ГІДРОЛІТИЧНА АКТИВНІСТЬ ТА ПОЖИВНА ЦІННІСТЬ SIMOCEPHALUS VETULUS (MULLER) ПРИ КУЛЬТИВУВАННІ З РІЗНИМИ КОРМОВИМИ СУБСТРАТАМИ

Abstract

The digestive system is characterized by low enzymatic activity at the initial stages of fish larvae development. In this regard, the digestion of fishes during their transition to the external feeding is mostly provided by hydrolytic enzymes of consumed live food, which causes the autolysis. In addition, exogenous hydrolases after their reaching the fish larvae intestine can cause the additional activation of numerous own proteases by limited proteolysis of zymogenes. According to results of previous studies, the possibility of using the carotenogenic yeast Rhodotorula as a source of carotenoids during cultivation of zooplankton as live food for fish larvae was set. However, the impact of mentioned food substrates on the indicators of hydrolytic activity in Cladocera remains unclear. Thus, the purpose of the work was to determine the effect of different food substrates on the hydrolytic activity and nutritional value of live food for fish. The experiment was conducted using pure cultures of S. vetulus (Cladocera). The research organisms were cultivated in a synthetic ADaM medium in climatic chamber conditions. Aqueous suspensions of the yeasts S. cerevisiae , R. glutinis and R. rubra were used as the food substrate for the zooplankton. To enrich live food with carotenoids the zooplankton cultivation was lasted 4 days and yeast introduction were applied every 48 hours. The analysis of carotenoids accumulation showed their maximum content in zooplankton on the 4-th day of cultivation. In this regard, prolonged cultivation of S. vetulus on carotenogenic yeast was appropriate to replace on 4-day passage. The use of R. glutinis and R. rubra yeast as a food substrate even with reduced term of zooplankton cultivation promotes higher content of total proteins in S. vetulus comparing to use of S. cerevisiae . In addition, the application of carotenogenic yeast promotes increasing of lipase and amylase activities in S. vetulus . Using of R. rubra instead S. cerevisiae leads to a slight increase of total proteolytic activity, while applied yeast R. glutinis cause its decline. Consequently, a significant accumulation of carotenoids in S. vetulus already on the 4-th experimental day helps to reduce the time of cultivation of investigated crustaceans on carotenogenic yeast from 28 to 4 days, at the same time the content of main nutrients remains unchanged. The use of Rhodotorula yeast in zooplankton’s diet enhances the lipase and amylase activities in studied organisms and promotes growth of total proteins content. In addition, the use of R. rubra causes a slight increase of the proteolytic activity in S. vetulus .