Biomedical subjects

James Gomes

Publications and source records attributed to James Gomes.

4 recordsLinked to original sources

PubMed2005

Effect of cysteine on methionine production by a regulatory mutant of Corynebacterium lilium.

The production of methionine by submerged fermentation using a mutant strain of Corynebacterium lilium was studied to determine suitable conditions for obtaining high productivity. The mutant strain resistant to the methionine analogues ethionine, norleucine, methionine sulfoxide and methionine methylsulfonium chloride produced 2.34 g l(-1) of methionine in minimal medium containing glucose as carbon source. The effect of cysteine on methionine production in a 15 l bioreactor was studied by supplementing cysteine intermittently during the course of fermentation. The addition of cysteine (0.75 g l(-1)h(-1)) every 2 h to the production medium increased the production of methionine to 3.39 g l(-1). A metabolic flux analysis showed that during cysteine supplementation the ATP consumption reduced by 20%. It also showed that the increase in flux from phosphoenol pyruvate to oxaloacetate leads to higher methionine production. Results indicate that controlling the respiratory quotient close to 0.75 will produce the highest amount of methionine and that regulatory mutants also resistant to analogues of cysteine would be better methionine over producers.

Adenosine Triphosphate↗

PubMed2005

Methionine production by fermentation.

Fermentation processes have been developed for producing most of the essential amino acids. Methionine is one exception. Although microbial production of methionine has been attempted, no commercial bioproduction exists. Here, we discuss the prospects of producing methionine by fermentation. A detailed account is given of methionine biosynthesis and its regulation in some potential producer microorganisms. Problems associated with isolation of methionine overproducing strains are discussed. Approaches to selecting microorganism having relaxed and complex regulatory control mechanisms for methionine biosynthesis are examined. The importance of fermentation media composition and culture conditions for methionine production is assessed and methods for recovering methionine from fermentation broth are considered.

Corynebacterium↗

PubMed2004

Cascade of bioreactors in series for conversion of 3-phospho-D-glycerate into D-ribulose-1,5-bisphosphate: kinetic parameters of enzymes and operation variables.

A novel scheme employing enzymatic catalysts is described enabling conversion of D-ribulose-1,5-bisphosphate (RuBP) from 3-phospho-D-glycerate (3-PGA) without loss of carbon. Bioreactors harboring immobilized enzymes namely, phosphoglycerate kinase (PGK), glycerate phosphate dehydrogenase, triose phosphate isomerase (TIM), aldolase, transketolase (TKL), phosphatase (PTASE/FP), epimerase (EMR) and phosphoribulokinase (PRK), in accordance with this novel scheme were employed. These reactors were designed and constructed based on simulations carried out to study their performance under various operational conditions and allowed production of about 56 +/- 3% RuBP from 3-PGA. This method of synthesis of RuBP from 3-PGA employing immobilized enzyme bioreactors may be used for continuous regeneration of RuBP in biocatalytic carbon dioxide fixation processes from emissions where RuBP acts as acceptor of carbon dioxide to produce 3-PGA, rendering the fixation process continuous.

Bioreactors↗

PubMed2002

Effect of seed culture on solid-state bioconversion of wheat straw by Phanerochaete chrysosporium for animal feed production.

The solid-state bioconversion of wheat straw by Phanerochaete chrysosporium for the production of animal feed was studied. This study was performed based on a central composite experimental design. The conditions of the seed culture most suitable for rapid induction of the ligninolytic activity of the fungus, when the seed culture is subsequently used for solid-state bioconversion of wheat straw, were determined. When the seed culture with an initial pH of 5.8 was grown under agitated conditions at 130 rpm in baffled flasks at 38 degrees C, it was predicted to give lignin degradation of 19.5% and cellulose degradation of 17.8%. A time profile study of the solid-state bioconversion of wheat straw indicated that the highest lignin and lowest cellulose degradation levels occurred on the sixth day of cultivation. The desirability coefficient for this process also passed through a maximum of 0.705 on the sixth day.

Journal Article↗