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  • 1
    Electronic Resource
    Electronic Resource
    An unusual formaldehyde oxidizing system in Rhodococcus erythropolis grown on compounds containing methyl groups (1984)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 25 (1984), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract During utilization of compounds containing methyl groups, the non-methylotrophic bacteria Rhodococcus erythropolis oxidized the methyl groups entirely to carbon dioxide. This oxidation was linked to the presence of an NAD-dependent formaldehyde dehydrogenase activity which was lost on dialysis. The activity could be restored by the addition of boiled extract but not by adding the known cofactors glutathione or tetrahydrofolate.A further dehydrogenase activity with formaldehyde as substrate was found in ethanolgrown cells. This activity could be differentiated from that in methyl group metabolizing cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1984.tb01467.x
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  • 2
    Electronic Resource
    Electronic Resource
    Ethanol production from xylose with a pyruvate-formate-lyase mutant of Klebsiella planticola carrying a pyruvate-decarboxylase gene from Zymomonas mobilis (1989)
    Springer
    Applied microbiology and biotechnology 31 (1989), S. 152-157 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Grown anaerobically on d-xylose, Klebsiella planticola ATCC 33531 produced acetate, formate, lactate, CO2 and ethanol as major end-products. A Mu-insertion mutant which lacked pyruvate-formate-lyase showed among its fermentation products more than 70% d-lactate with residual acetate, 2,3-butanediol, and traces of ethanol, formate, and CO2. After the introduction of a plasmid carrying the gene for the enzyme pyruvate decarboxylase from Zymomonas mobilis, this Klebsiella mutant became an efficient ethanol producer. The recombinant strain produced 387 mM ethanol from 275 mM xylose in 80 h, about 83% of the theoretical maximal yield. Furthermore, this mutant consumed more than double the amount of xylose (41 g/l) compared to the wild-type, due to reduced production of inhibiting acids during growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262454
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  • 3
    Electronic Resource
    Electronic Resource
    Limitations during hydroxybutyrate converison to isoleucine with Corynebacterium glutamicum, as analysed by the formation of by-products (1989)
    Springer
    Applied microbiology and biotechnology 31 (1989), S. 458-462 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Upon the addition of 2-hydroxybutyrate as precursor to strain DL4 of Corynebacterium glutamicum not only isoleucine is secreted, but also the biosynthetic intermediates 2-ketobutyrate (max. 3 mM) and 2-keto-3-methylvalerate (max. 5 mM). In addition, the decarboxylation products of several biosynthetic intermediates are formed. This decarboxylation occurs in part chemically. Due to the accumulation of 2-keto-3-methylvalerate and its decarboxylation product the following aminating reaction yielding isoleucine was assayed for limitation. The metabolite secretion of strains with a threefold increased transaminase activity obtained by genetic engineering was unaffected. The equilibrium constant of the transaminase reaction was determined as 0.5 with enriched enzyme, revealing that the reaction is nearly freely reversible and apparently not rate-limiting. From these facts it is concluded that the additional step of isoleucine secretion is most probably limiting and this has not been considered so far in any isoleucine production process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270776
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of ethanol on the activities of 3-hydroxy-3-methylglutaryl-coenzyme A-reductase and squalene-hopene-cyclase in Zymomonas mobilis (1989)
    Springer
    Applied microbiology and biotechnology 30 (1989), S. 170-175 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The influence of different primary aliphatic alcohols on the activities of two key enzymes in hopanoid biosynthesis of Zymomonas mobilis was investigated. By use of 14C- and 3H-labelled substrates the enzymes 3-hydroxy-3-methylglutaryl-CoA-reductase and squalene-hopenecyclase were detected with activities of 1.6 pmol x (min x mg protein)-1 and 2.3 pmol x- (min x mg protein)-1, respectively. Cells grown in the presence of 6% (v/v) ethanol did not show higher activities of these enzymes than cells grown in the presence of 1% (v/v) ethanol. Furthermore, 3-hydroxy-3-methylglutaryl-CoA-reductase was not activated by ethanol. However, ethanol activated the squalene-hopene-cyclase when added to the enzyme test system. Besides ethanol, propanol also had a positive effect on the squalene-hopene-cyclase: the enzyme's activity increased 1.7-fold in the presence of either alcohol at a concentration of 6% (v/v). This corresponded with a similar increase of hopanoid content of whole cells when grown in the presence of 6% (v/v) added ethanol or propanol. These results indicated that the squalene-hopene-cyclase has a regulatory function in the alcohol dependent hopanoid biosynthesis of Z. mobilis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264007
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of alcohols and temperature on the hopanoid content of Zymomonas mobilis (1986)
    Springer
    Applied microbiology and biotechnology 25 (1986), S. 32-36 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The influence of different culture conditions on the hopanoid content of Zymomonas mobilis was investigated in batch cultures. With a gas-liquid chromatographic method it could be shown that the content of 1,2,3,4-tetrahydroxypentane-29-hopane (THBH) reached a maximum value in the stationary phase due to the high level of ethanol accumulated in the medium. The hopanoid content increased sharply with the addition of ethanol to the culture. Ethanol was shown to be the most effective of the alcohols tested in causing an increase of the hopanoid content. Furthermore, an alteration of the incubation temperature from 14° to 37°C also caused an increase of the amount of hopanoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252509
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  • 6
    Electronic Resource
    Electronic Resource
    Production of acetic acid by Acetogenium kivui (1987)
    Springer
    Applied microbiology and biotechnology 27 (1987), S. 229-234 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The formation of acetic acid by the thermophilic nonsporeforming homoacetogenic bacterium Acetogenium kivui was studied under various conditions. In pH-controlled batch fermentation at pH 6.4 this bacterium was able to produce up to 625 mM of acetic acid from glucose within 50–60 h. The value of μ max obtained was about 0.17 h-1, the yield was about 2.55 mol of acetic acid per mol of glucose utilized. In continuous fermentation both substrate concentration and dilution rate (D) influenced the yield of acetate and the stationary concentration: a glucose concentration of 67 mM at D=0.09 h-1 resulted in 2.82 mol acetate/mol glucose and 190 mM acetate at a production rate of 17.1 mM/1 h. When the dilution rate was increased the production rate reached a maximal value of 43.2 mM/1 h at D=0.32 h-1. At a glucose concentration of 195 mM the dependence of yield upon dilution rate followed a similar pattern and an acetate concentration of 420 mM could be obtained. Enzymatic studies indicate that in A. kivui pyruvate ferredoxin-oxidoreductase and acetate kinase are inhibited at acetate concentrations higher than 800 mM. Based on these results a fed-batch fermentation was developed, which allowed to produce more than 700 mM acetic acid within 40–50 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252923
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  • 7
    Electronic Resource
    Electronic Resource
    Microbial production of l-leucine from α-ketoisocaproate by Corynebacterium glutamicum (1987)
    Springer
    Applied microbiology and biotechnology 25 (1987), S. 352-356 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A process for l-leucine production was studied using Corynebacterium glutamicum for the conversion of α-ketoisocaproate. When this precursor was added to the culture medium in a concentration of 20 g/l about 16 g/l l-leucine were formed after a fermentation time of 57 h and the molar yield was 91%. Using a fed-batch culture it was possible to produce 24 g/l of l-leucine from 32 g/l of α-ketoisocaproate within 23 h. Enzymatic studies indicate that in this glutamate-producing bacterium α-ketoisocaproate is converted into l-leucine via the transaminase B reaction and l-glutamate is regenerated by the glutamate dehydrogenase. By the addition of α-ketoisocaproate to the culture medium the specific activity of transaminase B was increased threefold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252546
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  • 8
    Electronic Resource
    Electronic Resource
    Regulation of acetohydroxy acid synthase in Corynebacterium glutamicum during fermentation of α-ketobutyrate to l-isoleucine (1987)
    Springer
    Applied microbiology and biotechnology 25 (1987), S. 346-351 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Corynebacterium glutamicum ATCC 13 032 produces 13 g/l l-isoleucine from 200 mM α-ketobutyrate as a synthetic precursor. In fed batch cultures up to 19 g/l l-isoleucine is formed. For optimal conversion the addition of 0.3 mM l-valine plus 0.3 mM l-leucine to the fermentation medium is required. The affinity constants for the acetohydroxy acid synthase (AHAS) were determined. (This enzyme directs the flow of α-ketobutyrate plus pyruvate towards l-isoleucine and that of two moles of pyruvate to l-valine and l-leucine, respectively.) For α-ketobutyrate the K m is 4.8×10-3 M, and V max 0.58 U/mg, for pyruvate the K m is 8.4×10-3 M, and V max 0.37 U/mg. Due to these characteristics the presence of high α-ketobutyrate concentrations apparently results in a l-valine, l-leucine deficiency. This in turn leads to a derepression of the AHAS synthesis from 0.03 U/mg to 0.29 U/mg and high l-isoleucine production is favoured. The derepression of the AHAS synthesis induced by the l-valine, l-leucine shortage was directly proven with a l-valine, l-leucine, l-isoleucine auxotrophic mutant where the starvation of each amino acid resulted in an increased AHAS level. This is in accordance with the fact that only one AHAS enzyme could be verified by chromatographic and electrophoretic separations as being responsible for the synthesis of all three branched-chain amino-acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252545
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  • 9
    Electronic Resource
    Electronic Resource
    Junctions of catabolic and anabolic pathways in Zymomonas mobilis: phosphoenolpyruvate carboxylase and malic enzyme (1989)
    Springer
    Applied microbiology and biotechnology 31 (1989), S. 529-536 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The synthesis of oxalacetate and malate in the ethanol-producing bacterium Zymomonas mobilis have been investigated. Cell-free extracts were examined for pyruvate carboxylase, phosphoenolpyruvate (PEP) carboxylase, PEP carboxytransphosphorylase, PEP carboxykinase, and malic enzyme, but only PEP carboxylase and nicotine adenine dinucleotide (NAD)-dependent malic enzyme activities could be detected. The PEP carboxylase, partially purified from extracts, was not affected by acetyl-coenzyme A. Intermediates of the tricarboxylic acid cycle and aspartate inhibited the enzyme competitively with PEP. Of these, citrate and α-ketoglutarate were the strongest inhibitors. The physiological roles of PEP carboxylase and malic enzyme in Z. mobilis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270789
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  • 10
    Electronic Resource
    Electronic Resource
    Formation and degradation of gluconate by Zymomonas mobilis (1988)
    Springer
    Applied microbiology and biotechnology 27 (1988), S. 378-382 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Zymomonas mobilis ATCC 29191 is able to degrade gluconate but cannot use it as a single carbon and energy source. Gluconate is phosphorylated by a gluconate kinase (EC 2.7.1.12) and the resulting 6-phosphogluconate is further catabolized to yield about 0.8 mol ethanol per mol of gluconate, considerable amounts of acetate and acetoin. This product spectrum agrees with the theoretical yield of only one reduction equivalent if gluconate is phosphorylated by a kinase and subsequently metabolized via the Entner-Doudoroff pathway. Furthermore, Z. mobilis contains a membrane-bound enzyme system which is able to oxidize glucose to gluconate. Cell-free extracts were active in an assay system with Wurster's blue as electron acceptor, and various aldoses as well as maltose, mannitol and sorbitol could be oxidized. The affinity for sorbitol was very low (K m =330 mM) but reasonable for glucose (K m =2.8 mM). The pH optimum for the glucose-oxidizing reaction was 6.5, while that for sorbitol oxidation was 5.5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00251772
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