Slavica B. Ilić

Spectroscopic and thermodynamic studies of complexation of some divalent metal ions with isatin-β-thiosemicarbazone

Metal complexes of some divalent metal ions (Co, Ni, Cu, Zn, Hg, and Pd) with isatin-β-thiosemicarbazone (ITS) as the Schiff base have been investigated potentiometrically and spectrophotometrically. The dissociation constants of the ligand and formation constants of the metal complexes, as well as the corresponding thermodynamic functions (ΔG, ΔH and ΔS) have been determined at different temperatures in ethanol—water solution. The full stability constants were also evaluated spectrophotometrically by the Job method. The experimental results indicate that Cu(II), Zn(II), Pd(II), and Hg(II) form one-to-one molecular complexes (ML) with the studied ligand, whereas Co(II) and Ni(II) form both ML and ML2 species.

The Influence of Modified Media with Carboxymethyl Cellulose on Morphology and Antibiotic Production by Streptomyces Hygroscopicus

ABSTRACT Actinomycetes, especially members of the genus Streptomyces, are responsible for producing the majority of known antibiotics. The production of antibiotics by filamentous organisms is often dependent on the morphology and size distribution of the pellet population within the culture. The effect of carboxymethylcellulose (CMC) on growth and antibiotic (hexaene and azalomycine) production by Strepotmyces hygroscopicus were investigated. By adding the polymer to the fermentation medium, the growth was changed from a single large glob to small reproducible pellets, and wall growth was diminished to a minimum. Maximum concentration of hexaene was reached at 3% (wt/vol) CMC and maximum concentration of azalomycine was reached at 1 % (wt/vol) CMC.