Abstract. The possibility of using carotenogenic yeast from the genus Rhodotorula as food substrate was studied during the cultivation of Moina macrocopa. The results showed that replacing traditional food substrates during the cultivation of the live fish food M. macrocopa resulted in improved characteristics that were superior to the alternative. Using carotenogenic yeast Rhodotorula glutinis (Fres.) Harrison to stimulate carotenoid accumulation in live feed is better than R. rubra (Demme) Lodder. The optimal duration of enriching M. macrocopa with carotenoids was four days when using various types of yeast capable of carotenogenesis. Replacing the standard medium for culturing M. macrocopa with the alternative medium was less expensive. Breeding live feed on recirculating aquaculture system (RAS) post-production water was proven to be effective.

Abstract. The aim of the study was to determine the impact the commercial supplement S.presso (INVE Aquaculture, Belgium), a source of polyunsaturated fatty acids to enrich the proximate composition of brine shrimp (Artemia sp.), had on their growth and mortality. Four different enrichment protocols were investigated: the supplement was given in one or two doses at various time intervals. The results indicate that while S.presso increased nauplius mortality slightly, administering the appropriate dose reduced losses to a very low level (from 12.5% with a single dose to 8.6% with the recommended dose divided into to equal parts). Additionally, it was confirmed that the supplement S.presso increased brine shrimp growth slightly in comparison to that of the control group, but the differences were statistically insignificant. The results permit concluding that S.presso is suitable for use as a source of polyunsaturated fatty acids for brine shrimp enrichment with the intent of using them as fish food.

Derivatives of 2(5H)-furanone (γ-crotonolactone) are important intermediate synthetic products with a wide range of biological effects that have become widely used in the pharmaceutical industry, medicine, and veterinary medicine, in particular in the prevention and treatment of fish diseases. However, the environmental issue of obtaining these compounds while reducing the negative impact on the surrounding environment remains relevant. This article describes for the first time a method of γ-crotonolactone synthesis that is based on the concept of green chemistry. Synthesis is carried out under mild conditions using nontoxic reagents by furfural oxidation. For the first time, a mixture of hydrogen peroxide and acetic acid was used for the oxidation of furfural in a ratio of 1:0.05. A mixture of organic acids (succinic, maleic, fumaric, formic, and cinnamic acids), obtained as a byproduct in the synthesis of γ-crotonolactone, can be used as a highly effective, ecofriendly organic fertilizer or in a preparation with a stimulating effect.

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Abstract:The nutritional composition and amino acid profile of Moina macrocopa were studied using different types of yeast (Saccharomyces cerevisiae and Rhodotorula glutinis) as fodder substrates. The effective accumulation of carotenoids in Moina macrocopa during R. glutinis yeast application was not accompanied by deterioration in the nutritional value of zooplankton. The content of total proteins and total lipids in Moina grown on S. cerevisiae and R. glutinis was not significantly different. However, the use of R. glutinis in the cultivation of M. macrocopa led to the change in the ratio of proteinogenic amino acids in the studied cladocerans. In particular, the share of methionine, leucine and isoleucine significantly increased. It allowed to enhance the quality of protein in the fodder zooplankton, that is especially important in the feeding of fish fry.

The nutritional composition and amino acid profile of Moina macrocopa were studied using different types of yeast (Saccharomyces cerevisiae and Rhodotorula glutinis) as fodder substrates. The effective accumulation of carotenoids in Moina macrocopa during R. glutinis yeast application was not accompanied by deterioration in the nutritional value of zooplankton. The content of total proteins and total lipids in Moina grown on S. cerevisiae and R. glutinis was not significantly different. However, the use of R. glutinis in the cultivation of M. macrocopa led to the change in the ratio of proteinogenic amino acids in the studied cladocerans. In particular, the share of methionine, leucine and isoleucine significantly increased. It allowed to enhance the quality of protein in the fodder zooplankton, that is especially important in the feeding of fish fry.

This study focused on testing Artemia sp. zooplankton saturation with freshwater microalgae biomass and then using this method to correct the nutritional composition of Artemia. Accordingly, the influence of three species of microalgal monocultures was analyzed (2 freshwater – Desmodesmus armatus (Chod.) Hegew. and Chlorella vulgaris Veijerinck; one halophilous – Dunaliella viridis Teodor.). The algal monocultures were applied once in a quantity of 2-3 × 106 cells × l−1 for each 200,000 Artemia individuals hatched. The control group Artemia did not receive algae. The enrichment process lasted 24 h, and control measurements were performed every 6 h. The survival of Artemia nauplii, their proteolytic activity, and the content of proteins, lipids, and carotenoids were analyzed. The choice of algae species for Artemia enrichment was guided by the size of the algal cells and their biochemical composition. Selected algae contained about 50% protein, 20% lipid, and 12 mg of carotenoids per g of dry weight. Using algae to saturate the Artemia nauplii permitted reducing their mortality during the 24 h enrichment regime. The introduction of C. vulgaris biomass halved this value. The use of algae also increased the proteolytic activity in Artemia nauplii and the content of proteins, lipids, and carotenoids in their biomass. The best results of the bioencapsulation of Artemia nauplii with algae was with the C. vulgaris biomass.

Freshwater zooplankton, which is commonly used as a starting fish feed, has a low content of essential compounds such as carotenoids. The possibility of increasing the productivity of carotenogenic yeast, Rhodotorula glutinis, for further bioencapsulation of zooplankton Daphnia magna is shown. An association of a UV irradiated yeast strain with lactic acid bacteria was cultivated for this purpose. This permitted intensifying the carotenogenesis of yeast, and the content of â-carotene increased by 1.7 times, and that of torularodine by 2.3 times compared with the native monoculture. The use of the association of microorganisms as a feed substrate in the cultivation of Daphnia magna provided both an increase in the carotenoid content in the investigated crustaceans more than 8 times, and their biomass by 2.5 times compared with the standard feed of Saccharomyces cerevisiae.