• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2004.06a
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• pp.257-257
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• 2004

• Proceedings of the Microbiological Society of Korea Conference
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• 2005.05a
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• pp.206.4-206
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• 2005

• The Korea Genome Conference
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• 2006.09a
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• pp.56-56
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• 2006

• KSBB Journal
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• v.5 no.4
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• pp.335-339
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• 1990

In order to develop economic processes for ethanol production from starch, a simultaneous saccharification and fermentation(SSF) process using Zymomonas mobilis and amyloglucosidase (AMG) was studied in semibatch modes using cell recycle. The cell recycle was carried out by adopting two different methods; microfiltration and settling. The cell recycle using microfiltration revealed higher productivity(5.4 g/l/h) than that using a settler(4.3 g/l/h). Taking the large-scale ethanol fermentation into account, the semibatch process using microfiltration system appeared most promising among others with respect to ethanol productivity, feasibility of scale-up and simplification of operation.

• Korean Journal of Microbiology
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• v.41 no.2
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• pp.93-98
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• 2005

The sphingosine kinase gene, which is 969-nucleotide long, was identified during the whole genome sequencing of Sphingomonas chungbukensis DJ77. The amino acid sequence showed the identity of $55\%$ with that of Zymomonas mobilis subsp. mobilis ZM4. C2, C3, and C5 domains of eukaryotic sphingosine kinase were found in sphingosine kinase from Sphingomonas chungbukensis DI77. One of these three conserved sites, GGDG, was predicted as a ATP-binding site, and the functions of the others were unknown currently. The phylogenetic tree constructed by ClustalX indicated that the sphingosine kinase of S. chungbukensis DJ77 was near the phylogenetic group COG1597, and did not belong to the group of diacylglycerol kinase of the same strain. The recombinant sphingosine kinase was expressed in Escherichia coli, but it was made in form of inclusion body.

• Journal of Life Science
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• v.25 no.11
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• pp.1290-1297
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• 2015

Studies of the inactivation of a gene encoding pyruvate decarboxylase, pdc, in an ethanol-producing bacterium, Zymomonas mobilis, identified a mutant strain with 50% reduced PDC activity. To evaluate the possibility of a carbon-flux shift from an ethanol pathway toward higher value fermentation products, including pyruvate, succinate, and lactate, fermentation studies were carried out. Despite attempts to silence pdc expression in the wild-type strain ZM4 using cat-inserted pdc and pdc-deleted homologs by electroporation, the strain isolated showed partial gene activation. Fermentation experiments with the PDC mutant strain showed that the reduced expression level of PDC activity resulted in decreased rates of substrate uptake and ethanol production, together with increased pyruvate accumulation of 2.5 g l^-1 , although lactate and succinate concentrations were not significantly enhanced in these modified strains. Despite numerous attempts, no strains were isolated in which complete pdc inactivation occurred. This result indicates that the ethanol fermentation pathway of this bacterium is totally dependent on the activity of the PDC enzyme. To ensure a redox balance of intracellular NAD and NADH levels, other enzymes, such as lactate dehydrogenase for lactate, and enzymes involved in the production of succinic acid, such as pyruvate dehydrogenase (PDH) and malic enzymes, may be needed for their increased end-product production.