Methanol as a fermentation substrate for the production of phenylalanine, tyrosine and tryptophan by the facultative methylotroph Nocardia sp. 239 (original) (raw)
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Phenylalanine and tyrosine metabolism in the facultative methylotroph Nocardia sp. 239
Archives of Microbiology, 1988
Nocardia sp. 239 is able to use L-tyrosine and both D-and L-phenylalanine as carbon-, energy-and nitrogen sources for growth. The catabolism of these compounds is by way of (4-hydroxy)phenylpyruvate and (4-hydroxy)phenylacetate as intermediates and the pathways merge at the level of homogentisate. The conversion of the amino acids into (4-hydroxy)phenylpyruvate is catalyzed by an inducible NAD-dependent phenylalanine dehydrogenase and L-tyrosine aminotransferase, respectively. Incubation of the organism in media with L-phenylalanine plus phenylpyruvate resulted in diauxic growth, with phenylpyruvate used first. Phenylalanine dehydrogenase activity could only be detected after depletion ofphenylpyruvate, in the ensuing second growth phase on L-phenylalanine. During growth on phenylalanine plus methanol, low levels of phenylalanine dehydrogenase were detected and this resulted in simultaneous utilization of the two substrates. Following diepoxyoctane treatment, mutants of Nocardia sp. 239 affected in phenylalanine and phenylpyruvate degradation were isolated. Double mutants blocked in both phenylalanine dehydrogenase and phenylpyruvate decarboxylase completely failed to catabolize phenylalanine. The absence of these enzymes did not affect growth on tyrosine.
Bioenergetics of methanogenesis from acetate by Methanosarcina barkeri
Journal of Bacteriology, 1988
Methane formation from acetate by resting cells of Methanosarcina barkeri was accompanied by an increase in the intracellular ATP content from 0.9 to 4.0 nmol/mg of protein. Correspondingly, the proton motive force increased to a steady-state level of -120 mV. The transmembrane pH gradient however, was reversed under these conditions and amounted to +20 mV. The addition of the protonophore 3,5,3',4'-tetrachlorosalicylanilide led to a drastic decrease in the proton motive force and in the intracellular ATP content and to an inhibition of methane formation. The ATPase inhibitor N,N'-dicyclohexylcarbodiimide stopped methanogenesis, and the intracellular ATP content decreased. The proton motive force decreased also under these conditions, indicating that the proton motive force could not be generated from acetate without ATP. The overall process of methane formation from acetate was dependent on the presence of sodium ions; upon addition of acetate to cell suspensions of M. ...
Methanol, a potential feedstock for biotechnological processes
1985
Abstract A wide variety of bacteria and yeasts is able to grow in inexpensive synthetic media with methanol as the sole or major source of carbon and energy. This is due to the presence of a few unique enzymes which enable these organisms to generate metabolic energy and synthesize cell constituents from this one-carbon substrate. In the chemical industry there is currently much interest in the production of fuels and chemicals from methanol.
1989
The regulation of aromatic amino acid biosynthesis in Nocardia sp. 239 was studied. In cell-free extracts 3-deoxy-D-arabinoheptulosonate 7-phosphate (DAHP) synthase activity was inhibited in a cumulative manner by tryptophan, phenylalanine and tyrosine. Chorismate mutase was inhibited by both phenylalanine and tyrosine, whereas prephenate dehydratase was very sensitive to inhibition by phenylalanine. Tyrosine was a strong activator of the latter enzyme, whereas anthranilate synthase was inhibited effectively by tryptophan.
Methanogenesis from acetate: Physiology of a thermophilic, acetate-utilizing methanogenic bacterium
FEMS Microbiology Letters, 1985
The physiology is described of a thermophilic acetate-decarboxylating methanogenic bacterium grown with acetate as sole energy and carbon source. The organism had a optimal pH range of 7.3-7.5 and a temperature optimum for methanogenesis near 60°C; no growth occurred above 75°C. Addition of penicillin, D-cycloserine, vancomycin and ampicillin produced no inhibition of methanogenesis at low concentrations 10-100 mg/l). No requirement for growth factors was observed during exponential growth on acetate, but sulfide was found to be necessary for optimal growth. Growth yield was 1.7-2.3 g dry weight per mol of acetate utilized. The apparent K s obtained for methanogenesis from acetate was 0.8 m mol/1. produced from acetate than during digestion at mesophilic temperatures [4,6]. Despite the important role of acetate as a precursor of methanogenesis, few of the methanogens isolated are able to utilize acetate as sole carbon and energy source. The only pure cultures of thermophilic, acetoclastic methanogens described are Methanosarcina TM1 [7] and the TAM organism (Thermophilic Acetate-utilizing Methanogen), a filamentious rod able to utilize H2-CO 2 and formate, as well as acetate [8]. This paper deals with the optimal growth conditions (medium composition, temperature, pH), kinetic data and the effect of antibiotics on growth and methanogenesis of the TAM organism when acetate serves as sole energy and carbon source.
Applied Microbiology and Biotechnology, 2014
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