[Biosynthesis of the non-polyene antibiotic imbricin in the medium containing the producer culture filtrate].

Imbricin (macrolide nonpolyen antibiotic) biosynthesis conditions was investigated in the medium containing culture filtrate of its producer--Streptomyces imbricatus. It was demonstrated that filtrate contains some regulator substance affecting the antibiotic biosynthesis and metabolism processes of actinomycetes S. imbricatus.

[Activity of exoglycans as sorbents of heavy metal ions].

The ability of yeast exoglycans (from Cryptococcus laurentii, Cr. luteolus, and Sporobolomyces albo-rubescens) to absorb copper and lead ions has been studied. The sorption isotherms have been obtained, which indicates that the mechanism of interactions in the system polysaccharide-metal is complex.

[Microbiological synthesis of virazole by immobilized cells].

Based on the isotherms of adsorption of the cells of Xanthomonas campestris B-610 to glass and polyvinyl fibers, immobilized systems were produced, in which the cell content was sufficient for enzymatic synthesis of Virazole (1-[beta-D-ribofuranosyl]-1,2,4-triazole-3-carboxamide) using adenosine as a donor of ribose (50-60% conversion of 1,2,4-triazole-3-carboxamide). The immobilized cells thus obtained retain their enzymatic activity for six months and can be used repeatedly.

[Hydrophobic characteristics of the microorganism cell surface].

Hydrophobic properties of the surface of microorganism cells can be featured by parameters that define the equilibrium of cellular adsorption on liquid carbohydrates: constant of sorption equilibrium, a maximal number of adsorbable cells, as well as coefficient of cellular distribution (Kd) between liquid and organic phases that can be determined either with the equation of adsorption isotherm or experimentally. It is shown that the latter technique gives a more informative characteristics of the hydrophobicity levels in the surface of cells than the percentage of of hydrophobicity cited in literature. The results of this study can be used in the screening of microorganism strains and in the solvation of problems of industrial microbiology related to the fixation of cells on differently structured carriers.

[Effect of several factors on the process of protein solution ultrafiltration].

Ultrafiltration of protein solutions was investigated, using deoxyribonuclease of Actinomyces streptomycini filtered through a membrane based on vinylpyrrolidone-methyl methacrylate copolymers. It was shown that ionization of the protein molecule, level of the applied pressure as well as the protein concentration in the initial solution influenced particle adsorption on the surface and in pores of the molecule and the formation of gel layer reducing the rate of the solution filtration. The following parameters were found to favor the process: pH=7.