Strain improvement for fermentation and biocatalysis processes by genetic engineering technology

Chiang, Shu-Jen

doi:10.1007/s10295-004-0131-z

Cited by 37 publications

(15 citation statements)

References 22 publications

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“…It is advantageous to use whole cells when complex transformations are involved that require the action of several enzymes organized in complex metabolic pathways and the presence of cellular cofactors (Borgne & Quintro, 2003;Chiang, 2004). In the 4S pathway, used as the basis of BDS research, there are two monooxygenases that require FMNH 2 .…”

Section: Introductionmentioning

confidence: 99%

Stabilization of water/gas oil emulsions by desulfurizing cells of Gordonia alkanivorans RIPI90A

et al. 2007

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It has been previously reported that resting-cells, non-proliferating cells, of Gordonia alkanivorans RIPI90A can convert dibenzothiophene (DBT) to 2-hydroxybiphenyl (2-HBP) via the 4S pathway in a biphasic system. The main goal of the current work was to study the behaviour of resting-cells of this strain in biphasic organic media. Resting-cells showed strong affinity for sulfurous organic substrates and were able to stabilize water/gas oil emulsions by attaching to the interface without decreasing the surface tension of their environment. This was consistent with the behaviour of the whole cells but not the surfactants, suggesting that microbial cell-mediated emulsification occurs. It was found that the emulsion-stabilizing activity of the resting-cells was influenced by the growth stage, but was not directly influenced by the metabolic activity of the resting-cells. This activity may be related to cell-surface hydrophobicity, which results from the unique chemical structure of the cell surface. In some biphasic biodesulfurization (BDS) bioreactors, emulsions are created without addition of any surfactant. Cell surface-mediated stabilization helps prolong the emulsions and therefore overcomes mass-transfer limitations in bioreactors. The simultaneous occurrence of emulsion-stabilizing and desulfurization activities of resting-cells was observed for what is believed to be the first time. The results suggest that this strain may have potential for the BDS of diesel oils.

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Section: Introductionmentioning

confidence: 99%

Stabilization of water/gas oil emulsions by desulfurizing cells of Gordonia alkanivorans RIPI90A

et al. 2007

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“…Currently no known examples of industrial production strains in which regulatory genes have been manipulated in order to increase polyketide production have been reported (10).…”

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confidence: 99%

Roles of rapH and rapG in Positive Regulation of Rapamycin Biosynthesis in Streptomyces hygroscopicus

Kuščer¹,

Coates²,

Challis³

et al. 2007

J Bacteriol

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Rapamycin is an important macrocyclic polyketide produced by Streptomyces hygroscopicus and showing immunosuppressive, antifungal, and antitumor activities as well as displaying anti-inflammatory and neuroregenerative properties. The immense pharmacological potential of rapamycin has led to the production of an array of analogues, including through genetic engineering of the rapamycin biosynthetic gene cluster. This cluster contains several putative regulatory genes. Based on DNA sequence analysis, the products of genes rapH and rapG showed high similarities with two different families of transcriptional activators, LAL and AraC, respectively. Overexpression of either gene resulted in a substantial increase in rapamycin biosynthesis, confirming their positive regulatory role, while deletion of both from the chromosome of S. hygroscopicus resulted in a complete loss of antibiotic production. Complementation studies indicated an essential role of the RapG regulator for rapamycin biosynthesis and a supportive role of RapH. A direct effect of rapH and rapG gene products on the promoter of the rapamycin polyketide synthase operon, rapA-rapB, was observed using the chalcone synthase gene rppA as a reporter system.

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“…Moreover, changes in the expression level of one gene can affect the optimal expression levels of other genes. Because most biological processes are regulated at the level of transcription (33), modification of gene expression and alteration of protein kinetic properties are the most widely adopted strategies to improve a strain for useful chemical production (5,41).…”

mentioning

confidence: 99%

Shuffling of Promoters for Multiple Genes To Optimize Xylose Fermentation in an Engineered Saccharomyces cerevisiae Strain

Lu¹,

Jeffries

2007

Appl Environ Microbiol

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We describe here a useful metabolic engineering tool, multiple-gene-promoter shuffling (MGPS), to optimize expression levels for multiple genes. This method approaches an optimized gene overexpression level by fusing promoters of various strengths to genes of interest for a particular pathway. Selection of these promoters is based on the expression levels of the native genes under the same physiological conditions intended for the application. MGPS was implemented in a yeast xylose fermentation mixture by shuffling the promoters for GND2 and HXK2 with the genes for transaldolase (TAL1), transketolase (TKL1), and pyruvate kinase (PYK1) in the Saccharomyces cerevisiae strain FPL-YSX3. This host strain has integrated xylose-metabolizing genes, including xylose reductase, xylitol dehydrogenase, and xylulose kinase. The optimal expression levels for TAL1, TKL1, and PYK1 were identified by analysis of volumetric ethanol production by transformed cells. We found the optimal combination for ethanol production to be GND2-TAL1-HXK2-TKL1-HXK2-PYK1. The MGPS method could easily be adapted for other eukaryotic and prokaryotic organisms to optimize expression of genes for industrial fermentation.

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Strain improvement for fermentation and biocatalysis processes by genetic engineering technology

Cited by 37 publications

References 22 publications

Stabilization of water/gas oil emulsions by desulfurizing cells of Gordonia alkanivorans RIPI90A

Stabilization of water/gas oil emulsions by desulfurizing cells of Gordonia alkanivorans RIPI90A

Roles of rapH and rapG in Positive Regulation of Rapamycin Biosynthesis in Streptomyces hygroscopicus

Shuffling of Promoters for Multiple Genes To Optimize Xylose Fermentation in an Engineered Saccharomyces cerevisiae Strain

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