Maltose metabolism in the yeast Saccharomyces cerevisiae is of great importance both for academic and industrial researchers. It requires the presence of at least one of five independent MAL loci: ...MAL1, MAL2, MAL3, MAL4 and MAL6. Each active locus is made of three genes: two structural genes that encode intracellular enzyme maltase and transport protein for maltose, and the third gene that encodes positive regulatory protein. Maltose is transported unchanged into the cell with the help of specific transmembrane transporter, and then it is hydrolysed by the intracellular maltase into two glucose units which are then channeled through the glycolytic pathway. The maltose metabolism in S. cerevisiae is under the control of three general regulation mechanisms: induction, glucose repression and glucose inactivation. Powerful tools of molecular biology have brought many important discoveries in transport, metabolism and regulation of the uptake of maltose in yeast cells at the molecular level. Although the knowledge on these phenomena is far from being complete, it helps us understand the sugar preference in industrial fermentations on complex substrates but also how glucose effects gene expression and entire metabolic activity in other organisms.
Public urban transit system is of special significance in thetraffic and economic system of big cities. Continuous laggingbehind of the public transit system development compared tothe city ...development can be noticed as a consequence of thetraffic policy and the fascination by the passenger cars. Plannedorientation of the urban traffic systems is of a recent date. Thispaper tends to give incentive to the need for a more complex urbanplanning and planning of traffic in a unique multidisciplinaryprocess within the urban planning system.
Teretna vozila i autocesta Dražen Topolnik; Vladimir Marić
Promet,
10/2012, Letnik:
5, Številka:
3-4
Journal Article
Recenzirano
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Theoretical study has covered the advantages of utilization of highways for traffic of freight vehicles and road toll payment. The conclusion has been drawn that the utilization of highways for ...traffic of heavy vehicles appears indispensable and highly justifiable also in the conditions of road toll payment. In illustration of the structure of the traffic flow on the roads in Croatia, a detailed structure has been shown for the sections of the highway on the Zagreb-Prvča (near Nova Gradiška) route.
In this work, the heterotrophic cultivation of bacterium Paracoccus denitrificans has been studied in a horizontal rotating tubular bioreactor (HRTB). After development of a microbial biofilm on the ...inner surface of the HRTB, conditions for one-step removal of acetate and ammonium ion were created. The effect of bioreactor process parameters medium inflow rate (F) and bioreactor rotation speed (n) on the bioprocess dynamics in the HRTB was studied. Nitrite and nitrogen oxides (NO and N₂O) were detected as intermediates of ammonium ion degradation. The biofilm thickness and the nitrite concentration were gradually reduced with increase of bioreactor rotation speed when the medium inflow rate was in the range of 0.5-1.5 l h-¹. Further increase of inflow rate (2.0-2.5 l h-¹) did not have a significant effect on the biofilm thickness and nitrite concentration along the HRTB. Complete acetate consumption was observed when the inflow rate was in the range of 0.5-1.5 l h-¹ at all bioreactor rotation speeds. Significant pH gradient (cca 1 pH unit) along the HRTB was only observed at the highest inflow rate (2.5 l h-¹). The results have clearly shown that acetate and ammonium ion removal by P. denitificans can be successfully conducted in a HRTB as a one-step process.
Bacterium
Paracoccus denitrificans is capable to obtain metabolic energy by oxidation of ammonia (chemolitotrophic metabolism) and organic compounds (chemoorganotrophic or heterotrophic metabolism). ...It can also perform nitrate and nitrite respiration. When cultivated in certain conditions
P. denitrificans can conduct the complete transformation of ammonia into gaseous nitrogen and consequently the whole nitrogen removal process can be carried out in one step. These characteristics make it suitable for successful treatment of wastewater with high nitrogen content. In this work the heterotrophic cultivation of
P. denitrificans was studied in continuous stirred tank reactor (CSTR) and in horizontal rotating tubular bioreactor (HRTB). Bioprocess dynamics, efficiency and stability in both bioreactors were examined at different dilution rates (
D
=
0.0333–0.1667
h
−1). In both cases, bioprocess dynamics was monitored by the analysis of biomass, substrate and metabolites concentrations in the liqiud outflow. The bioprocess efficiency and stability was much higher in HRTB than in CSTR. Advantages of HRTB over CSTR were more obvious at higher dilution rates as a consequence of bacterial biofilm formation on the inner surface of HRTB that enabled better biomass retention.
Problem of aluminium in beer has been elaborated in several papers over the last decade. However, the effect of aluminium on organoleptic properties of beer has been observed in few papers where it ...has been stated that aluminium gives beer a "metallic" and bitter flavour without any observations on particular aroma compound changes. Also, the number of reports on precise changes of aroma components throughout different storage conditions is surprisingly scarce. In order to investigate the changes of aluminium concentration along with aroma compound changes, graphite furnace-atomic absorption spectrophotometry (GF-AAS) with Zeeman background correction and gas chromatography with static headspace sampler (GC-HSS) were used in this work. Analyses were conducted periodically throughout seven months of storage on three different brands of beer from name breweries. Samples were taken before and after filling in aluminium cans. One part of samples was stored in a refrigerator (4 degree C) and the other in a thermostatic chamber (22 degree C). The effects of beer brand and storage conditions on aluminium concentration and level of aroma compounds were measured. To prove the effect of aluminium concentration on the changes of aroma compounds, the adequate level of aluminium sulphate was added to bottled beer samples stored at 28 degree C. Although different beer types showed significantly different aluminium concentration, it could be the result of other factors (different batches of identical beer type showed significantly different aluminium concentration as well). Samples that were stored in the refrigerator were protected from aluminium migration from the can to the beer and showed increased aroma stability. Level of aroma constituents of analyzed beer brands was significantly different. Elevated aluminium concentration did not have any noticeable effect on the level of aroma compounds in beer samples stored at 28 degree C.
Influence of media composition and temperature on volatile aroma production by various wine yeast strains Petravic Tominac, V.,University of Zagreb (Croatia). Dept. of Biochemical Engineering; Kovacevic Ganic, K.,University of Zagreb (Croatia). Dept. of Food Technology Engineering; Komes, D.,University of Zagreb (Croatia). Dept. of Food Technology Engineering ...
Czech Journal of Food Sciences,
01/2008, Letnik:
26, Številka:
5
Journal Article
Recenzirano
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Volatile aroma compounds production by two autochthonous Saccharomyces cerevisiae strains, isolated from Istria region, and three other yeast strains (Saccharomyces bayanus and two commercial ...Saccharomyces cerevisiae wine yeasts) was investigated on a small scale using synthetic VP4 medium and Grasevina must at 12 and 20 deg C. The results obtained by gas chromatography analyses were compared with the aroma production properties of the native microflora, remaining after Grasevina must sulphiting. In both media and at both temperatures, the wine yeasts investigated showed different metabolic profiles regarding the tested volatile aroma compounds, which should be taken in consideration for autochthonous wine production. Although the synthetic medium proved to be appropriate for the investigation of the fermentative properties, the determination of secondary aroma production by wine yeasts has to be conducted by must fermentation or possibly by fermentation of another synthetic medium whose composition would be more similar to must.
In the present paper, we studied the effect of natural zeolite clinoptilolite on sphingolipid metabolism in the yeast Yarrowia lipolytica. We also investigated if zeolite addition had any impact on ...cell shape and size, as well as on the pH alterations during the culture growth. High performance liquid chromatography analysis of sphingoid bases obtained by acid hydrolysis of complex sphingolipids from Y. lipolytica showed that their concentrations markedly rose upon the zeolite addition. The largest increase among the identified molecular species of sphingoid bases was seen in C18 phytosphingosine, whose levels rose 6.2‐fold and 22.3‐fold after culturing cells for 24 and 36 hours respectively in the presence of finely ground zeolite. pH measurements of the culture medium showed a similarity between pH profiles of control and zeolite‐supplemented cells, suggesting that ion‐exchange capacity was not probably responsible for the observed change in sphingolipid metabolism. Scanning electron microscopy revealed that zeolite affected cell size and shape. Y. lipolytica cells grown in the absence of zeolite were oval‐shaped with an average cell size of 0.7–2.7 μm, whereas when cultured with zeolite, they were round‐shaped and larger, having an average cell size of 1.3–2.9 μm.
The aim of this research was to investigate the effect of growth phase and temperature on the concentrations of the individual molecular species of sphingoid bases obtained by acid hydrolysis of ...total sphingolipids from the yeast Yarrowia lipolytica. Our results showed C18 phytosphingosine to be the major long‐chain base in Y. lipolytica regardless of growth phase or temperature. We also found Y. lipolytica to contain sphingosine, the predominant mammalian long‐chain base that is uncommon for yeast sphingolipids. Among the identified long‐chain bases, only C18 phytosphingosine appeared to be influenced by culture conditions. Its concentration was largest in the exponential phase and decreased 2.9‐fold when cells entered the stationary phase of growth at 28 °C. Following a temperature shift from 28 to 39 °C, there was a 2.1‐fold decrease in the phytosphingosine concentration, but it rose 1.7‐fold after the heat‐stressed cells had been returned to 28 °C and subjected to prolonged growth. These results might point to the possible involvement of phytosphingosine in the cell growth regulation and in the adaptation of Y. lipolytica cells to stressful culture conditions.
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