Costas Psarianos

Volatile by-products formed in low-temperature wine-making using immobilized yeast cells

Abstract The formation of acetaldehyde, ethyl acetate, propanol-1, isobutanol, amyl alcohols and methanol in repeated batch and continuous fermentations of must using a cryotolerant and alcohol-resistant yeast immobilized on delignified cellulosic material (DCM) and gluten pellets was studied. The fine and fruity aroma of the wines prepared may be attributed to the high content of ethyl acetate in the total volatiles. Immobilization of yeast cells increased ethyl acetate production and, in the case of the DCM, decreased amyl alcohol production at low temperatures compared with free cells. With the DCM-supported biocatalyst, the percentage ethyl acetate of total volatiles minus methanol remained constant as the temperature was reduced, while the amyl alcohol content was reduced. Amyl alcohols are thought to be correlated with improvement of the aroma and the decrease in toxicity of the wine.

Ethanol Production by Saccharomyces cerevisiae Immobilized on Mineral Kissiris

Abstract The attachment of Saccharomyces cerevisiae cells on the cheap and abundant ore Kissiris was investigated. Attached cells produced about 115 g/ l /d ethanol when inoculated in media containing glucose and 96 g/ l /d ethanol in raisin extract. No reduction in ethanol productivity and yield was observed for up to 29 repeated batch fermentations.

New alcohol resistant strains ofSaccharomyces cerevisiae species for potable alcohol production using molasse

Two alcohol resistant strains ofSaccharomyces cerevisiae species were isolated from a Greek vineyard plantation. The strain AXAZ-1 gave a concentration of 17.6% v/v alcohol and AXAZ-2 16.5%, when musts from raisin and sultana grapes, respectively, were employed in alcoholic fermentations. They were found to be more alcohol tolerant and fermentative in the fermentation of molasse than the traditional baker’s yeast. Specifically, using an initial {fx153-1}Be density of 16{fx153-2}Be at the repeated batch fermentation process, in the first as well as fourth batch, the better AXAZ-1 gave final {fx153-3}Be densities of 6.0 and 10.5 respectively, and the baker’s yeast 11.6 and 14.5.

Immobilization of Saccharomyces cerevisiae on γ-alumina pellets and its ethanol production in glucose and raisin extract fermentation

Abstract The immobilization of Saccharomyces cerevisiae cells on γ-alumina pellets was examined by electron microscope and by measurement of the electrokinetic charge of the cells and the γ-alumina pellets. Repeated batch fermentations (about 20) were done for glucose and raisin extract, separately, with an average ethanol production of 80 g/ l ·d and 52 g/ l ·d respectively.

Kissiris: A mineral support for the promotion of ethanol fermentation by Saccharomyces cerevisiae

Abstract Ethanol production using Saccharomyces cerevisiae , promoted by the mineral kissiris, is reported on. A three-fold increase of ethanol productivity in the fermentation of molasses was achieved. An ethanol yield factor 0.43 g/g and conversion of 93.3% at an initial sugar concentration (ISC) 208.5 g/ l were obtained in the presence of this mineral in molasses fermentation, compared to 0.21 g/g and 44.2% in its absence. It is also shown that the fermentation of molasses takes place even at relatively higher ethanol levels, with kissiris contributing to a 35% reduction of the energy demand in grade-fuel and potable ethanol production. The proposed mineral was shown to have a smaller effect in fermentations carried out in synthetic media containing glucose or saccharose.

Continuous potable alcohol production by immobilizedSaccharomyces cerevisiae on mineral kissiris

A biocatalyst prepared by the immobilization ofSaccharomyces 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.

Ethanol fermentation promoted by delignified cellulosic material

Abstract The increase in ethanol productivity by the delignified cellulosic (DC) material, prepared from sawdust after lignin removal, is reported. The DC material increased ethanol productivity by 120%. Final ethanol concentration of 113 ml C2H5OH/l was obtained in the presence of DC material compared with 84 ml C2H5OH/l in its absence when the initial sugar concentration of molasses was 198 g/l.

Tyrosine-4-O-β-glucoside in the mediterranean fruit-fly Ceratitis capitata

Abstract Tyrosine-4-O-β-glucoside was isolated from 5-day-old larvae of Ceratitis capitata, and its structure was established by biochemical and physical techniques. Tyrosine glucoside is the major metabolic product derived from tyrosine during the last larval stage of the fruit-fly.

Alkaline phosphatase in the integument of Ceratitis capitata: developmental profile and functional properties

Abstract Electrophoretic analysis of alkaline phosphatase from the integument during development, reveals two bands of enzyme activity. One corresponding to phosphatase activity during pupation and just prior to eclosion and the other during the middle of the pupal stages. On the contrary in the haemolymph there is one band on enzyme activity through all the developmental stages. The haemolymph alkaline phosphatase band does not comigrate with any integumental enzyme band. The developmental profile of the integumental alkaline phosphatase activity has also been compared to that of the haemolymph. It was found that the pattern of activity is completely different. In the integument, two peaks of enzyme activity were found: one just prior to pupation and the other during eclosion. These two peaks do not coincide to that of haemolymph alkaline phosphatase activity. The pH optimum for both enzyme forms of third instar larvae, although broad especially for haemolymph form, was clearly in the alkaline range, with a peak at pH 8.5–9.0. The two isozymes have different affinities for the substrate tyrosine- O -phosphate. Tyrosine- O -phosphate is the preferred substrate for the integumental enzyme form with a K m of 0.4 mM. We suggest that alkaline phosphates from the integument is specific for the hydrolysis of tyrosine- O -phosphate.

The promotion of molasse alcoholic fermentation usingSaccharomyces cerevisiae in the presence of γ-alumina

Using γ-alumina pellets, more than threefold increase of the ethanol productivity in the fermentation molasse has been obtained in the present work. Also, molasse fermentation in the presence of γ-alumina gave 78.4 g/L ethanol, ethanol yield factor 0.44 g/g, and conversion 89.4% at initial sugar concentration (ISC) 179.5 g/L, compared to 53.9 g/L, 0.30 g/g and 62.7% in its absence, respectively. Furthermore, it was found that γ-alumina reduces the activation energy Ea of fermentation. This inorganic material does not promote the fermentation of raisin extract.