M. Soupioni

Lead(II) uptake during baker's yeast production by aerobic fermentation of molasses

Lead(II) removal through biosorption on bakers yeast during biomass production was studied to estimate the level of uptake from contaminated molasses medium and to monitor its impact on cell growth. Lead(II) additions had significant negative effects on growth. Concentrations above 50 mgl(-1) resulted in a 50% reduction in growth rate and 60% lower overall biomass yields compared to controls. Nevertheless, the decrease in yeast biomass did not lead to decreased lead(II) uptake, on the contrary the biosorption ability was higher at higher initial lead(II) concentrations

Effect of freeze-dried immobilized cells on delignified cellulosic material in low-temperature and ambient-temperature wine making.

In this article, were port on wine making by freeze-dried immobilized cells on delignified cellulosic material for ambient and low temperatures. Biocatalyst supported by freeze-dried delignified cellulosic (FDC) material recovered after the first repeated-batch fermentations the fermentation efficiency and startup, which become about equal to those of biocatalyst supported by wet delignified cellulosic material. The FDC biocatalyst was suitable for wine making at low temperatures (5–15°C), and produced wine of 12% alcoholic degree, with the main volatiles contained in the wine and reduced by a decrease in temperature. The fermentation efficiency was not affected by total acidity of must, while an increase in initial Be density improved percentages of higher alcohols and ethylacetate. The quality of the wine was validated by a preliminary taste test to be in the range of acceptable to excellent.

Research perspectives and role of lactose uptake rate revealed by its study using 14C-labelled lactose in whey fermentation.

The present investigation examines the effect of pH, temperature and cell concentration on lactose uptake rate, in relation with kinetics of whey fermentation using kefir and determines the optimum conditions of these parameters. Lactose uptake rate was measured by adding (14)C-labelled lactose in whey. The results reveal the role of lactose uptake rate, being the main factor that affects the rate of fermentation, in contrast to the activity of the enzymes involved in lactose bioconversion process. Lactose uptake rate results discussion showed that mainly Ca(2+) is responsible for the reduced whey fermentation rate in comparison with fermentations using synthetic media containing lactose. Likewise, the results draw up perspectives on whey fermentation research to improve whey fermentation rate. Those perspectives are research to remove Ca(2+) from whey, the use of nano and microtubular biopolymers and promoters such as γ-alumina pellets and volcan foaming rock kissiris in order to accelerate whey fermentation.

Effect of temperature on the formation of volatile by‐products in brewing by immobilized cells

Abstract The formation of acetaldehyde, ethyl acetate, propanol‐1, isobutanol, amyl alcohols and methanol in repeated batch fermentations and continuous fermentations of wort, performed by a cryotolerant and alcohol resistant strain of Saccharomyces cerevisiae species, immobilized on delignified cellulosic (D.C.) material and gluten pellets was studied mainly at low temperatures. It was found that the fine and fruity aroma of beers obtained at lower temperatures may be attributed mainly to increase of % ethyl acetate on total volatiles determined and to decrease of amyl alcohols. D.C. material resulted to lower contents of higher alcohols in batch and continuous brewing as compared with gluten and free cells principally at low temperatures. Amyl alcohols and other higher alcohols were reduced in all cases (immobilized and free cells) as the temperature was decreased. Same change of amyl alcohols and other higher alcohols is reported in the case of gluten pellets as the temperature was reduced. However, th...

Study of whey fermentation by kefir immobilized on low cost supports using 14C-labelled lactose

Brewers Spent Grains (BSG) and Malt Spent Rootlets (MSR) were used as supports for kefir cells immobilization and the role of lactose uptake rate by kefir in the positive activity of produced biocatalysts during whey fermentation was investigated. Lactose uptake rate by the immobilized cells was recorded using (14)C-labelled lactose and the effect of various conditions (pH, temperature and kind of support) on it and consequently on fermentation time and ethanol production was examined. The results showed that lactose uptake rate was correlated to fermentation rate and increased as temperature was increased up to 30°C at pH 5.5. The same results have been recently noticed by using biocatalysts with Delignified Cellulosic Materials (DCM) and Gluten Pellets (GP), but fermentation time of about 7h by kefir immobilized on DCM and BSG resulted to two fold lower than that on GP and MSR. The highest alcohol concentration was observed by MSR.

OSCILLATORY TRANSFER ANNEALING IN RADIODOPED CHEMICAL COMPOUNDS

Doping of crystalline /CoEDTA/2 Ba and /Co(en)3/(NO3)3 by60Co2+ creates a thermodynamically dissipative structure which gives rise to an oscillatory exchange of the radiocobalt with the inactive Co/III/ of the complex ions. The same compounds in which energetic60Co atoms have been produced by neutron irradiation show kinetically the same oscillatory parameters. The Volterra-Lotka model is applied for the oscillations.

Lactose uptake rate by kefir yeast using 14C-labelled lactose to explain kinetic aspects in its fermentation.

Tauhe present work shows the relation between kefir fermentation ability and carbohydrate uptake rate. This was examined in a model system containing kefir co-culture and lactose in order to study fermentation induced by yeasts and bacteria at the same time. Lactose uptake rate was recorded by using (14)C-labelled lactose. The effect of lactose, cell concentration and pH on lactose fermentation was examined. Results have shown increase of lactose uptake rate at lower cell concentrations and specifically the maximum values of lactose uptake rate were obtained at 30 degrees C, 5.5 pH value and initial lactose and cell concentration 10% w/v and 16 g/L, respectively. Likewise, lighten that the increase of the fermentation rate by immobilized cells can be attributed also, in addition to other factors, to lower cell concentration on the surface of the support or of the promoter. Besides, it is shown that the effect of pH value on the biochemical reactions, carried out by intracellular enzymes can be attributed, except to the effect of pH on enzyme ability, in addition to the effect of pH on carbohydrate uptake rate.

Lactose uptake rate measurements by 14C-labelled lactose reveals promotional activity of porous cellulose in whey fermentation by kefir yeast

Lactose uptake rate by kefir yeast, immobilized on tubular cellulose and gluten pellets during fermentation of lactose and whey, was monitored using (14)C-labelled lactose. Results illustrated that, in all cases, lactose uptake rate was strongly correlated with fermentation rate and the fermentations kinetic parameters were improved by kefir yeast entrapped in tubular cellulose. As a result, twofold faster fermentations were achieved in comparison with kefir yeast immobilized on gluten. This is probably due to cluster and hydrogen bonds formation between cellulose and inhibitors, such as Ca(++) and generated lactic acid, by which they leave the liquid medium. The findings, regarding the promotional effect of cellulose, seem promising for application in industrial whey fermentations.

Neodymium sorption by clay minerals and zeoliferous rocks

The sorption of neodymium from its aqueous solutions (concentration range approx. 10–450 mg l−1) by montmorillonite, kaolinite and a clinoptilolite-containing rock has been investigated, using147Nd as radioactive tracer and γ-ray spectrometry. The neodymium uptake by montmorillonite was found to be much higher than of the other two materials in the whole investigated concentration range. However, in the case of montmorillonite and zeoliferous rock, the uptake ability is lower than that allowed by the measured CEC values and can be described by Langmuir-type equations. In the case of kaolinite, the observed higher than CEC-allowed uptake values could be attributed to sorption by mechanisms other than ion-exchange. The corresponding data obey a Freundlich-type sorption equation. Among the three geological materials investigated, montmorillonite exhibits the highest perspectives of application for the treatment and disposal of neodymium and trivalent actinides in nuclear industry.

Exploration for longer periods in the oscillatory annealing phenomenon in neutron irradiated crystalline cobaltic compounds

The oscillatory phenomenon during isothermal annealing of neutron irradiated crystalline cobaltic complexes is shown to extend for heating times up to 120 h without significant damping of amplitude and frequency of the oscillations. A mechanistic approach based on the Volterra-Lotka model is attempted involving defects and dissipative structure according to non-equilibrium thermodynamics.