Browsing by Subject "Euglena gracilis"

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  • Nieminen, Martta (Helsingfors universitet, 2013)
    The trend of energy policy in European Union as well as in international context has lately been to increase the share of renewable biofuels. The causes for this are global warming, shrinking reserves of fossil fuels and governments' aspiration for energy independence. Microalgae have shown to be a potential source of biofuels. Though cultivation of microalgae has a long history, has production for fuel yet been unprofitable. Production has become more effective as cultivation has shifted from open ponds to controlled photobioreactors but to achieve effective cultivation methods substantially more understanding on the ecophysiology of microalgae is needed. The aim of my thesis was to research the optimal light intensity and temperature of photosynthesis for three microalgae (Chlorella pyrenoidosa, Euglena gracilis and Selenastrum sp.), which are the main parameters limiting the level of photosynthesis in nutrient rich environments such as photobioreactor. The research strains were incubated in eight light intensities (0,15-250 µmol m-2 s-2) and in 5-6 temperatures (10-35 °C). Photosynthetic activity was determined with radiocarbon method which is based on the stoichiometry of photosynthesis. The purpose of radiocarbon method is to estimate how much dissolved carbon dioxide do the algae assimilate when photosynthesizing. In the method the algae are incubated in light and dark bottles where certain amount of radiocarbon (14C) has been added as a tracer. The algae fix 14C in the proportion to available 12C. 14C method has become the most common way to measure the photosynthesis of microalgae. All of the algal strains grew in 10-30 °C but C. pyrenoidosa was the only one which grew also in 35 °C. The data was analyzed by fitting them with two photosynthesis-light intensity relationship models and one photosynthesis-temperature relationship model and as a result values of essential parameters, i.e. optimal light intensity (Iopt) and temperature (Topt) for photosynthesis, could be estimated. The model which gave the best fit was chosen to describe the photosynthesis-light intensity relationship. The optimal light intensity for C. pyrenoidosa ranged between 121–242 µmol m-2 s-2 and optimal temperature was 15 °C. Corresponding values for E. gracilis were 117-161 µmol m-2 s-2 and 24,1 °C, and for Selenastrum sp. 126-175 µmol m-2 s-2 and 16,7 °C. Q10-values were also determined. With all research strains, the level of photosynthesis increased as light intensity and temperature grew until optimal values were reached. The strains tolerated higher light intensities in warmer temperatures but after reaching the optimal temperature, the level of photosynthesis did not increase any more with elevating temperature. Robust algal strains, i.e. strains, that are most adaptable in terms of light intensity and temperature, are the most prominent ones for biofuel production. From these research strains the most adaptable strain in terms of light intensity was C. pyrenoidosa and in terms of temperature Selenastrum sp. C. pyrenoidosa had superior carbon fixation rate in relation to cell size. Therefore it can be concluded that C. pyrenoidosa is the most suitable algal strains for biofuel applications of the strains assessed here.
  • Tossavainen, Marika; Lahti, Katariina; Edelmann, Minnamari; Eskola, Reetta; Lampi, Anna-Maija; Piironen, Vieno; Korvonen, Pasi; Ojala, Anne; Romantschuk, Martin (2019)
    Microalgal cultivation in aquaculture wastewater (AWW) from recirculating aquaculture systems (RAS) is an approach for combined production of valuable algal biomass and AWW treatment. The growth, nutrient uptake, fatty acid (FA) profile, and tocopherol content of mixed algal cultures of Euglena gracilis with Selenastrum grown in AWWs from pikeperch (Sander lucioperca) and catfish (Clarias anguillaris) RAS were studied. The highest algal biomass (1.5gL(-1)), lipid (84.9mgL(-1)), and tocopherol (877.2gL(-1)) yields were achieved in sludge-amended pike perch AWW. Nutrient removal rates in experiments were 98.9-99.5 and 98.4-99.8% for NH4-N and PO4-P, and 75.4-89.2% and 84.3-95.7% for TN and TP, respectively, whereas the COD was reduced by 45.8-67.6%. Biomass EPA and DHA content met, while ARA and tocopherol content exceeded the requirements for fish feed. Algal cultivation in AWWs is a promising alternative for AWW treatment while providing a replacement for fish oil in feed.
  • EFSA Panel Nutr Novel Foods Food; Turck, Dominique; Heinonen, Marina (2020)
    Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the safety of dried whole cell Euglena gracilis as a novel food (NF) pursuant to Regulation (EU) 2015/2283. E. gracilis is a single-cell microalga which occurs widely in nature and is commonly found in freshwater habitats. The NF, the dried biomass of E. gracilis, is produced by fermentation and its major constituent (> 50%) is a beta-glucan polysaccharide. The applicant proposed to use the NF in food supplements, in foods for total diet replacement for weight control and as a food ingredient added to a number of food products. The target population proposed by the applicant is the general population, except for food supplements and for foods for total diet replacement for which the target population is the general population from 12 months of age onwards. In 2019, E. gracilis was attributed the qualified presumption of safety (QPS)-status with the qualification 'for production purposes only, which includes food products based on microbial biomass of the microalga. Based on the information provided, E. gracilis is not expected to survive the manufacturing process. The submitted toxicity studies did not raise safety concerns. No adverse effects were observed in the subchronic toxicity study, up to the highest dose tested, i.e. 3,300 mg NF/kg body weight, considered as the no observed adverse effect level (NOAEL). The margins of exposure between this dose and the high (95th percentile) intake estimates, range from 33 for infants to 192 for adults. The Panel considers that in view of the QPS status of the source of the NF, supported by the compositional data and lack of toxicity observed in the 90-day study, the margins of exposure are sufficient. The Panel considers that the NF, i.e. dried whole cell Euglena gracilis, is safe at the proposed uses and use levels. (C) 2020 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.
  • Amundsen, Mathias Rudolf (Helsingin yliopisto, 2018)
    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.