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In this research heterotrophic cultivation of photosynthetic protist Euglena gracilis was carried out on synthetic (Hutner medium) and complex cultivation media in order to produce -1, 3-glucan (paramylon). For preparation of complex media various industrial by-products (e.g. molasses, corn steep solid, yeast and beef extract) with or without addition of pure compounds [glucose, galactose, fructose, lactose, maltose, sucrose and (NH4)2HPO4] were used. Heterotrophic cultivation of E. gracilis was performed in Erlenmeyer flasks and additionally confirmed during research in the stirred tank bioreactor. The results of this research clearly show that E. gracilis could easily metabolize glucose and fructose (compared to other sugars used in this research) as carbon sources and corn steep solid as complex nitrogen and growth factors source for biomass growth and paramylon synthesis during cultivation in heterotrophic conditions. Furthermore, it was also proved that addition of (NH4)2HPO4 (source of nitrogen and phosphorus), beef extract (source of nitrogen compounds and vitamin B12) or gibberellic acid (plant growth hormone) did not have significant impact on the biomass growth and paramylon synthesis. After optimization of complex medium composition and verification of these results during E. gracilis cultivations in the stirred tank bioreactor it was concluded that medium composed of glucose (20 g/L) and corn steep solid (25 g/L) is the most suitable complex cultivation medium for industrial production of paramylon.

Unicellular algae Euglena gracilis is one of the most interesting organism for industrial production of beta-1, 3-glucan (paramylon). In heterotrophic conditions, E. gracilis has capability to accumulate intracellularly large amounts of paramylon. Therefore, it could be used as an alternative source of b-glucan to Saccharomyces cerevisiae, currently industrially exploited for its extraction. Paramylon (as a linear polysaccharide) has positive effect on human health and it is mostly used in medicine as an immunostimulant and immunopotentiator. The aim of this research was to enhance yield of Euglena gracilis biomass and paramylon by cultivating cells in synthetic and complex [containing different components such as potato liquor, concentrated potato liquor, molasses, corn steep solid, yeast extract etc.] media and to improve the recovery of paramylon. In this investigation comparison between different cultivation techniques (batch, fed batch and repeated batch) was also done. During this research following cultivation parameters were monitored: biomass dry weight, cell number, sugar and paramylon concentrations, dry metter of medium, C and N content of medium. On the basis of obtained results it can be concluded that complex medium with potato liquor is the most adequate medium for E. gracilis cultivation. In this research, paramylon content in dry biomass was up to 80 %. Repeated batch technique is the most adequate cultivation technique for industrial paramylon production because of the highest obtained yields and productivities during these cultivations. In this investigation, successful procedure for paramylon isolation and purification was also established.

beta-1, 3-glucan as a linear polysaccharide has positive effect on human health and it is mostly used in medicine as a immunostimulant and immunopotentiator. Euglena gracilis has capability to accumulate large amounts of intracellular beta-1, 3-glucan (paramylon) when it grows in heterotrophic conditions. Therefore, it could be used as an alternative source of beta-glucan to Saccharomyces cerevisiae, currently industrially exploited for its extraction. The aim of this work was to enhance yield of Euglena gracilis biomass and paramylon by cultivating cells in complex medium [containing different components such as molassess, corn steep solid (CSS), yeast extract etc.] and to improve the recovery of paramylon. In this work, E. gracilis was cultivated at 28 ^oC for 5 days on rotary shaker (120 rpm). Medium was prepared by combination of molasses in the range of 20 - 75 g/L and CSS or yeast extract in the range of 10 - 50 g/L. During this research following cultivation parameters were monitored: biomass dry weight, cell number, sucrose and paramylon concentrations. On the basis of obtained results it can be concluded that medium with 30 g/L molasses and 30 g/L CSS is the most adequate medium for E. gracilis cultivation.