Biomedical subjects

A Latrasse

Publications and source records attributed to A Latrasse.

4 recordsLinked to original sources

PubMed1999

In situ detoxification of the fermentation medium during gamma-decalactone production with the yeast sporidiobolus salmonicolor

gamma-Decalactone (gamma-C10) is known to be highly toxic for the microorganims used for its production. In this work, three techniques were studied in order to overcome this toxicity during a bioconversion process using ricinoleic acid as precursor of the lactone: in situ trapping in oily phases, in porous hydrophobic sorbents and in beta-cyclodextrins. Oily phases added to the media (olive, Miglyol, tributyrin, and paraffin) had a protective effect on Sp. salmonicolor, and they improved the lactone production. beta-cyclodextrins, which have a hydrophobic cavity that can trap molecules such as gamma-C10, have been used to protect the yeasts. The results showed insufficient preservation of cell viability. Some sorbents (activated carbon and polystyrene-based sorbents) were successfully tested during bioconversion. In all cases viability exceeded the reference one. Nevertheless the aroma production was 30% lower than the reference. All of these solutions led to some enhancement of the cell viability during bioconversion of methyl ricinoleate to gamma-C10. For improvement of the lactone production, the oil trapping method seemed to be the best with the experimental conditions tested.

Journal Article↗

PubMed1997

Chirality of the gamma-lactones produced by Sporidiobolus salmonicolor grown in two different media.

Sporidiobolus salmonicolor is an aroma-producing yeast which gives a peach-like smell to the culture media. The enantiomeric ratios of the five gamma-lactones produced by this yeast cultivated in two different media were determined by multidimensional gas chromatography (MDGC) on a fused silica capillary column coupled to a modified beta-cyclodextrin column. These ratios remain constant during growth and are not affected by the composition of the medium. The (R)-enantiomer is highly predominant (99%) for gamma-decalactone and predominant (68-88%) for gamma-octalactone, gamma-nonalactone, and (Z6)-gamma-dodecenolactone. A ratio close to racemic was found for gamma-dodecalactone. A discussion on the metabolic origin of these lactones is based on the analysis of the enantiomeric ratios obtained. With respect to consumers' preference for products considered as "natural," microbial lactone production may represent a valuable alternative to fruit flavors. The enantiomeric lactone ratios produced by Sporidiobolus salmonicolor are compared with those reported from some fruits.

Basidiomycota↗

PubMed1993

Chirality of the gamma-lactones formed by Fusarium poae INRA 45.

A filamentous fungus, Fusarium poae INRA 45, was grown in two liquid Czapek-type media (a Czapek medium, and a yeast extract plus casaminoacids-enriched Czapek medium). Eight gamma-lactones, i.e., gamma-penta-, gamma-octa-, gamma-nona-, gamma-deca-, and gamma-dodecalactone, (6Z)-gamma- and (6E)-gamma-dodecenolactones, and a di-unsaturated gamma-dodecalactone, were tentatively, or conclusively, identified by capillary gas chromatography (GC) and coupled GC-MS, in the volatile fractions of the cultures. Kinetics of the formation of gamma-dodecalactone, (6Z)-gamma- and (6E)-gamma-dodecenolactones, (three major lactones), and gamma-dodecalactone (a minor lactone) were quantitatively studied by computerized GC integration. Variations of the (R/S) ratios of the lactone enantiomers were quantitatively studied by computerized multidimensional gas chromatography (MDGC) integration. The levels of the lactones were superior in the enriched Czapek-type medium to those of the Czapek medium, but the compositions of these media did not influence significantly the (R/S) ratios of these lactones. Formation of the enantiomers is discussed in terms of metabolism of potential precursors.

Chromatography, Gas↗

PubMed1978

[Proteo-polysaccharidic turbidity in depectinized raspberry juice].

A revertible turbidity happens in the depectinized red raspberry juice under refrigeration. Its analysis is carried out: --Chemically: Total sugar determination by anthrone methol, galacturonic acid determination by carbazol, total nitrogen determination according to Berthelot's coloured reaction (automated analysis) -- Physically: Calcium, potassium and magnesium determinations by atomic absorption. -- Chromatographically: Sugar separation and determination by HPLC. M. W. determination of the different entites by GPC (gel Sephadex G 100). Pectic substances separation on DEAE-cellulose column. The turbidity ensues from an enhanced by cold and acidic pH flocculation process which occurs between the large nitrogeneous molecules (inactive and enzymic proteins mainly). M. W. (superior to 150.000) of the depectinizing preparation and rich in glucose and mannose polysaccharidiques (M. W. between the range from 1.000 to 10.000) accompanied by aldobiuronic units. The origin of the manno-glucan entity remains to be determined. It could be issued either a limit-substrate produced by the degradation of the raspberry pectic substances or an by Aspergillus niger excreted compound.

Beverages↗