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Den stigende befolkningstilvækst øger efterspørgslen efter energi og ressourcer. Oliereserverne mindskes dog, og drivhusgasemissionerne fra forbrændingen af fossile brændstoffer påvirker det globale klima og forårsager global opvarmning. Behovet for alternative ressourcer og processer er derfor stigende.Makro- og mikroalger har evnen til at omdanne næringsstoffer til værdifuld biomasse, som er en god kilde til vitaminer, mineraler, lipider, proteiner og pigmenter. Biomassen repræsenterer derfor en lovende ressource for forskellige produkter, men er dog meget lidt udforsket som råmateriale til bioraffinaderier. Bioraffinaderier er et vigtigt redskab i udviklingen af en bæredygtig økonomi og inden for rammerne af bioraffinaderikonceptet kan flere bioprodukter så som mad, foder og biobrændstof produceres fra biomasse. Den specifikke sammensætning af det biologiske råmateriale afgør det potentielle produkt.I denne afhandling er mikro- og makroalger undersøgt som råmateriale til bioraffinaderi. Hovedformålet med dette arbejde er at udvikle forskellige bioraffinaderiordninger til produktion af proteinrige produkter, der skal anvendes som fødevarer og foderkosttilskud. Makroalgen anvendt i dette arbejde er Fingertang og Saccharina latissima, mens mikroalgeen er Chlorella sorokiniana, Chlorella vulgaris og Chlorella protothecoides.Derudover er effekten af høstsæsonen og placeringen på sammensætningen af højværdiprodukter, så som fenoler, og på biogaspotentialet for L. digitata og S. latissima blevet evalueret. Begge disse faktorer har en betydelig indvirkning på produktionen af de samlede fenoler og biogas. Særligt prøver høstet i sommeren, på grund af det høje indhold af sukker, repræsenterer det mest lovende råmateriale i udviklingen af en bioraffinaderi-proces.Forskellige industrielle metoder til at producere aminosyrer præsenteres herefter. Endvidere analyseres innovative teknikker til at øge proteinindholdet i den endelige biomasse, såsom mikroalger eller mikroroganismer, der skal anvendes som enkelte celleproteiner (SCP). Kombinationen af fototropisk vækst af C. sorokiniana med M. capsulatus fører til en innovativ løsning, hvor der kan opnås to produkter rige på proteiner.En anden strategi er udviklet i denne afhandling, baseret på en kombination af mikro- og makroalger. Faktisk blev mikroalgerne C. protothecoides dyrket heterotrofisk i makroalgen L. digitata hydrolyseret. Den endelige sammensætning af mikroalgalbiomassen viste, at proteinindholdet blev forøget fra 0,07 ± 0,01 g Protein gDM-1 til 0,44 ± 0,04 g Protein DM-1. Derfor viser de opnåede resultater, at denne løsning kan udgøre en interessant strategi, der skal anvendes i en bioraffineringsmetode.Endelig er en mikroalge-bioraffinaderistrategi blevet udviklet. Lutein repræsenterer et meget vigtigt pigment som er til stede i det makulære område af det menneskelige øje. Det er afgørende for beskyttelse mod lysinducerede retinale skader og ansvarlig for at opretholde menneskers knoglesundhed og forebygge visse sygdomme. Lutein og proteiner produceres med innovative metoder specifikt designet til mikroalgearter. Biogas bliver desuden produceret fra resterne af denne ekstraktionsprocesser.Resultaterne af denne undersøgelse viser at makro- og mikroalger er lovende biomasse i udviklingen af de fremtidige bioraffinaderier. The fast population growth is increasing the demand for energy and resources. However, the reserves of oil are diminishing and greenhouse emissions associated to its combustion are affecting the global climate causing global warming. Therefore the need for alternative resources and processes is becoming impellent. Macro- and microalgae have the ability to transform nutrients into valuable biomass. Being a good source of vitamins, minerals, lipids, proteins and pigments, they represent a promising source of various products. However these biomasses are still very little explored as biorefinery feedstocks. Biorefinery represents an important tool towards the development of a sustainable economy. Within the biorefinery framework several bioproducts, such as food, feed and biofuels, can be produced from biomass. The specific composition of the biomass feedstock determines the potential final product that can be obtained. In this thesis, micro- and macroalage were investigated as biorefinery feedstocks. The main aim of this work was developing different biorefinery strategies for the production of high value products, such as proteins or pigments, to be employed in the pharmaceutical or nutraceutical industry. The macroalgae used in this work were Laminaria digitata and Saccharina latissima, while the microalgae were Chlorella sorokiniana, Chlorella vulgaris and Chlorella protothecoides. Moreover, an evaluation of the effect of the harvesting season and location on the composition of high value products such as total phenolics and on the biogas potential for L. digitata and S. latissima was done. Both these factors had a significant impact on the accumulation of total phenolics in the algal biomass and on the biogas production. In particular, samples harvested in summer, because of the high content of sugars, showed to be the most promising feedstock in the development of biorefinery processes, containing 0.5 mgTPC gDM-1 and having a biomethane potential of 343.7 NmLCH4 g VS-1.Moreover, proteins being an interesting valuable product to be used as food and feed supplement, diverse industrial methods to produce amino acids and proteins were analyzed. Innovative techniques to increase the protein content in the final biomass, such as microalgae or microorganisms to be used as single cell proteins (SCP), were also investigated. The combination of phototropic growth of C. sorokiniana with Methylococcus capsulatus led to an innovative solution where two products rich in proteins (up to 43 %DM) were obtained. Another strategy developed in this thesis work was based on the combination of micro- and macroalgae to enhance protein production. Indeed, the microalgae C. protothecoides was grown heterotrophically in the macroalgae L. digitata hydrolyzed. The final composition of the microalgal biomass showed that the protein content was increased from 0.07 ± 0.01 gProtein gDM-1 to 0.44 ± 0.04 gProtein DM-1. The results obtained show that this solution may represent an interesting strategy to be applied in a biorefinery approach. Finally, a microalgae biorefinery strategy was developed. Lutein represents a very important pigment present in the macular region of the human eye. It is crucial in the protection against light-induced retinal damages and responsible for maintaining human bone health and preventing some diseases. Lutein and proteins were extracted by developing innovative methods specifically designed for microalgae species. From the initial algal biomass were extracted 0.8 ± 0.1 mg Lutein gDM-1 with a purity of 92.5 ± 1.2% and a calculated yield of 95%. Moreover, the final protein content in the fraction was 82.7 ± 3.1% w w-1with a protein yield of 55%. Finally, from the residues of this extraction processes, 372.7 ± 19.0 NmLCH4 gVS-1 of biogas were produced. The results obtained in this thesis work show that macro- and microalgae are promising biomasses for the development of the future biorefineries. |
