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  • 1
    Electronic Resource
    Electronic Resource
    New Developments in the Synthesis of Natural and Unnatural Amino Acids (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 672 (1992), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Notes: Amino acids play an important role in biochemistry and chemistry. They are the building blocks of proteins and play an essential role in the regulation of the metabolism of living organisms.In general, it can be stated that microbial processes (fermentation) are the industrial production methods of choice for large-scale production of naturally occuring proteinogenic L-α-H-amino acids, while for the production of synthetic D- and/or L-α-H-amino acids, several other methods are highly competitive.At DSM, several routes, i.e., (chemoenzymatic) synthesis, towards L-α-H and D-α-H-amino acids have been elaborated since the midseventies.A general process for the synthesis of natural as well as synthetic optically pure amino acids has been developed, using an enzymatic kinetic resolution step on racemic amino acid amides as the key step. In this case, both enantiomers of the α-H-amino acids are prepared in one single step. This process has been commercialized since 1988.More recent developments using L- or D-amino peptidases in combination with amino acid amide racemases and an asymmetric transformation concept are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1992.tb35665.x
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  • 2
    Electronic Resource
    Electronic Resource
    Immobilization of Aminoacylase on an Anion Exchange Column to Be Used as a Chromatographic Reactor (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 799 (1996), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1996.tb33252.x
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetic aspects of glucose oxidation by Gluconobacter oxydans cells immobilized in calcium alginate (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 13-18 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Gluconobacter oxydans subspecies suboxydans (ATCC 621 H), when growing at high glucose concentrations, oxidizes this substrate incompletely and gluconic acid accumulates in the medium in almost stoichiometric amounts. Such cells were harvested and entrapped in various alginate gels. The preparation with the highest retention of glucose oxidizing activity was used in further studies with the aim of developing an efficient process for continuous gluconic acid production. The retention of activity increases (up to 95%) as the alginate concentration in the gel decreases or the cell/alginate weight ratio is enhanced. In the latter case, however, transport of oxygen to and inside the biocatalyst beads rapidly becomes rate-limiting and thus lowers the efficiency of the biocatalyst. Similarly, the efficiency decreases as the size of the biocatalyst beads increases. In no case rate-limitation by transport of glucose was found. Thus, biocatalyst activity per unit volume of support, diameter of the biocatalyst beads, and aeration efficiency are important parameters for reactor design.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00510565
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  • 4
    Electronic Resource
    Electronic Resource
    Bioformation of 4-hydroxybenzoate from 4-chlorobenzoate by Alcaligenes denitrificans NTB-1 (1986)
    Springer
    Applied microbiology and biotechnology 25 (1986), S. 289-294 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Strain NTB-1, identified as a Alcaligenes denitrificans sp., was isolated from a mixture of soil and sewage samples using 4-chlorobenzoate as sole carbon and energy source. Simultaneous adaptation experiments and enzyme studies revealed that 4-chlorobenzoate was converted to 4-hydroxybenzoate which was further oxidized yielding 3,4-dihydroxybenzoate. Bioformation of 4-hydroxybenzoate from 4-chlorobenzoate when 4-chlorobenzoate-grown cells were incubated with 4-chlorobenzoate under conditions of low and controlled oxygen concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00253665
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  • 5
    Electronic Resource
    Electronic Resource
    Degradation of 3-chloro-2-methylpropionic acid by Xanthobacter sp. CIMW 99 (1991)
    Springer
    Applied microbiology and biotechnology 36 (1991), S. 246-251 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Both stereoisomers of 3-chloro-2-methylpropionic acid (CMPA) and its methyl esters (MeCMPA) serve as growth substrates for a bacterial isolate (Xanthobacter sp. CIMW 99) when supplied as sole source of carbon and energy. Biodegradation of dl-CMPA and dl-MeCMPA was shown to be via a common pathway; an initial, constitutive, esterase converted the methyl ester to the corresponding carboxylic acid. Further metabolism required the activation of CMPA involving a CoA-, ATP-, Mg2+-dependent chloroacyl-CoA synthetase. Most noteworthy, it was the product of this reaction (3-chloro-2-methylpropionyl-CoA) that underwent hydrolytic dehalogenation to give 3-hydroxy-2-methylpropionyl-CoA (3-hydroxyisobutyryl-CoA). Further biodegradation proceeded by the action of a dehydrogenase on the CoA derivative to give methylmalonate-CoA-semialdahyde. Cells of CIMW 99 also contained a stable, constitutive, highly active 3-hydroxyisobutyrate dehydrogenase that was specific for the l(+) isomer. However, evidence is presented suggesting that this enzyme was not involved in the catabolism of the chlorinated substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164429
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  • 6
    Electronic Resource
    Electronic Resource
    Permeabilization and lysis of Pseudomonas pseudoalcaligenes cells by Triton X-100 for efficient production of d-malate (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 590-594 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Pseudomonas pseudoalcaligenes can only form d-malate from maleate after incubation of the cells with a solvent or a detergent. The effect of the detergent Triton X-100 on d-malate production was studied in more detail. The longer the cells were incubated with Triton X-100, the higher was the d-malate production activity, until the maximal malease activity was reached. Incubation of P. pseudoalcaligenes cells with Triton X-100 also resulted in an increase in the protein concentration of the supernatant, indicating that cell lysis had occurred. The rate at which the d-malate production activity increased was dependent on the Triton X-100 concentration and on the cell density. Also the rate at which lysis occurred depended on the Triton X-100 concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164759
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  • 7
    Electronic Resource
    Electronic Resource
    Production of 1-kestose with intact mycelium of Aspergillus phoenicis containing sucrose-1F-fructosyltransferase (1991)
    Springer
    Applied microbiology and biotechnology 35 (1991), S. 216-221 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Favourable reaction conditions for the enzymatic production of 1-kestose by sucrose-1F-fructosyltransferase, SFT (EC 2.4.1.99) from Aspergillus phoenicis CBS 294.80 mycelium were established. The intracellular enzyme SFT works best at 60°C, exhibits a relatively high thermostability and possesses an alkaline pH optimum. An invertase also present in the mycelium of A. phoenicis possesses an acidic pH optimum. Consequently, around pH 8.0 sucrose is converted mainly to 1-kestose and nystose while fructose is only formed in relatively small amounts. Under optimal conditions (55° C, pH 8.0 and an initial sucrose concentration of 750 g 1-1) a yield of about 300 g 1-kestose per 1.01 reaction mixture could be achieved after 8 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00184689
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  • 8
    Electronic Resource
    Electronic Resource
    Ochrobactrum anthropi NCIMB 40321: a new biocatalyst with broad-spectrum l-specific amidase activity (1993)
    Springer
    Applied microbiology and biotechnology 39 (1993), S. 296-300 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Of 125 microorganisms that were able to use α-hydroxy acid amides as sole nitrogen source, Ochrobactrum anthropi NCIMB 40321 was selected for its ability to hydrolyse racemic amides l-selectively. The substrate specificity of whole O. anthropi cells is remarkably wide and ranges from α-H-α-amino-, α-alkyl-α-amino, N-hydroxy-α-amino acid amides to α-hydroxy-acid amides. After 50% conversion, both the l-acids formed and the remaining d-amides were present in 〉99% enantiomeric excess, and ammonia accumulated in stoichiometric amounts. Using mandelic acid amide as a model substrate, the hydrolysis was optimized. Optimal rates were observed at pH 8.5 at 50°C. At higher temperatures the initial rate was even higher; however, fairly rapid inactivation occurred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192081
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  • 9
    Electronic Resource
    Electronic Resource
    The involvement of an enantioselective transaminase in the metabolism of D-3- and D-4-hydroxyphenylglycine inPseudomonas putida LW-4 (1988)
    Springer
    Applied microbiology and biotechnology 29 (1988), S. 224-230 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Pseudomonas putida LW-4, isolated on D-phenylglycine as sole carbon and energy source, was also able to grow on D-3-and D-4-hydroxyphenylglycine. Both D-3-and D-4-hydroxyphenylglycine were initially converted to the corresponding hydroxyphenylglyoxylates by means of an enantioselective transaminase. Subsequently, the hydroxyphenylglyoxylates were decarboxylated and then oxidized to 3-and 4-hydroxybenzoate, respectively. These latter compounds in turn were oxidized by NADPH-dependent hydroxylases to protocatechuate, which was further oxidized via an intradiol cleavage. Preliminary experiments with cell extracts in which the 4-hydroxyphenylglyoxylate decarboxylase was partially removed by an ammonium sulfate fractionation showed that D-4-hydroxyphenylglyoxycine could be formed from 4-hydroxyphenylglyoxylate by the enantioselective transaminase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01982906
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  • 10
    Electronic Resource
    Electronic Resource
    Studies on the production of (S)-(+)-solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) by enantioselective oxidation of racemic solketal with Comamonas testosteroni (1994)
    Springer
    Applied microbiology and biotechnology 42 (1994), S. 8-15 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract All strains of Comamonas testosteroni investigated here, produced quinohaemoprotein ethanol dehydrogenase (QH-EDH) when grown on ethanol or butanol, but one strain of C. acidovorans and of C. terrigena did not. Hybridization experiments showed that the gene for QH-EDH is absent in the latter two strains. Induction and properties of the QH-EDHs seem to be similar: all C. testosteroni strains produced the enzyme in its apo-form [without pyrroloquinoline quinone (PQQ)] and the levels were higher at growth at low temperature; preference for the R-enentiomer and similar selectivity was shown in the oxidation of solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) by cells (supplemented with PQQ); the fragment of the qhedh gene gave high hybridization with the DNA of the C. testosteroni strains. Experiments with C. testosteroni LMD 26.36 revealed that the organism is well suited for production of (S)-solketal: it shows an adequate enantioselectivity (E value of 49) for the oxidation of racemic solketal; the conversion rate of (R)-solketal is only 3.5 times lower than that of ethanol; the optimal pH for conversion (7.6) is in a region where solketal has sufficient chemical stability; separation of the remaining (S)-solketal from the acid formed is simple; induction of QH-EDH, the sole enzyme responsible for the oxidation of (R)-solketal, occurs during growth on ethanol or butanol so that the presence of solketal (inhibitory for growth) is not required; production of active cells and the conversion step can be integrated into one process, provided that PQQ and solketal addition occur at the appropriate moment; the conversion seems environmentally feasible. However, since high concentrations of solketal inhibit respiration via QH-EDH, further investigations on the mechanism of inhibition and the stability of the enzyme might be rewarding as it could lead to application of higher substrate concentrations with consequently lower down-stream processing costs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170216
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