fuels, e. g. bio-ethanol, derived from plant biomass, e. g. first generation crops, such as grain, sugarcane and corn or second generation crops such as lignocellulosic biomass. The invention relates to an apparatus for processing, such as fluffing and mixing, at least two media, such as a solid, e. g. biomass, and a fluid, e. g. steam, so as to rendering the first medium susceptible to efficient receiving of energy and/or mass which is provided by localized release of the second medium. Although the description of the present invention focuses on biomass, it is envisaged that the invention is generally applicable to control the mixing of at least two media by crossing their stream of while dispersing at least one of them.