Growth and carotenogenesis in Rhodosporidium diobovatum IMB Y-5023: effects of culture medium and illumination intensity.

The oleaginous yeast Rhodosporidium diobovatum is a poorly described producer of carotenoids and may be of interest in biotechnology. This study investigated the effects of culture medium and illumination on effective carotenoid production by R. diobovatum IMB Y-5023. Yeast was cultured on carrot, bran extract, and modified yeast malt (YM) medium at illuminations in the 0-5000 lx range. Biomass, total carotenoids and their profile were assessed after cultivation. In order to compare samples, cluster analysis and principal component analysis were used to visualize the relationships between the variables and samples. Results show that it is not illumination but culture medium that is the main factor determining the quantity and proportions of carotenoids produced by R. diobovatum IMB Y-5023. The yeast grew and produced pigments throughout the tested range of illumination intensity. The modified YM medium was optimal for carotenogenesis. In cultures on that medium, the highest carotenoid yields of 24.98 mg g-1 dry cell weight and 77 mg L-1 were recorded. It was found that this yeast is capable of assimilating oligosaccharides and can grow and produce carotenoids in low-glucose media containing DP3 and DP4. Moreover R. diobovatum IMB Y-5023 produced lycopene as the main pigment independently of the culture conditions.

Resistance to heavy metal toxicity in organisms under chronic exposure.

The rate of changes of heavy metal ions concentrations in the organism or biological system will determine the choice of strategy of realization of heavy metal ions effect and, consequently, the biological effect itself. Which of the possible strategies will dominate, depend on the rate of changes of concentration of heavy metal ions in biological systems, functional activity of organism at the moment of metal action and on metals chemical properties. Keeping this view, the present review deals with the concept of time-based alterations of concentration of heavy metal ions (TACMI) in biological systems. On the basis of TACMI concept formation of organism resistance to metal ions action could be explained. In the event of slow increase of its concentration in organism, it produces induction of metallothioneins, other stress-proteins and relative changes in the whole metabolic system. This, first of all, results in formation of new specific epigenotypes, which provide higher resistance (hormesis effect) not only to metal ions that induced this effect, but also to such stress-factors as high temperature (at least, for micro-algae cells).