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Biomedical subjects

A Amrane

Publications and source records attributed to A Amrane.

11 recordsLinked to original sources
PubMed2006

Effect of the dissolved oxygen on the bioproduction of glycerol and ethanol by Hansenula anomala growing under salt stress conditions.

The effect of the dissolved oxygen on glycerol and ethanol productions by an osmotolerant yeast Hansenula anomala was examined during growth in media at low water activity resulting from the addition of 2M NaCl in the culture medium. High stirring rate, high culture medium aeration, as well as high mass transfer surface inhibited both glycerol and ethanol biosynthesis. In absence of oxygen, yeast used acetaldehyde as a hydrogen acceptor, leading to the stimulation of ethanol biosynthesis and accounting for the low biomass and glycerol production; the experimental ratio ethanol on glycerol produced was 5.1 when the available oxygen was lowered (low stirring rate, 500rpm) and increased to 10.2 in absence of aeration. Extracellular glycerol production was therefore optimal for a moderate stirring (1000rpm) and aeration (1.4vvm) rates. These optimal conditions resulted in an experimental ratio ethanol on glycerol produced of 4.1, namely close to the theoretical value of 4, illustrating the osmodependent channelling of carbon towards polyols production.

Biomass↗
PubMed2005

Effect of medium osmolarity on the bioproduction of glycerol and ethanol by Hansenula anomala growing on glucose and ammonium.

The osmotolerant yeast Hansenula anomala survives in media at low water activity resulting from increasing NaCl concentrations in the culture medium by producing compatible solutes. High salinity resulted in the use of a large part of the assimilated carbon substrate (glucose) for cell maintenance (28%), required for intracellular synthesis compounds and for osmotic cell regulation. The maintenance coefficient for non-growth-associated glucose consumption was found to be 0.38 mmol glucose g biomass(-1) h(-1). For decreasing water activity, there is a competition between the pathways leading to glycerol and ethanol production, until an experimental ethanol/total glycerol ratio reached a value 3.4 for 2 mol l(-1) NaCl (close to the theoretical value of 4)-illustrating the osmo-dependent channelling of carbon towards polyols production. This competition leads to a cessation of ethanol production during the stationary state before that of glycerol. Since osmotic adjustment occurred mainly during growth, glycerol production during stationary state can be clearly related to another mechanism other than osmotic: it was excreted by a fermentative mechanism to ensure energy for cell maintenance.

Ethanol↗
PubMed2004

Diffusion of lactate and ammonium in relation to growth of Geotrichum candidum at the surface of solid media.

Geotrichum candidum was cultivated at the surface of solid model media containing peptone to simulate the composition of Camembert cheese. The surface growth of G. candidum induced the diffusion of substrates from the core to the rind and the diffusion of produced metabolites from the rind to the core. In the range of pH measured during G. candidum growth, constant diffusion coefficients were found for lactate and ammonium, 0.4 and 0.8 cm(2) day(-1), respectively, determined in sterile culture medium. Growth kinetics are described using the Verlhust model and both lactate consumption and ammonium production are considered as partially linked to growth. The experimental diffusion gradients of lactate and ammonium recorded during G. candidum growth have been fitted. The diffusion/reaction model was found to match with experimental data until the end of growth, except with regard to ammonium concentration gradients in the presence of lactate in the medium. Indeed, G. candidum preferentially assimilated peptone over lactate as a carbon source, resulting in an almost cessation of ammonium release before the end of growth. On peptone, it was found that the proton transfer did not account for the ammonium concentration gradients. Indeed, amino acids, being positively charged, are involved in the proton transfer at the beginning of growth. This effect can be neglected in the presence of lactate within the medium, and the sum of both lactate consumption and ammonium release gradients corresponded well to the proton transfer gradients, confirming that both components are responsible for the pH increase observed during the ripening of soft Camembert cheese.

Cheese↗
PubMed2002

Reconstruction of the biomass history from carbon and nitrogen substrate consumption, ammonia release and proton transfer during solid cultures of Geotrichum candidum and Penicillium camembertii.

Geotrichum candidumand Penicillium camembertii were cultivated on the surface of a gelified medium, simulating the composition of the aqueous phase of a Camembert cheese. The relation of their growth with substrate consumption (carbon or nitrogen), metabolite production (ammonia), or proton transfer (deduced from pH by means of the buffer capacity of the medium) was examined. The coefficients associated with cellular biosynthesis and resulting from cellular maintenance were determined. From these coefficients and the considered substrate utilization or metabolite production kinetics, the growth kinetics were reconstructed until the end of growth. The model allowed analysis of biosynthesis and cellular maintenance contributions to the considered kinetics. At the end of growth, almost all the peptone was used for G. candidum biosynthesis, while most of the lactic acid (62%) was used for cellular maintenance. P. camembertii metabolized fewer amino acids as carbon sources, resulting in use of peptone for maintenance (12%), and lactic acid (80%) for cell biosynthesis. For both microorganisms, ammonia production was growth-associated, since this production resulted from the deamination of carbon- and nitrogen-source amino acids, in close relation with peptone consumption.

Ammonia↗
PubMed2001

Batch cultures of supplemented whey permeate using Lactobacillus helveticus: unstructured model for biomass formation, substrate consumption and lactic acid production.

The Luedeking and Piret expression can not account for the cessation of production observed at the end of batch; so an empiric term has been previously added to this equation which accounted in a global way for possible substrate limitations. In the model developed in this work, a carbon substrate limitation appeared explicitly in the production expression. Assuming a sigmoidal variation with time of specific growth rate previously validated, the new production model matched well the entire experimental production kinetics. It has been successfully tested for a wide range of nitrogen supplementations, i.e. from an almost total coupling between growth and production for largely supplemented media, to a high decoupling in case of few available nitrogen. Since all the parameters of this model have an obvious biologic meaning, it may be an unvaluable tool for the comprehension of the phenomenon. The model accounted also well for the variation of the specific production rate versus specific growth rate, avoiding the noise due to the direct differentiation of experimental data.

Journal Article↗
PubMed2001

A new model for the reconstruction of biomass history from carbon dioxide emission during batch cultivation of Geotrichum candidum.

A non-structured model has been developed to describe the CO2 emission during growth of Geotrichum candidum on a lactate + peptone-based liquid medium. From the nitrogen and carbon mass balances, it was shown that about 50% of the total CO2 released was from the metabolism of the energy supply for biosynthesis, and the remaining from that for maintenance; thus, CO2 production was considered to be partially associated with growth. The model fitted the experimental data as long as a net growth was observed (0-50 h). The coefficients for growth- and non-growth-associated CO2 production were A = 0.646 (dimensionless) and B = 0.017 h(-1), respectively. From the coefficients of the model and the CO2 history data, the biomass kinetics has been reconstructed, and the calculated biomass concentrations agree fairly well with the experimental data. From this, measurement of the CO2 evolved may be used as an indirect and non-intrusive method of monitoring fungal growth during the first 50 h of cultivation.

Journal Article↗
PubMed1997

Diagnosis of smear-negative pulmonary tuberculosis using sequence capture polymerase chain reaction.

Techniques based on the polymerase chain reaction (PCR) can be used to rapidly identify DNA from Mycobacterium tuberculosis in clinical samples from patients with tuberculosis, but prior studies evaluating this approach in the diagnosis of paucibacillary forms of pulmonary tuberculosis have reported poor sensitivity and/or specificity. We have developed a procedure in which mycobacterial DNA in crude samples is specifically captured prior to amplification, thereby concentrating the target sequences and removing irrelevant DNA and other inhibitors of the amplification reaction (sequence capture PCR). To evaluate the usefulness of this approach in the diagnosis of paucibacillary forms of pulmonary tuberculosis, sequence capture PCR was performed prospectively on samples of bronchoalveolar lavage fluid from consecutive patients suspected of having pulmonary tuberculosis but for whom three consecutive samples of respiratory secretions were smear negative. Of the 27 patients evaluated, active tuberculosis was diagnosed in nine; sequence capture PCR was positive for all of these patients, including the three for whom all specimens submitted for culture were negative. No positive results were obtained for lavage fluid from the 18 patients for whom the diagnosis of active tuberculosis was subsequently excluded or 25 additional patients undergoing bronchoalveolar lavage for evaluation of other pulmonary problems, even though many of these patients had a history of prior tuberculosis or radiographic evidence of prior tuberculous infection. Paucibacillary forms of pulmonary tuberculosis can be rapidly identified with high sensitivity and specificity using sequence capture PCR performed on samples obtained by bronchoalveolar lavage.

Adult↗
PubMed1996

Behaviour of the yeast Kluyveromyces marxianus var. marxianus during its autolysis.

The lactic yeast Kluyveromyces marxianus var.marxianus (formerly K. fragilis) autolyzates at faster rate than Saccharomyces cerevisiae. During K. marxianus autolysis, quite similar release kinetics were observed for intracellular space markers (potassium ions, nucleotides), cell-wall components (polysaccharides, N-acetyl-D-Glucosamine) and non specific products (amino nitrogen). By Scanning Electronic Microscopy examination, no cell burst was observed, but a variation in cell shape (from ellipsoîdal to cylindrical), as well as a 43% decrease in the internal volume were observed. The mechanism proposed for S. cerevisiae autolysis appeared also likely for K. marxianus.

Acetylglucosamine↗
PubMed1990

The efficacy and safety of pefloxacin in the treatment of typhoid fever in Algeria.

The efficacy and safety of pefloxacin 400 mg twice daily for seven days in the treatment of typhoid fever was investigated in an open, non-comparative study involving 37 patients infected with Salmonella typhi. Between day 5 and the end of treatment, all patients showed clinical improvement. The clinical cure rate at the end of the treatment period was 89.2%. One month after the end of treatment, the final assessment showed a clinical cure rate of 94.6% with relapses occurring in only two patients. Both these patients belonged to the group with negative blood cultures but positive serodiagnostic tests. Bacteriological tests confirmed eradication of the pathogen in 94.6% of patients and the relapses in the two serologically positive patients. Temperature became normal in a mean of 5.14 days. Clinical adverse reactions were reported in 5.9% (3/51) of patients (vomiting in two, transient pruritic rash in one). The results of this study indicate that a seven-day course of pefloxacin 400 mg twice daily provides a suitable alternative in the treatment of typhoid fever.

Administration, Oral↗
PubMed1984

[Severe neurological toxicity (coma, convulsions, distal motor neuropathy) secondary to the association of accidental poisoning by isoniazid and a protocol containing high doses of vincristine].

Authors report the case of a 19 year old metastatic Ewing's sarcoma, prophylactically treated for suspected tuberculosis by Rifampicin and INH. Hepatic failure was induced by accidental overdose of INH. A high dose containing VCR protocol associated, lead to a coma with convulsions and severe motor peripheral neuropathy partially regressive. Neurological incidents of VCR, INH and their association are reviewed.

Adult↗