The genes for butanol and acetone formation in Clostridium acetobutylicum ATCC 824 reside on a large plasmid whose loss leads to degeneration of the strain.

Degeneration is the process whereby Clostridium acetobutylicum ATCC 824 loses the capacity to produce acetone and butanol after repeated vegetative transfers or in continuous culture. Two degenerate mutants (M5 and DG1) of C. acetobutylicum ATCC 824 do not contain the four genes (ctfA, ctfB, adc, and aad) for acetone and butanol formation.

Effect of different proteases on bitterness of hemoglobin hydrolysates.

Hemoglobin was hydrolyzed by several enzymes (Proctase, Alcalase, Neutrase, papain). Hydrolysates were analyzed (degree of hydrolysis, gel permeation on Superose 12 column, tasting) and fractionated by ultrafiltration and 2-butanol extraction. The bitter peptides were isolated and identified.

Anaerobic pathways of glycerol dissimilation by Enterobacter agglomerans CNCM 1210: limitations and regulations.

Continuous cultures of Enterobacter agglomerans CNCM 1210 were performed under regulated pH conditions (pH 7.0) with glycerol or glucose (20 g l-1) as carbon source. Cultures grown on glucose produced mainly acetate, ethanol and formate.

Benzoate degradation via the ortho pathway in Alcaligenes eutrophus is perturbed by succinate.

During batch growth of Alcaligenes eutrophus on benzoate-plus-succinate mixtures, substrates were simultaneously metabolized, leading to a higher specific growth rate (mu = 0.56 h-1) than when a single substrate was used (mu = 0.51 h-1 for benzoate alone and 0.

Effects of various types of stress on the metabolism of reserve carbohydrates in Saccharomyces cerevisiae: genetic evidence for a stress-induced recycling of glycogen and trehalose.

It is well known that glycogen and trehalose accumulate in yeast under nutrient starvation or entering into the stationary phase of growth, and that high levels of trehalose are found in heat-shocked cells. However, effects of various types of stress on trehalose, and especially on glycogen, are poorly documented. Taking into account that almost all genes encoding the enzymes involved in the metabolism of these two reserve carbohydrates contain between one and several copies of the stress-responsive element (STRE), an investigation was made of the possibility of a link between the potential transcriptional induction of these genes and the accumulation of glycogen and trehalose under different stress conditions.

Growth of Schizosaccharomyces pombe on glucose-malate mixtures in continuous cell-recycle cultures. Kinetics of substrate utilization.

The aerobic growth of Schizosaccharomyces pombe on mixtures of glucose and malate was investigated during continuous high cell density cultures with partial cell-recycle using a membrane bioreactor. Determination of the specific metabolic rates relative to substrates and products allowed the capacity of the yeast to metabolize malic acid under both oxidative metabolism (carbon limited cultures) and oxidofermentative metabolism (carbon sufficient cultures) situations to be characterized. Under carbon limiting conditions, the specific rate of malate utilization was dependent on the residual concentration and a limit for a purely oxidative breakdown without ethanol formation was observed for a characteristic ratio between the rates of substrate consumption qM/qG of 1.

Cloning and sequencing of a gene coding for a novel dextransucrase from Leuconostoc mesenteroides NRRL B-1299 synthesizing only alpha (1-6) and alpha (1-3) linkages.

The coding region for a Leuconostoc mesenteroides NRRL B-1299 dextransucrase gene (dsrA) was isolated and sequenced. Using a pair of primers designed on the basis of two highly conserved amino-acid (aa) sequences in L. mesenteroides NRRL B-512F dextransucrase and streptococcal glucosyltransferases (GTFs), a fragment of dsrA was amplified by the polymerase chain reaction (PCR).

Modulation of metabolism of Clostridium acetobutylicum grown in chemostat culture in a three-electrode potentiostatic system with methyl viologen as electron carrier.

The metabolism of Clostridium acetobutylicum was manipulated in chemostat culture at pH 5 and 6.5 in a three-electrode potentiostatic system with methyl viologen (MV) as the electron carrier. When a constant potential was applied at pH 5, the broth redox potential continuously decreased and, simultaneously, a high increase in the reduced MV concentration (MV(+.

Flux limitations in the ortho pathway of benzoate degradation of Alcaligenes eutrophus: metabolite overflow and induction of the meta pathway at high substrate concentrations.

The growth behaviour of Alcaligenes eutrophus using various concentrations of benzoate was investigated. In batch culture, growth was exponential and growth rate (mu) and yields (Y) were high [mu = 0.51 h-1 and Yx/benzoate = 0.

In vitro glycosylation of proteins: an enzymatic approach.

The glycosylation pathway is the most important post-translational modification of a protein and is moreover a highly specific process. The majority of proteins of pharmaceutical interest are glycoproteins. Therefore, it is necessary to identify the composition, the structure, the function and the biosynthesis of the glycoproteins.

Effect of temperature and pressure on yeast invertase stability: a kinetic and conformational study.

Kinetics of the temperature- or pressure-induced denaturation of invertase from Saccharomyces cerevisiae were obtained in the temperature range 45-70 degrees C and in the pressure range 500-650 MPa. The investigation was done by measuring the residual activities after cooling or pressure release and the intrinsic fluorescence of aromatic amino-acids (tyrosine and tryptophan) upon excitation at 277 nm. The residual activity decreased exponentially as a function of time incubation according to a biphasic model either with pressure or temperature, whereas the fluorescence emission indicated a difference between these two parameters.

A novel chemoenzymatic glycosylation strategy: application to lysozyme modification.

Hen egg lysozyme has been non-specifically glycosylated using a novel two-step strategy. First, a number of sucrose molecules have been chemically bound to the protein surface lysines, then the glycosidic chains have been enzymically lengthened, using a glycosyltransferase. For this task, a fructosyltransferase and a levansucrase have been tested, the latter appearing as the most effective one.

Genetic and biochemical characterization of the UGP1 gene encoding the UDP-glucose pyrophosphorylase from Saccharomyces cerevisiae.

We report here that the open reading frame YKL248, previously identified during the systematic sequencing of yeast chromosome XI [Purnelle B., Skala, J., Van Dijck, L.

Acetate utilization is inhibited by benzoate in Alcaligenes eutrophus: evidence for transcriptional control of the expression of acoE coding for acetyl coenzyme A synthetase.

During batch growth of Alcaligenes eutrophus on benzoate-acetate mixtures, benzoate was the preferred substrate, with acetate consumption being delayed until the rate of benzoate consumption had diminished. This effect was attributed to a transcriptional control of the synthesis of acetyl coenzyme A (acetyl-CoA) synthetase, an enzyme necessary for the entry of acetate into the central metabolic pathways, rather than to a biochemical modulation of the activity of this enzyme. Analysis of a 2.

Bitter peptide from hemoglobin hydrolysate: isolation and characterization.

Two separation methods, ultrafiltration and 2-butanol extraction, have shown that a peptide is the major agent responsible for bitterness in peptic hemoglobin hydrolysates. It was easily purified from these complex mixtures by specific hydrophobic adsorption on Superose 12, a gel-filtration column, which could constitute an original and interesting method for bitterness detection. The bitter peptide which corresponded to VV-hemorphin 7, the fragment 32-40 of the beta chain of bovine hemoglobin, is first generated during proteolysis, then hydrolysed by pepsin.

Accumulation of trehalose in Saccharomyces cerevisiae growing on maltose is dependent on the TPS1 gene encoding the UDPglucose-linked trehalose synthase.

When yeast strains were cultivated on maltose, the synthesis of trehalose already started in the exponential phase of growth, well before exhaustion of the sugar from the medium. This active pattern of trehalose accumulation was also observed in a maltose constitutive mutant strain growing on glucose. However, this accumulation was completely prevented by deletion of the TPS1 gene coding for the catalytic subunit of the UDPglucose-linked trehalose-6-phosphate synthase, indicating that no alternative pathway for trehalose synthesis exists in yeast.

Regulation of Clostridium acetobutylicum metabolism as revealed by mixed-substrate steady-state continuous cultures: role of NADH/NAD ratio and ATP pool.

Glycerol-glucose-fed (molar ratio of 2) chemostat cultures of Clostridium acetobutylicum were glucose limited but glycerol sufficient and had a high intracellular NADH/NAD ratio (I. Vasconcelos, L. Girbal, and P.

Regulation of carbon and electron flow in Clostridium acetobutylicum grown in chemostat culture at neutral pH on mixtures of glucose and glycerol.

The metabolism of Clostridium acetobutylicum was manipulated, at neutral pH and in chemostat culture, by changing the overall degree of reduction of the substrate, using mixtures of glucose and glycerol. Cultures grown on glucose alone produced only acids, and the intracellular enzymatic pattern indicated the absence of butyraldehyde dehydrogenase activity and very low levels of coenzyme A-transferase, butanol, and ethanol dehydrogenase activities. In contrast, cultures grown on mixtures of glucose and glycerol produced mainly alcohols and low levels of hydrogen.