Low silica synthetic faujasite X and synthetic zeolite A formation from sodium-aluminosilicate gels

Synthetic zeolites A and X were prepared from sodium-aluminosilicate gels by crystallization under hydrothermal conditions and at water bath temperature. The process of crystallization and physico-chemical studies on the synthetic zeolites and amorphous aluminosilicate hydrates, from which formed, have been examined by X-ray diffraction measurements, chemical analyses and differential analyses. The structures of synthetic zeolites A and X have been determined in their hydrated form. Zeolite A is represented by the oxide formula : Na2O. Al2O3 . 2 SiO2 . 0.16 NaAlO2 . 4.30 H2O. and the zeolite has the composition (unit cell composition) Na12 [12 AlO2 . 12 SlO2] . NaAlO2 . 29 H2O. The synthetic zeolite X is represented by the oxide formula Na2O . Al2O3 . 2.1 SiO2 (5.63 7.02 ) H2O and the simple zeolite has the composition (unit cell composition) Na94 [94 AlO2 . 94 SiO2] . (260 264) H2O.Des zéolites synthétiques A et X ont été préparées à partir de gels aluminosilicatés sodiques par cristallisation dans des conditions hydrothermales et au bain-marie. Le mécanisme de cristallisation a été examiné et des études physico-chimiques des zéolites de synthèse et des hydrates d'alumino silicates amorphes qui leur ont donné naissance ont été menées par diffraction des rayons X, analyses chimiques et analyses thermiques différentielles. Les structures des zéolites synthétiques A et X ont été déterminées sous leur forme hydratée. La zéolite A est représentée par la formule en oxydes : Na2O. Al2O3 . 2 SiO2 . 0.16 NaAlO2 . 4.30 H2O. et a la composition suivante (en cellule-unité) : Na12 [12 AlO2 . 12 SlO2] . NaAlO2 . 29 H2O. La zéolite de synthèse X est représentée par la formule en oxydes : Na2O . Al2O3 . 2.1 SiO2 (5.63 7.02 ) H2O et à la composition (en cellule-unité) : Na2O. Al2O3 . 2 SiO2 . 0.16 NaAlO2 . 4.30 H2O. and the zeolite has the composition (unit cell composition) Na94 [94 AlO2 . 94 SiO2] . (260 264) H2O.Grba V., Soljic Z. Low silica synthetic faujasite X and synthetic zeolite A formation from sodium-aluminosilicate gels. In: Bulletin du Groupe français des argiles. Tome 27, fascicule 2, 1975. pp. 167-175

Study on the properties of synthetic zeolites A and X and amorphous aluminosilicate hydrates in relation to their application as adsorbents and as thin-layers in the acid medium

Studies on the adsorptive properties of crystalline zeolites and Na-aluminosilicate gels, from which they are formed , show that crystalline zeolites can adsorb molecules of a certain size and shape, but gels cannot. That characteristic of zeolites as adsorbents is unique in orders of adsorbents on the basis of silicates and aluminosilicates. Investigations on the reaction of the amorphous alumino silicate hydrates and crystalline zeolites with diluted acids show that at the beginning an exchange of sodium with H-ions takes place, giving crystalline or amorphous alumino silica te acids. By further treatment a simultaneous transformation of crystalline structure into an amorphous state and decomposition of aluminosilicate acids take place, and finally a complete destruction of aluminosilicate systems occurs.Des études sur les propriétés d'adsorption de zéolites cristallisées et de gels alumino-silicatés sodiques à partir desquels elles se néoforment, montrent que les zéolites cristallisées peuvent adsorber des molécules d'une certaine taille et forme, mais que les gels ne le peuvent pas. Des recherches sur la réaction d'hydrates d'aluminosilicates amorphes et de zéolites cristallisées avec des acides dilués montrent qu'en début de réaction, un échange entre sodium et ions-H se produit, qui donne naissance à des acides d'aluminosilicate cristallisés ou amorphes. Par un traitement plus poussé, on observe une transformation simultanée de la structure cristallisée en une forme amorphe, et la décomposition des acides d'aluminosilicate ; finalement, une destruction complète du système aluminosilicaté se produit.Soljic Z., Grba V. Study on the properties of synthetic zeolites A and X and amorphous aluminosilicate hydrates in relation to their application as adsorbents and as thin-layers in the acid medium. In: Bulletin du Groupe français des argiles. Tome 27, fascicule 2, 1975. pp. 177-183

Incorporation of copper ions by yeast Kluyveromyces marxianus during cultivation on whey

The production of Kluyveromyces marxianus biomass enriched with copper ions were studied. For that reason the growth of Kluyveromyces marxianus in whey with different concentrations of copper ions in batch process under semiaerobic and aerobic conditions were examined. The kinetics of copper ions accumulation in yeast cells, under the same conditions, as well as the reduction of chemical oxygen demand (COD) during yeast growth in aerobic condition, were monitored, as well. The concentration of copper ions in media up to 4 mg l−1 did not affect the yeast growth, whereas at a higher concentration, a marked decrease in the rate of yeast growth, ethanol production and lactose consumption occurred. In semiaerobic conditions, the maximum uptake of 0.35 mg Cu g−1 d.m. was obtained, while in aerobic conditions a lower uptake of 0.26 mg Cu g−1 d.m. and COD reduction of 85% were achieved. COD reduction was independent of the copper addition or uptake

Uptake of iron by yeast cells and its impact on biomass production

Procedures for the production of Saccharomyces cerevisiae biomass enriched with iron and the effects of the iron ions addition into the molasses medium on the yeast growth and the production of ethanol were studied. The growth of the yeast S. cerevisiae and the ethanol production in media with different concentrations of Fe were monitored in the batch process under semiaerobic and anaerobic conditions. The highest biomass concentration and ethanol production were achieved in the medium with 0.6-0.8 g l-1 of Fe under both (semiaerobic and anaerobic) conditions. Kinetics of the iron ions accumulation in yeast cells during 24 h of growth in the batch process under semiaerobic and anaerobic conditions were monitored. In anaerobic conditions the maximum uptake (10 mg g-1 d.m. yeast biomass) was obtained after 12 h of fermentation, while in semiaerobic conditions a four times lower uptake (2.5 mg g-1 d.m. yeast biomass) was obtained after 16 h of fermentation

Enhancement of Trigonopsis variabilis D-Amino Acid Oxidase Overproduction in Fed-batch Cultivation of Escherichia coli

D-Amino acid oxidase is a key enzyme in the production of semisynthetic cephalosporins. The Trigonopsis variabilis D-amino acid oxidase with 12- amino-acid peptide at N-terminus was expressed in Escherichia coli BL21(DE3), in a series of short fed-batch cultivations. The strategy of gradual induction and gradual feeding with D-methionine during expression resulted in active enzyme production twice as high as that in which the inducer and methionine were added all at once at the expression start. In optimal conditions during 14 h of aerobic cultivation, 350 mg L–1 of active enzyme was produced