Protatrans as biomodulators of <i>Candida ethanolica</i> growth

Abstract

This study was aimed at investigating compounds from a series of protatranes as biostimulants for the growth of the Candida ethanolica yeast. The relevance of the study is associated with the need to determine conditions accelerating the growth of microorganisms in the presence of such highly effective, physiologically active and non-toxic compounds as protatranes. The research object was the Candida ethanolica yeast cultivated on a synthetic nutrient medium containing 1.5% ethanol solution as a carbon source. Protatrans were used at concentrations of 1·10-6 – 1·10-8 wt%. The number of yeast cells was controlled by determining the optical density of yeast suspensions using a KFK-3 Zomax photoelectrocolorimeter at a wavelength of 540 nm and optical path length of 10 mm. The determination of yeast biomass was carried out gravimetrically. The first stage of the work set out to study the accumulation of cells and biomass at various initial yeast cell concentrations. It was revealed that a slight increase in the initial concentration of yeast cells leads to a noticeable shift of the entire S-curve to the left. A comparison of the obtained data sets showed that the investigated protatranes significantly increase the specific growth rate and reduce the generation time during the log phase, provided that this phase accounts for a significant part of the cultivation process. However, the presence of protatranes significantly reduce the specific growth rate and increase the generation period in the log phase, provided that the culture remains in the stationary phase for a significant part of the cultivation time. This is likely to be associated with the positive effect of protatranes on protein synthesis, which is most intense during the log phase. The use of protatranes facilitates the control over the number of cells, amount of biomass, specific growth rate and generation time of the Candida ethanolica yeast depending on the initial cell concentration and, accordingly, the growth phase of the culture.