Browsing by Subject "microalgae"

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  • Peltomaa, Elina; Hällfors, Heidi; Taipale, Sami J. (2019)
    Recent studies have clearly shown the importance of omega-3 (-3) and omega-6 (-6) polyunsaturated fatty acids (PUFAs) for human and animal health. The long-chain eicosapentaenoic acid (EPA; 20:5-3) and docosahexaenoic acid (DHA; 22:6-3) are especially recognized for their nutritional value, and ability to alleviate many diseases in humans. So far, fish oil has been the main human source of EPA and DHA, but alternative sources are needed to satisfy the growing need for them. Therefore, we compared a fatty acid profile and content of 10 diatoms and seven dinoflagellates originating from marine, brackish and freshwater habitats. These two phytoplankton groups were chosen since they are excellent producers of EPA and DHA in aquatic food webs. Multivariate analysis revealed that, whereas the phytoplankton group (46%) explained most of the differences in the fatty acid profiles, habitat (31%) together with phytoplankton group (24%) explained differences in the fatty acid contents. In both diatoms and dinoflagellates, the total fatty acid concentrations and the -3 and -6 PUFAs were markedly higher in freshwater than in brackish or marine strains. Our results show that, even though the fatty acid profiles are genetically ordered, the fatty acid contents may vary greatly by habitat and affect the -3 and -6 availability in food webs.
  • Salmi, Pauliina; Mäki, Anita; Mikkonen, Anu; Pupponen, Veli-Mikko; Vuorio, Kristiina; Tiirola, Marja (Suomen ympäristökeskus, 2021)
    Boreal Environment Research 26: 17-27
    The smaller the phytoplankton, the greater effort is required to distinguish individual cells by optics-based methods. Flow cytometry is widely applied in marine picophytoplankton research, but in freshwater research its role has remained minor. We compared epifluorescence microscopy and flow cytometry in assessing the composition, abundance and cell sizes of autofluorescent picophytoplankton in epilimnia of 46 Finnish lakes. Phycocyaninrich picocyanobacteria were the most dominant. The two methods yielded comparable total picophytoplankton abundances, but the determination of cell sizes, and thus total biomasses, were on average an order of magnitude higher in the microscopy results. However, flow cytometry yielded higher cell sizes when applied on small-celled cultured algae. Our study demonstrated that both epifluorescence microscopy and flow cytometry are useful methods in assessing abundances of phycocyanin-rich and phycoerythrin-rich picocyanobacteria and eukaryotic picophytoplankton in lakes. However, accurate determination of cell size and biomass remain challenges for microscopy and especially for flow cytometry.
  • 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.
  • Aalto, Sanni (Helsingfors universitet, 2017)
    Microalgae are promising raw materials for food- and biotechnology because they contain a lot of proteins, unsaturated fatty acids, pigments, vitamins and minerals. There are few studies on vitamin B in microalgae and some of them are based on partly inaccurate methods. Microalgae in general, analytical methods regarding their analysis and how they use vitamins were discussed in the literature part of this thesis. The structures, chemical properties and occurrence in foods as well as commonly used analytical methods of the vitamins in question were presented. The aim of the experimental part of this thesis was to analyse commercially marketed microalgae supplements (Chlorella sp. and Arthrospira sp. (spirulina)) and laboratory-grown microalga (Euglena gracilis) as potential sources of folate, niacin, vitamin B2 and B12. Contents of vitamin B12, B2 and niacin were analysed using UHPLC method separately validated for each vitamin. The total folate content was analysed microbiologically and folate vitamers by using UHPLC. The vitamin B12 was analysed microbiologically and the active forms of vitamin B12 were confirmed using LC-MS. Acid hydrolysis was used in analysing niacin content. The total folate content in chlorella supplements was of the same order when analysed microbiologically or with UHPLC. Instead, in spirulina supplements the microbiologically analysed total folate content was higher than the total folate content based on the sum of folate vitamers analysed with UHPLC. At most, the total folate content of E. gracilis -sample was 3-fold higher than in commercial microalgae supplements. Especially in spirulina supplements, the vitamin B12 contents were clearly higher when analysed microbiologically than they were when analysed with UHPLC. The difference was most likely due to pseudocobalamin that resembled vitamin B12. On average E. gracilis -samples had higher vitamin B2 content than the commercial supplements. E. gracilis -samples and chlorella supplements contained more niacin than spirulina supplements. According to this thesis, commercially marketed microalgae supplements contained different amounts of vitamin B. Chlorella sp. was proved to be a great source of folate, vitamin B12 and niacin and moderate source of B2. The majority of vitamin B12 in Arthrospira sp. (spirulina) was pseudocobalamin. Despite that, spirulina supplements proved to be a moderate source of vitamin B12. On average, E. gracilis had the highest vitamin B content and it would potentially be an excellent source of vitamin B – if it was accepted for food use.
  • Jerney, Jacqueline; Ahonen, Salla Annika; Hakanen, Päivi; Suikkanen, Sanna; Kremp, Anke (2019)
    Abstract In seasonal environments, strong gradients of environmental parameters can shape life cycles of phytoplankton. Depending on the rate of environmental fluctuation, specialist or generalist strategies may be favored, potentially affecting life cycle transitions. The present study examined life cycle transitions of the toxin producing Baltic dinoflagellate Alexandrium ostenfeldii and their regulation by environmental factors (temperature and nutrients). This investigation aimed to determine if genetic recombination of different strains is required for resting cyst formation and if newly formed cysts are dormant. Field data (temperature, salinity) and sediment surface samples were collected from a site with recurrent blooms and germination and encystment experiments were conducted under controlled laboratory conditions. Results indicate a lack of seasonal germination pattern, set by an endogenous rhythm, as commonly found with other dinoflagellates from the Baltic Sea. Germination of quiescent cysts was triggered by temperatures exceeding 10°C and combined nutrient limitation of nitrogen and phosphorus or a drop in temperature from 16 to 10°C triggered encystment most efficiently. Genetic recombination was not mandatory for the formation of resting cysts, but supported higher numbers of resistant cysts and enhanced germination capacity after a resting period. Findings from this study confirm that A. ostenfeldii follows a generalist germination and cyst formation strategy, driven by strong seasonality, which may support its persistence and possibly expansion in marginal environments in the future, if higher temperatures facilitate a longer growth season. This article is protected by copyright. All rights reserved.
  • Peltomaa, Elina; Johnson, Matthew D.; Taipale, Sami J. (2018)
    Microalgae have the ability to synthetize many compounds, some of which have been recognized as a source of functional ingredients for nutraceuticals with positive health effects. One well-known example is the long-chain polyunsaturated fatty acids (PUFAs), which are essential for human nutrition. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the two most important long-chain omega-3 (-3) PUFAs involved in human physiology, and both industries are almost exclusively based on microalgae. In addition, algae produce phytosterols that reduce serum cholesterol. Here we determined the growth rates, biomass yields, PUFA and sterol content, and daily gain of eight strains of marine cryptophytes. The maximal growth rates of the cryptophytes varied between 0.34-0.70 divisions day(-1), which is relatively good in relation to previously screened algal taxa. The studied cryptophytes were extremely rich in -3 PUFAs, especially in EPA and DHA (range 5.8-12.5 and 0.8-6.1 mu g mg dry weight(-1), respectively), but their sterol concentrations were low. Among the studied strains, Storeatula major was superior in PUFA production, and it also produces all PUFAs, i.e., -linolenic acid (ALA), stearidonic acid (SDA), EPA, and DHA, which is rare in phytoplankton in general. We conclude that marine cryptophytes are a good alternative for the ecologically sustainable and profitable production of health-promoting lipids.
  • van Leeuwe, Maria A.; Tedesco, Letizia; Arrigo, Kevin R.; Assmy, Philipp; Campbell, Karley; Meiners, Klaus M.; Rintala, Janne-Markus; Selz, Virginia; Thomas, David N.; Stefels, Jacqueline (2018)
    Sea ice is one the largest biomes on earth, yet it is poorly described by biogeochemical and climate models. In this paper, published and unpublished data on sympagic (ice-associated) algal biodiversity and productivity have been compiled from more than 300 sea-ice cores and organized into a systematic framework. Significant patterns in microalgal community structure emerged from this framework. Autotrophic flagellates characterize surface communities, interior communities consist of mixed microalgal populations and pennate diatoms dominate bottom communities. There is overlap between landfast and pack-ice communities, which supports the hypothesis that sympagic microalgae originate from the pelagic environment. Distribution in the Arctic is sometimes quite different compared to the Antarctic. This difference may be related to the time of sampling or lack of dedicated studies. Seasonality has a significant impact on species distribution, with a potentially greater role for flagellates and centric diatoms in early spring. The role of sea-ice algae in seeding pelagic blooms remains uncertain. Photosynthesis in sea ice is mainly controlled by environmental factors on a small scale and therefore cannot be linked to specific ice types. Overall, sea-ice communities show a high capacity for photoacclimation but low maximum productivity compared to pelagic phytoplankton. Low carbon assimilation rates probably result from adaptation to extreme conditions of reduced light and temperature in winter. We hypothesize that in the near future, bottom communities will develop earlier in the season and develop more biomass over a shorter period of time as light penetration increases due to the thinning of sea ice. The Arctic is already witnessing changes. The shift forward in time of the algal bloom can result in a mismatch in trophic relations, but the biogeochemical consequences are still hard to predict. With this paper we provide a number of parameters required to improve the reliability of sea-ice biogeochemical models.
  • Anttila, Pekka (Helsingin yliopisto, 2017)
    Microalgae are the most primitive and simple members of plant kingdom, unicellular or colonial and can be found worldwide. Microalgae are promising organism for producing sustainable biomass and microalgae can be used to produce proteins, lipids, colourants, vitamins and carbohydrates to food industry and can be used as feed for animals and source for biofuels. The objective of this study was to select the most effective extraction solvent and develop and optimize an accelerated solvent extraction (ASE) method for microalgal lipids. ASE is an extraction technique that needs only small amounts of solvents and uses elevated temperature and pressure for better extractability. Study had two separated parts; 1. Choosing the best solvent for ASE, 2. Optimizing extraction conditions. Study was made with two freeze dried biomasses; Euglena gracilis and Selenastrum Sp. Choosing an extraction solvent for ASE was made between acetone, ethanol and 2-ethoxyethanol and those were compared for Bligh and Dyer chloroform- methanol-water solvent extraction. Lipid yields were analyzed as total fat as sum of fatty acid methyl esters and fatty acid composition with GC-FID. Overview of lipidclasses was studied with TLC. Tocopherol analysis was made with NP-HPLC-FLD and carotenoids and chlophylls were analyzed with UV-VIS spectroscopy. Optimizing the extraction conditions was made with experimental design program with 2*15 samples in different extraction conditions with ethanol as solvent. Evaluation of results was made by total fat, omega-3 fattyacids EPA and DHA, tocopherol, carotenoid and chlorophyll contents. Optimized extraction conditions were: Temperature 125 ⁰C, Extraction time 11 min, 1 extraction cycle and Pressure 1500 psi. Temperature had the greatest effect on the studied extraction parameters.
  • Salmi, Pauliina; Eskelinen, Matti A.; Leppänen, Matti T.; Pölönen, Ilkka (MDPI AG, 2021)
    Plants 2021, 10(2), 341
    Spectral cameras are traditionally used in remote sensing of microalgae, but increasingly also in laboratory-scale applications, to study and monitor algae biomass in cultures. Practical and cost-efficient protocols for collecting and analyzing hyperspectral data are currently needed. The purpose of this study was to test a commercial, easy-to-use hyperspectral camera to monitor the growth of different algae strains in liquid samples. Indices calculated from wavebands from transmission imaging were compared against algae abundance and wet biomass obtained from an electronic cell counter, chlorophyll a concentration, and chlorophyll fluorescence. A ratio of selected wavebands containing near-infrared and red turned out to be a powerful index because it was simple to calculate and interpret, yet it yielded strong correlations to abundances strain-specifically (0.85 < r < 0.96, p < 0.001). When all the indices formulated as A/B, A/(A + B) or (A − B)/(A + B), where A and B were wavebands of the spectral camera, were scrutinized, good correlations were found amongst them for biomass of each strain (0.66 < r < 0.98, p < 0.001). Comparison of near-infrared/red index to chlorophyll a concentration demonstrated that small-celled strains had higher chlorophyll absorbance compared to strains with larger cells. The comparison of spectral imaging to chlorophyll fluorescence was done for one strain of green algae and yielded strong correlations (near-infrared/red, r = 0.97, p < 0.001). Consequently, we described a simple imaging setup and information extraction based on vegetation indices that could be used to monitor algae cultures.
  • Zhang, Yangyang (Helsingin yliopisto, 2017)
    The literature review introduced the chemistry of sterols and presented the sterols found in microalgae, and placed emphasis on the analytical methods used for studying sterols in microalgae. A brief discussion about application of microalgae-derived sterols was also included. The aim of this work was to learn about the sterol compositions in microalgae: Euglena gracilis and Selenastrum sp.. The common analytical methods of sterols are not suitable when applied to microalgae. Traditional alkaline hydrolysis may lead to an underestimation of total sterol content, because it cannot break acetal bond in steryl glycoside (SG). Additional acid hydrolysis for determining SG may lead to isomerization or decomposition of Δ7-sterols, which are the main sterols in green algae. A combination of alkaline hydrolysis and enzymatic hydrolysis was performed in this study. Firstly, sterol contents were determined using two methods: direct saponification and accelerated solvent extraction followed by saponification. Secondly, sterol classes: free sterol (FS), steryl ester (SE), and SG were determined by fractionation using solid phase extraction, followed by alkaline hydrolysis (FS and SE) and enzymatic hydrolysis (SG). Sterols were quantified using an internal standard and determined by GC-FID as their trimethylsilyl ether derivatives and identified by GC-MS. Euglena gracilis contained three major sterols: ergosterol and corbisterol, and Selenastrum sp. contained Δ7-ergosterol, chondrillasterol, and Δ7-chondrillasterol. Sterol contents ranged from 0.68-3.24 mg/g dry matter in Euglena gracilis, of which ergosterol constituted 68-93%. Sterol content in Selenastrum sp. was > 9 mg/g dry matter, with 36% Δ7-ergosterol, 12% chondrillasterol, and 52% Δ7-chondrillasterol. Comparison between the two extraction methods showed that ASE had a lower sterol yield than direct saponification. In E. gracilis, SE compromised 20-24%, FS 60-65%, and SG 11-12%. In Selenastrum, SE compromised only 1%, FS 74%, and SG 25%. The findings suggested that data on sterol composition ought to be viewed with caution. Underestimation of total sterol content may result from missing remarkable amounts of SG in certain microalgae species.
  • 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.
  • Lamminen, M.; Halmemies-Beauchet-Filleau, A.; Kokkonen, T.; Vanhatalo, A.; Jaakkola, S. (2019)
    Alternative protein sources such as microalgae and faba beans may have environmental benefits over rapeseed. We studied the effects of rapeseed meal (RSM) or faba beans (FB) as a sole protein feed or as protein feeds partially substituted with Spirulina platensis (spirulina) microalgae on milk production, N utilization, and AA metabolism of dairy cows. Eight multiparous Finnish Ayrshire cows (113 +/- 36.3 d in milk; mean +/- SD) were used in a balanced, replicated 4 x 4 Latin square with 2 x 2 factorial arrangement of treatments and 21-d periods. Four cows in one Latin square were rumen cannulated. Treatments were 2 isonitrogenously fed protein sources, RSM or rolled FB, or one of these sources with half of its crude protein substituted by spirulina (RSM-SPI and FB-SPI). Cows had ad libitum access to total mixed rations consisting of grass silage, barley, sugar beet pulp, minerals, and experimental protein feed. The substitution of RSM with FB did not affect dry matter intake (DMI) but decreased neutral detergent fiber intake and increased the digestibility of other nutrients. Spirulina in the diet decreased DMI and His intake. Spirulina had no effect on Met intake in cows on RSM diets but increased it in those on FB diets. Energy-corrected milk (ECM) and protein yields were decreased when RSM was substituted by FB. Milk and lactose yields were decreased in cows on the RSM-SPI diet compared with the RSM diet but increased in those on FB-SPI compared with FB. The opposite was true for milk fat and protein concentrations; thus, spirulina in the diet did not affect ECM. Feed conversion efficiency (ECM: DMI) increased in cows on FB diets with spirulina, whereas little effect was observed for those on RSM diets. The substitution of RSM by FB decreased arterial concentration of Met and essential AA. Spirulina in the diet increased milk urea N and ruminal NH4-N and decreased the efficiency of N utilization in cows on RSM diets, whereas those on FB diets showed opposite results. Met likely limited milk production in cows on the FB diet as evidenced by the decrease in arterial Met concentration and milk protein yield when RSM was substituted by FB. The results suggest the potential to improve milk production response to faba beans with supplementation of Met-rich feeds such as spirulina. This study also confirmed spirulina had poorer palatability than RSM and FB despite total mixed ration feeding and lower milk production when spirulina partially replaced RSM.
  • Spilling, Kristian; Seppälä, Jukka; Schwenk, Dagmar; Rischer, Heiko; Tamminen, Timo (Springer, 2021)
    Journal of Applied Phycology 33: 3
    There is a growing demand for marine omega-3 fatty acids (FAs) that is produced in high amounts by some microalgae. Here we determined the FA profiles of two cold water adapted diatoms, Chaetoceros wighamii and Thalassiosira baltica. The cultures were acclimated to different temperatures (3, 7, 11, 15, and 19 °C) and irradiance (20, 40, 130, and 450 μmol photons m−2 s−1) and the FA profiles were determined in exponential and stationary growth phases, the latter induced by different nutrient limitation (N, P, and Si). The maximum growth rate was obtained by both species at 11 °C, ≥ 130 μmol photons m−2 s−1 and was 0.8 day−1 and 0.6 day−1 for C. wighamii and T. baltica, respectively. Both species contained relatively high amounts of eicosapentaenoic acid (EPA). Thalassiosira baltica accumulated maximally ~ 30 mg EPA g−1 ash-free dry weight (AFDW) under Si-limitation. The content of docosahexaenoic acid (DHA) was lower, reaching up to 4 mg DHA g−1 AFDW in T. baltica. The concentration of EPA correlated positively with the chlorophyll a:carbon ratio, suggesting that it is bound to membranes in the photosynthetic apparatus and the EPA content in T. baltica was high enough to consider it as a potent candidate for cultivation under cold (< 15 °C) conditions. Covering a wide range of environmental conditions, the strongest differentiation in FA profiles was observed between the species with the growth phase/nutrient limitation pattern as the second most important driver of the FA composition.