Kari Skjånes
Forsker
Lenker
ResearchGateBiografi
Kari har doktorgrad innen mikroalgeteknologi fra UiB, med hovedvekt på dyrkingsteknologi. Forskningen har fokus på mikroalger til bruk i mat og fôr, der dyrkingsmetoder og stressfysiologi blir brukt til å fremstille algebiomasse med komposisjon som er tilpasset bruk i spesifikke produkter. Mikroalger som kilde til protein, fettsyrer (PUFA) og pigmenter (f.eks. karotenoider), er viktige elementer. NIBIOs pilotanlegg for mikroalger på Vollebekk på Ås med storskala fotobioreaktorer blir brukt til å forske på oppskalering av dyrkingsmetoder som er utviklet i labskala, og til produksjon av algebiomasse for utvikling av ulike mikroalgeprodukter. Hun jobber i tillegg med psykrofile mikroalger og andre alger tilpasset lave temperaturer, som kilde til bioaktive stoffer gjennom bioprospektering.
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Ralf Rautenberger Alexandre Detain Kari Skjånes Peter Simon Claus Schulze Viswanath Kiron Daniela Morales SanchezSammendrag
Chlorella vulgaris is a freshwater microalga that synthesises large amounts of saturated lipids, which makes it suitable for production of bioenergy and biofuels. Since its cultivation usually requires freshwater, it competes with agriculture, economic development and ecological conservation for this limited natural resource. This study investigated the possibility of the partial replacement of freshwater by seawater (50 %) in the growth medium for a more sustainable biomass and lipid production. Chlorella vulgaris 211-11b was cultivated as shake-flask cultures in Bold's Basal Medium (BBM) formulated with 50 % freshwater and 50 % seawater under photoautotrophic, mixotrophic and heterotrophic conditions for eight days with glucose as organic carbon source in the latter two cases. The alga's best growth performance and highest lipid contents (49 % DW−1), dominated by palmitioleic and oleic acid, occurred under mixotrophic rather than photoautotrophic and heterotrophic conditions. This study demonstrates a more economic and ecologically sustainable biomass and lipid production of C. vulgaris by saving 50 % freshwater, which is available for other purposes.
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Giorgia Carnovale Carmen Lama Sonia Torres Filipa Rosa Lalia Mantecon Svein Jarle Horn Kari Skjånes Carlos InfanteSammendrag
Tetraselmis chui is known to accumulate starch when subjected to stress. This phenomenon is widely studied for the purpose of industrial production and process development. Yet, knowledge about the metabolic pathways involved is still immature. Hence, in this study, transcription of 27 starch-related genes was monitored under nitrogen deprivation and resupply in 25 L tubular photobioreactors. T. chui proved to be an efficient starch producer under nitrogen deprivation, accumulating starch up to 56% of relative biomass content. The prolonged absence of nitrogen led to an overall down-regulation of the tested genes, in most instances maintained even after nitrogen replenishment when starch was actively degraded. These gene expression patterns suggest post-transcriptional regulatory mechanisms play a key role in T. chui under nutrient stress. Finally, the high productivity combined with an efficient recovery after nitrogen restitution makes this species a suitable candidate for industrial production of high-starch biomass.
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Vibeke Lind Pål Trosvik Eric de Muincke Kari Skjånes Grete H. M. Jørgensen Stig A. BorgvangSammendrag
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Giorgia Carnovale Shaun Allan Leivers Filipa Rosa Hans Ragnar Norli Edvard Hortemo Trude Wicklund Svein Jarle Horn Kari SkjånesSammendrag
Microalgal biomass is widely studied for its possible application in food and human nutrition due to its multiple potential health benefits, and to address raising sustainability concerns. An interesting field whereby to further explore the application of microalgae is that of beer brewing, due to the capacity of some species to accumulate large amounts of starch under specific growth conditions. The marine species Tetraselmis chui is a well-known starch producer, and was selected in this study for the production of biomass to be explored as an active ingredient in beer brewing. Cultivation was performed under nitrogen deprivation in 250 L tubular photobioreactors, producing a biomass containing 50% starch. The properties of high-starch microalgal biomass in a traditional mashing process were then assessed to identify critical steps and challenges, test the efficiency of fermentable sugar release, and develop a protocol for small-scale brewing trials. Finally, T. chui was successfully integrated at a small scale into the brewing process as an active ingredient, producing microalgae-enriched beer containing up to 20% algal biomass. The addition of microalgae had a noticeable effect on the beer properties, resulting in a product with distinct sensory properties. Regulation of pH proved to be a key parameter in the process.
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Giorgia Carnovale Svein Jarle Horn Carlos Infante Volha Shapaval Edvard Hortemo Kari SkjånesSammendrag
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Giorgia Carnovale Svein Jarle Horn Carlos Infante Volha Shapaval Edvard Hortemo Kari SkjånesSammendrag
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In addition to the rapidly expanding field of using microalgae for food and feed, microalgae represent a tremendous potential for new bioactive compounds with health-promoting effects. One field where new therapeutics is needed is cancer therapy. As cancer therapy often cause severe side effects and loose effect due to development of drug resistance, new therapeutic agents are needed. Treating cancer by modulating the immune response using peptides has led to unprecedented responses in patients. In this review, we want to elucidate the potential for microalgae as a source of new peptides for possible use in cancer management. Among the limited studies on anti-cancer effects of peptides, positive results were found in a total of six different forms of cancer. The majority of studies have been performed with different strains of Chlorella, but effects have also been found using peptides from other species. This is also the case for peptides with immunomodulating effects and peptides with other health-promoting effects (e.g., role in cardiovascular diseases). However, the active peptide sequence has been determined in only half of the studies. In many cases, the microalga strain and the cultivation conditions used for producing the algae have not been reported. The low number of species that have been explored, as opposed to the large number of species available, is a clear indication that the potential for new discoveries is large. Additionally, the availability and cost-effectiveness of microalgae make them attractive in the search for bioactive peptides to prevent cancer.
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Stig A. Borgvang Dorinde Mechtilde Meike Kleinegris Viswanath Kiron Katerina Kousoulaki Maria Barbosa Anabela Raymundo Carlos Unamunzaga Anne Kjersti Uhlen Sander Hazewinkel Hans Torstein Kleivdal Trude Wicklund Kai Kristoffer Lie Nils-Arne Ekerhovd Kristian Fuglseth Dag Hjelle Arne Edvard Rosland Hortemo Hans Petter Kleppen Jørund Hagen Helen Haaland Per Fredriksen Shuichi Satoh Rene Wijffels Kari SkjånesSammendrag
The knowledge- and technology platform developed within the ALGAE TO FUTURE project aims to lay a foundation for an industrial microalgae production in Norway. In the project ALGAE TO FUTURE, funded by the Norwegian Research Council 2017-2021, with a consortium of 20 national and international research and industry partners, research and product development of microalgae biomass have been approached from multiple angles merging multiple research fields. The focus of the research has been bioprocess developments linked to lipids, carbohydrates and proteins, where species selection and cultivation conditions are used to obtain microalgae biomass with specific nutrient composition targeting specific products. We have chosen to target the development of three example products, namely 1) bread using algae biomass with high protein content, 2) beer using algae biomass with high content of starch and starch-degrading enzymes, and 3) fish feed using algae biomass with high PUFA content. These case studies have been chosen in order to demonstrate the use of algal biomass from various algae species with highly different nutrient composition suitable for different products. We have in this project studied the whole process line from small scale microalgae cultivation technology, upscaling cultivation, processing of algae biomass, shelf life, food/ feed product development, food safety and consumers attitudes. Some highlights from the four-year project period will be presented. Results from these activities may contribute towards the use of microalgae as part of the future Norwegian bioeconomy.
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Waqas Muhammad Qazi Simon Ballance Katerina Kousoulaki Anne Kjersti Uhlen Dorinde Mechtilde Meike Kleinegris Kari Skjånes Anne RiederSammendrag
Cell wall disrupted and dried Microchloropsis gaditana (Mg), Tetraselmis chui (Tc) and Chlorella vulgaris (Cv) microalgae biomasses, with or without ethanol pre‐treatment, were added to wheat bread at a wheat flour substitution level of 12%, to enrich bread protein by 30%. Baking performance, protein quality and basic sensory properties were assessed. Compared to wheat, Mg, Tc and Cv contain higher amounts of essential amino acids and their incorporation markedly improved protein quality in the bread (DIAAS 57–66 vs 46%). The incorporation of microalgae reduced dough strength and bread volume and increased crumb firmness. This was most pronounced for Cv and Tc but could be improved by ethanol treatment. Mg gave adequate dough strength, bread volume and crumb structure without ethanol treatment. To obtain bread of acceptable smell, appearance, and colour, ethanol treatment was necessary also for Mg as it markedly reduced the unpleasant smell and intense colour of all algae breads. Ethanol treatment reduced the relative content of lysine, but no other essential amino acids. However, it also had a negative impact on in vitro protein digestibility. Our results show that Mg had the largest potential for protein fortification of bread, but further work is needed to optimize pre‐processing and assess consumer acceptance.
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Giorgia Carnovale Filipa Rosa Volha Shapaval Simona Dzurendova Achim Kohler Trude Wicklund Svein Jarle Horn Maria J. Barbosa Kari SkjånesSammendrag
The use of microalgal starch has been studied in biorefinery frameworks to produce bioethanol or bioplastics, however, these products are currently not economically viable. Using starch-rich biomass as an ingredient in food applications is a novel way to create more value while expanding the product portfolio of the microalgal industry. Optimization of starch production in the food-approved species Chlorella vulgaris was the main objective of this study. High-throughput screening of biomass composition in response to multiple stressors was performed with FTIR spectroscopy. Nitrogen starvation was identified as an important factor for starch accumulation. Moreover, further studies were performed to assess the role of light distribution, investigating the role of photon supply rates in flat panel photobioreactors. Starch-rich biomass with up to 30% starch was achieved in cultures with low inoculation density (0.1 g L−1) and high irradiation (1800 µmol m−2 s−1). A final large-scale experiment was performed in 25 L tubular reactors, achieving a maximum of 44% starch in the biomass after 12 h in nitrogen starved conditions.
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Giorgia Carnovale Filipa Rosa Volha Shapaval Simona Dzurendova Achim Kohler Trude Wicklund Svein Jarle Horn Maria Barbosa Kari SkjånesSammendrag
ABSTRACT The use of microalgal starch has been studied in biorefinery frameworks to produce bioethanol or bioplastics, however, these products are currently not economically viable. Using starch−rich biomass as an ingredient in food applications is a novel way to create more value while expanding the product portfolio of the microalgal industry. Optimization of starch production in the food−approved species Chlorella vulgaris was the main objective of this study. High−throughput screening of biomass composition in response to multiple stressors was performed with FTIR spectroscopy and nitrogen starvation was identified as an important factor for starch accumulation. Further studies were subsequently performed to assess the role of light distribution, investigating photon supply rates in flat panel photobioreactors. Biomass specific photon supply rate proved to have a strong effect on the accumulation of storage compounds and starch−rich biomass with up to 30% starch was achieved in cultures with low inoculation density (0.1 g L−1) and high irradiation (1800 μmol m−2 s−1). A final large scale experiment was performed in 25 L tubular reactors, achieving a maximum of 44% starch in the biomass after 12 hours in nitrogen starved conditions. Keywords: Chlorella vulgaris, starch, FTIR, photon supply rate, microalgae
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Kari Skjånes Hanne Skomedal Giorgia Carnovale Volha Shapaval Achim Kohler Stig A. BorgvangSammendrag
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Mariosimone Zoccali Daniele Giuffrida Fabio Salafia Carmen Socaciu Kari Skjånes Paola Dugo Luigi MondelloSammendrag
Both enzymatic or oxidative carotenoids cleavages can often occur in nature and produce a wide range of bioactive apocarotenoids. Considering that no detailed information is available in the literature regarding the occurrence of apocarotenoids in microalgae species, the aim of this study was to study the extraction and characterization of apocarotenoids in four different microalgae strains: Chlamydomonas sp. CCMP 2294, Tetraselmis chuii SAG 8-6, Nannochloropsis gaditana CCMP 526, and Chlorella sorokiniana NIVA-CHL 176. This was done for the first time using an online method coupling supercritical fluid extraction and supercritical fluid chromatography tandem mass spectrometry. A total of 29 different apocarotenoids, including various apocarotenoid fatty acid esters, were detected: apo-12’-zeaxanthinal, β-apo-12’-carotenal, apo-12-luteinal, and apo-12’-violaxanthal. These were detected in all the investigated strains together with the two apocarotenoid esters, apo-10’-zeaxanthinal-C4:0 and apo-8’-zeaxanthinal-C8:0. The overall extraction and detection time for the apocarotenoids was less than 10 min, including apocarotenoids esters, with an overall analysis time of less than 20 min. Moreover, preliminary quantitative data showed that the β-apo-8’-carotenal content was around 0.8% and 2.4% of the parent carotenoid, in the C. sorokiniana and T. chuii strains, respectively. This methodology could be applied as a selective and efficient method for the apocarotenoids detection.
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Kari Skjånes Maria Barbosa Rene Wijffels Dorinde Kleinegris Katerina Kousoulaki Anne Kjersti Uhlen Viswanath Kiron Kai Kristoffer Lie Nils-Arne Ekerhovd Kristian Fuglseth Carlos Unamunzaga Stig A. BorgvangSammendrag
With regard to the rapidly growing world population, microalgae can be regarded as one of the most promising resources for the sustainable supply of commodities for food and feed applications. Although the use of commercial microalgae for food has been mainly limited to dietary supplements, the recent development of more cost-effective production technology makes it feasible to explore various other food applications. In the project ALGAE TO FUTURE, funded by the Norwegian Research Council, we have developed a consortium of 20 research and industry partners to approach this topic from multiple angles merging multiple research fields. The Vision is to contribute towards a viable Norwegian microalgae industry within 10 years. The focus of the research is on bioprocess developments linked to lipids, carbohydrates and proteins, where cultivation conditions are used to obtain microalgae biomass with specific nutrient composition targeting specific products, without use of GMO. We have chosen to target the development of 3 example products, namely bread, beer and aquaculture feed, that will be produced in a commercial context towards the end of the project. These case studies have been chosen in order to demonstrate the use of algal biomass from various algae species with highly different nutrient composition suitable for different products. The project combines expertise on algae cultivation and optimisation at lab and pilot scales, fish feeding technology, biorefining, bioeconomy, baking technology, broadcast journalism and animation, food quality and safety with the experience of innovative farmer entrepreneurs, professional bakers, brewers and fish-feed producers in a cross-disciplinary manner.
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Gitte Søndergaard Dorinde Kleinegris Katerina Kousoulaki Nils-Arne Ekerhovd Stig A. Borgvang Kari Skjånes Anne Kjersti UhlenSammendrag
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Kari SkjånesSammendrag
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Poster – Microalgae: Active ingredients in brewing
Giorgia Carnovale, Kari Skjånes, Stig A. Borgvang
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Maria Hayes Leen Bastiaens Luisa Gouveia Spyros Gkelis Hanne Skomedal Kari Skjånes Patrick Murray Marco García-Vaquero Muge Isleten Hosoglu John Dodd Despoina Konstantinou Ivo Safarik Graziella Chini Zittelli Vytas Rimkus Victόria del Pino Koenraad Muylaert Christine Edwards Morten Laake Joana Gabriela Laranjeira da Silva Hugo Pereira Joana AbelhoSammendrag
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Stig A. Borgvang Katerina Kousoulaki Anne Kjersti Uhlen Kari Skjånes Sigbjørn Gjelsvik Nils-Arne Ekerhovd Vegard StorslettenSammendrag
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M. Hayes Hanne Skomedal Kari Skjånes H. Mazur-Marzec A. Torunska-Sitarz M. Catala M. Isleten Hosoglu M. García-VaqueroSammendrag
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Several species of microalgae and phototrophic bacteria are able to produce hydrogen under certain conditions. A range of different photobioreactor systems have been used by different research groups for lab-scale hydrogen production experiments, and some few attempts have been made to upscale the hydrogen production process. Even though a photobioreactor system for hydrogen production does require special construction properties (e.g., hydrogen tight, mixing by other means than bubbling with air), only very few attempts have been made to design photobioreactors specifically for the purpose of hydrogen production. We have constructed a flat panel photobioreactor system that can be used in two modes: either for the cultivation of phototrophic microorganisms (upright and bubbling) or for the production of hydrogen or other anaerobic products (mixing by “rocking motion”). Special emphasis has been taken to avoid any hydrogen leakages, both by means of constructional and material choices. The flat plate photobioreactor system is controlled by a custom-built control system that can log and control temperature, pH, and optical density and additionally log the amount of produced gas and dissolved oxygen concentration. This paper summarizes the status in the field of photobioreactors for hydrogen production and describes in detail the design and construction of a purpose-built flat panel photobioreactor system, optimized for hydrogen production in terms of structural functionality, durability, performance, and selection of materials. The motivations for the choices made during the design process and advantages/disadvantages of previous designs are discussed.
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Kari SkjånesSammendrag
Behovet for vegetabilsk protein til dyrefôr i norsk landbruk, blir per i dag ikke dekket av norskprodusert protein, og norsk kjøtt og melkeproduksjon er i dag avhengig av import. Totalt er 44% av ingrediensene til norsk kraftfôr importert, og import utgjør 93% av proteininnholdet. Mikroalger har høyere proteininnhold enn både tradisjonelle og alternative vegetabilske proteinkilder, og har i tillegg høyt innhold av andre næringsstoff som vitaminer, mineraler, flerumettede fettsyrer og antioksidanter. Næringsinnhold vil variere mye mellom artene, og i mange tilfeller kan næringssammensetningen styres med bruk av dyrkingsbetingelser. Forsøk med mikroalger som fôrkilde til storfe, gris og andre husdyr, har gitt gode resultater mht fôraksept, fôropptak, fordøyelighet, veksthastighet, totalvekt, fertilitet, melkeproduksjon, og proteininnhold i melk. Mikroalger blir i dag produsert kommersielt mange ulike steder i verden, og det meste blir solgt som dyrefôr eller helsekost. Det har vært mye forskning innen reaktorteknologi for produksjon av mikroalger de siste tiårene, og mange varianter av fotobioreaktorer har vært utprøvd. Algedyrking på norske gårdsbruk krever at dyrkingsteknologien blir tilpasset ressursgrunnlaget som foreligger, for optimal produksjon og bærekraft mht økonomi, miljø og ressursbruk. Informasjon som...
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Kari SkjånesSammendrag
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Marit Almvik Jihong Liu Clarke Lise Haug Susanne Friis Pedersen Maria Herrero Åsbjørn Karlsen Ingvar Kvane Anne-Kristin Løes Geo Van Leeuwen Margarita Novoa-Garrido Celine Rebours Siv Skar Kari Skjånes Øystein Svalheim Christian Uhlig Eivind VangdalSammendrag
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Kari Skjånes Stig A. Borgvang Thorsten Heidorn Celine Rebours Christian Guido Bruckner Margarita Novoa Garrido Åsbjørn KarlsenSammendrag
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Kari SkjånesSammendrag
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Kari SkjånesSammendrag
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Kari SkjånesSammendrag
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The production of hydrogen in green algae is catalyzed by FeFe- hydrogenases, which have high conversion efficiency and high oxygen sensitivity. Most green algae analyzed to date where hydrogenase genes are detected, have been shown to contain two distinct hydrogenases. However, very little is known about which functions the two different enzymes represent. There are also many unknowns within the mechanisms behind hydrogen production as to the roles hydrogenases play under different conditions, and consequently also about the potential for optimization of a hydrogen production process which could be found in this respect. The presented study focuses on the possibility for presence of more than two hydrogenases in a single green alga. A large number of degenerate primers were designed and used to produce 3"-RACE products, which in turn were used to design gene specific primers used for PCR and 5"-RACE reactions. The sequences were aligned with known algal hydrogenases to identify products which had homology to these. Products where homology was identified were then explored further. A high number of clones from each band were sequenced to identify products with similar lengths which would not show up as separate bands on a gel. Sequences found to have homology with algal hydrogenases were translated into putative amino acid sequences and analyzed further to obtain detailed information about the presence of specific amino acids with known functions in the enzyme. This information was used to evaluate the likelihood of these transcripts coding for true hydrogenases, versus hydrogenase-like or narf-like proteins. Conclusion: Evidence showing that Chlamydomonas noctigama is able to transcribe three genes which share a significant number of characteristics with other known algal FeFe-hydrogenases is presented . The three genes have been annotated hydA1, hydA2 and hydA3.
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Green algae are known to produce H2 under sulphur deprivation in a process called biophotolysis, where solar energy is used to split water and generate O2 and H2. There is still considerable potential for improvement and very little is known about how this mechanism varies between species. This is part of Bioforsk research activities linked to green algae and H2 production. In order to make a H2 production process from algae economically viable, we face several challenges, including bioreactor design, optimisation of environmental conditions, efficiency improvement by genetic and metabolic engineering. One possibility for improving the economical potential of a hydrogen production process also includes exploitation of the algal biomass which, as a result of stress reactions, may produce metabolites with pharmaceutical value. Joining forces with The Norwegian University of Life Science (UMB) and The Norwegian Forest and Landscape Institute, Bioforsk has established The Norwegian Centre for Bioenergy Research. Bioforsk has also taken a leading role on biogas in the newly established CenBio - a national Centre for Environmental- friendly Energy Research. The modern biogas laboratories are located close to facilities for plant growth studies, making them easy accessible for experimental studies of the entire chain from biomass to fertiliser. Research activities include innovative pre-treatment of substrates for increased biogas yield, effects of substrate mixtures for biogas production and digestate quality, biogas potential and biogas process studies, digestates as fertiliser, and effects on the environment and climate
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Kari SkjånesSammendrag
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Kari SkjånesSammendrag
Green microalgae can be used for a number of commercial applications, including health food for human consumption, aquaculture and animal feed, coloring agents, cosmetics and pharmaceuticals. Several products from green algae that are in use today, consist of metabolites which can be extracted from the algal biomass. The most well known examples are the carotenoids astaxanthin and Β-carotene, which are used as coloring agents and for health promoting purposes. Many species of green algae are able to produce valuable components for different uses, examples are antioxidants, several different carotenoids, polyunsaturated fatty acids, vitamins, anticancer and antiviral drugs. In many cases these components are secondary metabolites which are produced when the algae are exposed for stress conditions like for example nutrient deprivation, light intensity, temperature, salinity, pH and other. In other cases the components have been detected in algae grown under optimal conditions, and little is known about how an optimal production of each product could be induced and how their production would react to stress conditions. Some green algae have shown the ability to produce significant amounts of hydrogen gas during sulfur deprivation, a process which is currently extensively studied. At the moment, the majority of research in this field has focused on the model organism Chlamydomonas reinhardtii, but other species of green algae have also showed this ability. Currently there is scarce information available regarding the possibility for producing hydrogen and other valuable components in the same process. This study explores stress conditions which are known to induce production of the different valuable products in comparison with stress reactions leading to hydrogen production. Wild type species of green microalgae with ability to produce hydrogen during anaerobic conditions, and during sulfur deprivation are compared to species with known ability to produce high amounts of certain valuable metabolites. . This information is explored in order to form a basis for selection of wild type species for a future multidiciplinary process, where hydrogen production from solar energy is combined with production of valuable metabolites and other commercial uses of the algal biomass.
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Chitralekha Nag Dasgupta J. Jose Gilbert Peter Lindblad Thorsten Heidorn Stig A. Borgvang Kari Skjånes Debabrata DasSammendrag
Hydrogen production through biological routes is promising because they are environmentally friendly. Hydrogen production through biophotolysis or photofermentation is usually a two stage process. In the first stage CO2 is utilized for biomass production which is followed by hydrogen production in the second stage in anaerobic/sulfur deprived conditions in the next stage. The major challenges confronting the large scale production of biomass/hydrogen are limited not only on the performance of the photo bioreactors in which light penetration in dense cultures is a major bottleneck but also on the microbiology, biochemistry and molecular biology of the organisms. Other dependable factors include area/ volume (A/V) ratio, mode of agitation, temperature and gas exchange. Photobioreactors of different geometries are reported for biohydrogen production-Tubular, Flat plate, Fermentor type etc. Every reactor has its own advantages and disadvantages. No reactor is ideal for this purpose. Airlift, helical tubular and flat plate reactors are found most suitable with respect to biomass production. These bioreactors may be employed for hydrogen production with necessary modifications to overcome the existing bottlenecks like gas hold up, oxygen toxicity and improved agitation system. This review article attempts to focus on existing photobioreactors with respect to biomass generation and hydrogen production and the steps taken to improve its performance through engineering innovation that definitely help in the future construction of photobioreactors.
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Twenty-one species of green algae isolated from marine, freshwater and terrestrial environments were screened for the ability to produce H2 under anaerobic conditions. Seven strains found positive for H2 production under anaerobic conditions were also screened for the ability to produce H2 under sulfur (S) deprivation. In addition to the traditional model species Chlamydomonas reinhardtii, C. noctigama (freshwater) and C. euryale (brackish water) were able to produce significant amounts of H2 under S-deprivation. These species were also able to utilize acetate as a substrate for growth in light. The S-deprivation experiments were performed under photoheterotrophic conditions in a purpose-specific designed bioreactor, and it was shown that an automated pH adjustment feature was essential to maintain a stable pH in the cultures. Several materials commonly used in bioreactors, such as rubber materials, plastics and steel alloys, had a negative effect on the survival of S-deprived algae cultures. Unexpectedly, traces of H2 were produced under S-deprivation during O2 saturation in the cultures, possibly derived from local anaerobic environments formed in algal biofilms on the membranes covering the O2 electrodes.
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Many areas of algae technology have developed over the last decades, and there is an established market for products derived from algae, dominated by health food and aquaculture. In addition, the interest for active biomolecules from algae is increasing rapidly. The need for CO2 management, in particular capture and storage is currently an important technological, economical and global political issue and will continue to be so until alternative energy sources and energy carriers diminish the need for fossil fuels. This review summarizes in an integrated manner different technologies for use of algae, demonstrating the possibility of combining different areas of algae technology to capture CO2 and using the obtained algal biomass for various industrial applications thus bringing added value to the capturing and storage processes. Furthermore, we emphasize the use of algae in a novel biological process which produces H2 directly from solar energy in contrast to the conventional CO2 neutral biological methods. This biological process is a part of the proposed integrated CO2 management scheme.
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Many different species of microorganisms have one or more hydrogenase enzymes that reduce protons to molecular hydrogen under certain conditions. Upon sulfur deprivation, green algae can produce relatively large amounts of hydrogen in a sustainable process. The majority of research in this field has focused on Chlamydomonas reinhardtii, but other species of green algae are also able to produce hydrogen under sulfur deprivation. Using PCR reactions, we examined the presence of hydrogenase genes in marine and fresh water species of green algae that were able to produce hydrogen under sulfur deprived conditions. Primers were designed from conserved regions of the sequence of the two hydrogenase genes in C. reinhardtii, and used to screen for the presence of similar gene sequences in other species. PCR products that were sequenced suggest that genes for hydrogenase are present in C. noctigama and other species. Similarities and differences in the sequences of hydrogenase genes between C. reinhardtii and other species, will be presented.
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Sammendrag
The sun is an abundant energy source, and increasing efforts are made to find more efficient ways to exploit it, than commonly used today. Hydrogen is considered to be the energy carrier of the future, and the potential for a sustainable system where hydrogen is obtained directly from solar energy, has been studied extensively. One alternative is the process of biophotolysis. Sulfur starvation of the green algae Chlamydomonas reinhardtii is known to cause hydrogen production under illumination, by biophotolysis where solar energy is used to produce significant amounts of hydrogen involving parts of the photosynthetic process. So far, little is known about this process in other species, and in this work we have investigated different species of green algae with respect to hydrogen production under sulfur starvation. A number of algae cultures were screened with respect to physiological response to sulfur deprivation in small-scale laboratory cultures under controlled conditions. Test parameters included hydrogen production, reduction of oxygen production, changes in morphology and other aspects of physiology. Investigations of oxygen sensitivity of hydrogenases were also performed. It was shown that other species than C. reinhardtii are able to produce hydrogen under sulfur deprivation.
Sammendrag
Most energy carriers that are in common use today originate from solar energy. Hydrogen is considered to be the energy carrier of the future, and the potential for a sustainable system where hydrogen is obtained directly from solar energy, has been studied by several researchers over the years. Several groups of microorganisms have shown the ability to produce hydrogen by natural biological processes using solar energy. Efforts have been made to understand the mechanisms involved in photobiological hydrogen production from these organisms, and to optimise the process. This work has recently resulted in a significant breakthrough. It has been discovered that some species of green algae have the ability to produce significant amounts of hydrogen during sulphur starvation, which allows hydrogen to be produced in light. However, very little is known about how this process varies between species. We have chosen to investigate green algae, with the intention to examine a variety of species for hydrogen production during sulphur starvation. A number of algae cultures were screened with respect to physiological response to sulphur deprivation in small-scale laboratory cultures under controlled conditions. Results from both marine and fresh water algae will be presented.
