Study of carbohydrates in Euglena gracilis

The literature review deals with the basics of microalgae, microalgal cultivation and harvest, and the organism Euglena gracilis. The carbohydrates found in E. gracilis are discussed, with the focus on the storage carbohydrate paramylon. The review also deals with effects of cultivation conditions on composition of microalgae. The aim of the experimental work was to investigate carbohydrate composition in E. gracilis, and in this way increase the knowledge of the microalgae. E. gracilis cultivated in five different environments was studied for content of the beta-glucan paramylon, as well as free sugars and oligosaccharides. As the method used for determination of paramylon content was a gravimetric method, a glucose measurement, protein determination and size-exclusion chromatography were performed on the paramylon isolated. In addition, the effect of supercritical fluid extraction (SFE) of the biomass to extract high value compounds on the overall carbohydrate composition and content was also investigated. In addition, the SFE samples were also analysed according to the AOAC method for dietary fibre The paramylon content in the E. gracilis biomass was between 22 and 40 % of the dry biomass. SEC analysis of this paramylon isolated showed that it was of molecular weight around 150 kDa, but that it was not only paramylon that had been isolated, but the isolates also contained impurities. This was also confirmed by the analysis of glucose and protein in the isolates. Possible compounds that can have been isolated with the paramylon are leftover peptides bound to the tight paramylon structure, chlorophyll, or glycoproteins. The most abundant sugars found in E. gracilis biomass were mannitol, trehalose and glucose, with a total content of and the total content of the samples were from between 2.4 and 14.9 % of the E. gracilis of the total dry mass. There were also some other unquantified free sugars, such as lactose seen in the E. gracilis biomass. The oligosaccharide content was considered low and not further quantified.