Continuous potable alcohol production by immobilizedSaccharomyces cerevisiae on mineral kissiris

A biocatalyst prepared by the immobilization of Saccharomyces cerevisiae on the surface of the mineral kissiris was used in the present study for continuous potable-alcohol production. An ethanol productivity (calculated on the basis of liquid volume) of 10.5 g/L/h was obtained at a 0.7/h dilution rate, 121 g/L sucrose content, and 29.6% conversion employing molasse as feed material. Glucose, raisin extracts, and molasse were successively used as feed materials without stopping the operation of the reactor for 6 mo. The ethanol productivity and yield remained constant during the operational-stability study of the reactor, carried out for 44 d. Biomass productivity, yield, and free-cell concentration in glucose, raisin extracts, and molasse were examined. Finally, a system with two continuous reactors joined successively was also studied in the present investigation.     

Kinetics of ethanol production from carob pods extract by immobilizedSaccharomyces cerevisiae cells

Kinetics of ethanol production from carob pods extract by immobilizedS. cerevisiae cells in static and shake flask fermentation have been investigated. Shake flask fermentation proved to be a better fermentation system for the production of ethanol than static fermentation. The optimum values of ethanol concentration, ethanol productivity, ethanol yield, and fermentation efficiency were obtained at pH range 3.5–6.5 and temperature between 30–35°C. A maximum ethanol concentration (65 g/L), ethanol productivity (8.3 g/Lh), ethanol yield (0.44 g/g), and fermentation efficiency (95%) was achieved at an initial sugar concentration of 200, 150, 100, and 200 g/L, respectively. The highest values of specific ethanol production rate and specific sugar uptake rate were obtained at pH 6.5, temperature 40°C, and initial sugar concentration of 100 g/L. Other kinetic parameters, biomass concentration, biomass yield, and specific biomass production rate were maximum at pH 5.5, temperature 30°C, and initial sugar concentration 150 g/L. Under the same fermentation conditions non-sterilized carob pod extract gave higher ethanol concentration than sterilized medium. In repeated batch fermentations, the immobilizedS. cerevisiae cells in Ca-alginate beads retained their ability to produce ethanol for 5 d.     

Studies on saccharomyces cerevisiae cinder carbon-limiting growth transformed with plasmid pcyg4 that carries the gene for NADP-GDH

The gene (GDH1) coding for the NADP-linked glutamate dehydrogenase system (NADP-GDH) has been cloned fromSaccharomyces cerevisiae strain. Cells being transformed by the NADP-GDH gene on a 2 μm bared vector (pCYG4) plasmid confering 11-fold higher level on expressed GDH activity over the wild-type cells. The behavior of these cells was investigated under chemostatic growth with a carbon ratelimiting nutrient. Specific growth rates of cells carrying plasmid pCYG4 were found to be slightly slower than wild type cells. Furthermore, the NADP-GDH activity increases proportionally with the dilution rate. In addition, oscillations in the NADP-GDH activity, especially at a dilution rate up to 0.15/h, are probably consequential on the appearance of a changing mixed population (cells with and without plasmids).     

Effects of potassium on the ethanol production rate of Saccharomyces cerevisiae carrying the plasmid pCYG4 related with ammonia assimilation

The influence of potassium on ethanol production bySaccharomyces cerevisiae wild type and AR5 cells carrying the plasmid pCYG4 was investigated. This plasmid carries the glutamate dehydrogenase gene conferring an 11-fold higher level of expressed enzyme activity over the wild type cells. All experiments were carried out in batch culture with medium supplemented to different potassium concentrations up to 180 mM. Maximum ethanol production rate was observed in the AR5 cells grown in medium supplemented with 3.5 mM of potassium ions. Glucose uptake rate increased with increasing potassium up to 60 mM, but higher concentrations depressed glucose uptake rate in both strains. Furthermore, the wild type cells showed higher growth rate, ethanol production, and glucose consumption rate than the AR5 cells. These lower rates in the AR5 cells could be explained by repression of potassium uptake by an enhancement of ammonium feeding, and greater energy requirements by these cells due the presence of the plasmid.     

Isolation and enrichment of Ginkgo biloba extract by a continuous chromatography system

In this study, an effective method was developed for the isolation and enrichment of Ginkgo biloba extract by continuous chromatography system. The adsorption and desorption ratio of flavonoids as main index, the best macroporous resin was screened out from six resins by static adsorption and desorption tests. At the same time the adsorption and desorption parameters were optimized by dynamic adsorption and desorption tests. Under optimal parameters, five operations consisting of loading, washing, desorbing, regenerating, and balancing were integrated across the continuous chromatography system for the purpose of refining 66 L of crude extract solution. The results were as follows, 198.22 g of Ginkgo biloba extracts was produced, which contained 65.83 g of flavonoids and 15.44 g of lactones. The content of flavonoids and lactones increased from 2.76 and 0.72% in the crude extract to 33.21 and 7.79%, with a recovery yield of 91.26 and 81.21%. Methodology validation showed that the proposed method had high stability and reproducibility. Compared with the traditional macroporous resin method, the proposed method had a short processing time and low solvent consumption. Our studies indicated that the newly developed method is an effective procedure for the isolation and enrichment of Ginkgo biloba extract.     

Isolation of aromatic compounds from a coal extract by semipreparative HPLC

Summary Two methyldibenzofuran isomers and a tetramethylnaphthalene isomer have been isolated from the organic extract of a Sakoa (southwest Madagascar) coal and were positively identified by IR spectroscopy. The isolation procedures were carried out on a semipreparative scale and included two to four normal-phase HPLC steps and a reversed-phase HPLC step. Reproducibility of the normal-phase fractionations on alumina was enhanced by an improved moisture-control system. Substantial enrichment of the compounds of interest was achieved in each step, as evidenced by capillary GC.     

Effect of a nonmetabolizable analog of fructose-1,6-bisphosphate on glycolysis and ethanol production in strains ofSaccharomyces cerevisiae andEscherichia coli

Fructose-1,6-bisphosphate (F-1,6-P2) is an allosteric activator of two key enzymes of glycolysis: phosphofructokinase and pyruvate kinase. Regulation of glycolysis in a wild-typeSaccharomyces cerevisiae and a recombinantEscherichia coli by a dead-end structural analog of F-1,6-P2 was studied. 2,5-Anhydromannitol (2,5-AM), a structural analog of β-d-fructose, was used. On being taken up by the cells, 2,5-AM was converted into its monophosphate and diphosphate by the enzymes of the glycolytic pathway. The final product, 2,5-anhydromannitol-1,6-bisphosphate, could not be metabolized further and, therefore, accumulated inside the cells. Glucose and fructose were used as substrates. It was found that 2,5-AM at concentrations of 1 mM or less did not have any effect on either substrate consumption or ethanol production. At concentrations of 2,5-AM of 2.5 mM or greater, significant inhibition of both glucose and fructose was observed, with fructose inhibition much more severe. We discuss the possible mechanisms of glycolysis inhibition by 2,5-AM at high concentrations and the regulation of glycolysis by this compound.