ANALYSIS OF DAPHNIA MAGNA SURVIVAL CURVES UNDER CONDITIONS OF ENCAPSULATION BY RHODOTORULA MINUTA BIOMASS

Abstract

One of the alternative methods of carotenoid enrichment of feed zooplankton is the use of carotenesynthesizing yeast of the genus Rhodotorula. When their biomass is used as a feed substrate, zooplankton receives a whole range of nutrients along with carotenoids. However, the procedure of bioencapsulation can lead to inhibition of biomass growth and death of zooplankton feeding. It is important to analyze the survival curves of the studied organisms under the conditions of using different concentrations of carotenogenic yeast and to select the optimal enrichment scheme, at which the mortality rate will be the lowest. The aim of this study was to evaluate the possibility of using the yeast Rhodotorula minuta as a feed substrate for Daphnia magna in order to saturate them with carotenoids. The following concentrations of Rhodotorula minuta were used: 1 g/l culture medium (3×1011 CFU/l); 0.5 g/l (1.5×1011 CFU/l); 0.25 g/l (0.75×1011 CFU/l). Saturation of Daphnia magna with carotenoids was carried out for 9 days. The feed substrate of the control group was an aqueous suspension of Saccharomyces cerevisiae yeast. It was found that the use of Rhodotorula minuta as a feed substrate leads to the accumulation of carotenoids in the body of Daphnia magna. The content of total carotenoids in daphnia does not differ statistically when using all studied concentrations of Rhodotorula and is higher by more than 1.5 times compared to the control. The survival rate of Daphnia under the conditions of encapsulation with carotenoid-synthesizing yeast is consistently high. The highest survival rate of daphnia - 92% - was found when using carotene-containing rhodotorula at the lowest concentration of 0.25 g/l, and at a concentration of 1 g/l this figure is almost 40% higher than the values obtained with S. cerevisiae. Keywords: yeast, Rhodotorula minuta, Daphnia magna, survival, carotenoids, live feed