L. O. Biliavska, A. M. Ostapchuk, S. I. Voychuk, G. O. Iutynska

Zabolotny Institute of Microbiology and Virology,
National Academy of Sciences of Ukraine, Kyiv;
e-mail: bilyuvskal@gmail.com, galyna.iutynska@gmail.com

The goal of this work was to study biosynthesis of sterols by soil streptomycetes Streptomyces avermitilis IMV Ac-5015, Streptomyces netropsis IMV Ac-5025 and Streptomyces violaceus IMV Ac-5027 on various media under submerged cultivation and to determine their content in bioformulations, developed on the basis of these metabolites producers. Analysis of sterol derivatives extracted from biomass, supernatant of cultural liquid and biological products were performed by GC/MS. The biomass of streptomycetes contained sterols in significantly higher amounts than in the cultural supernatants, and their spectrum and quantitative ratio were different. Squalene – sterol precursor – was found in the biomass in quantities producers 6.2-43.3 μg/g, when streptomycetes grown in synthetic and 8.2-212.1 μg/g in organic media. The biomass of S. avermitilis IMV Ac-5015 was distinguished by domination of 24-epibrassinolide, the content of which was the highest among the tested strains and reached 268.2 μg/g in organic and 345 μg/g in synthetic media. S. avermitilis IMV Ac-5015 did not synthesize sitosterol and stigmasterol that is important in respect of nematicidal properties of the strain. The biomass of S. netropsis IMV Ac-5025 and S. violaceus IMV Ac-5027 grown on organic medium contained 2.3-6.8-fold higher amount of sitosterol and 1.5-3-fold higher amount of stigmasterol compared to synthetic medium. Ergosterol prevailed in sterol spectrum of S. netropsis IMV Ac-5025 and S. violaceus IMV Ac-5027. The highest total content of sterols (9.5 mg/l) was found in Avercom (producer – S. avermitilis ІМV Ас-5015). The use of exogenous sterols of microbial origin is important for regulation of their ratio in plants and for increasing resistance to pathogens and phytonematodes.