Metabolic pathways for biosynthesis and degradation of starch in Tetraselmis chui during nitrogen deprivation and recovery

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.Metabolic pathways for biosynthesis and degradation of starch in Tetraselmis chui during nitrogen deprivation and recoverypublishedVersio

Starch-Rich Microalgae as an Active Ingredient in Beer Brewing

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.Starch-Rich Microalgae as an Active Ingredient in Beer BrewingpublishedVersio

Use of algae technology for production of biohydrogen from green microalgae: Possibilities for a practical sustainable process and diversity at both species selection, culturing and gene transcript levels

Algae technology represents an extensive research field which has developed rapidly over the last decades. The research activities extend from algae cultivation including CO2 capture, production of commercial products such as health food, aquaculture and animal feed, production of valuable metabolites, to conversion of solar energy into energy carriers like biohydrogen or biodiesel. A combination of several aspects of algae technology into a multidisciplinary process is proposed in this work. Valuable metabolites produced by algae include for example carotenoids, unsaturated fatty acids, vitamins, glycerol, components with medical activities and a number of antioxidants. Many of these are secondary metabolites produced as a response to different forms of environmental stress, and they may function as protection mechanisms to avoid damage to the cells. Biohydrogen from green microalgae is an expanding field which has made great progress through the last decade. By exposing some species of algae to environmental stress, e.g. by depriving the algae of sulfur in light, it is possible to produce significant amounts of hydrogen gas. However, this technology is still in its infancy, and there is significant potential for technology development and improvement at every level. In this study, the possibility of producing hydrogen from solar energy by using green microalgae is explored at species selection-, culturing- and gene transcription levels. It is demonstrated that there is a considerable number of species currently known to have potential for hydrogen production, and the same is true for production of valuable metabolites. The effects of different stress reactions on production of the valuable components are described, along with the purpose of their production. This knowledge can be used to evaluate the possibilities for producing hydrogen and high value products efficiently in the same process. Hydrogen production under sulfur deprivation is explored in several species of green algae under controlled conditions, and Chlamydomonas noctigama shows the ability to produce hydrogen with efficiency comparable to the model organism Chlamydomonas reinhardtii. The ability to produce hydrogen under sulfur deprivation is also explored in relation to the different species’ ability to show heterotrophic or mixotrophic growth on acetate. A photobioreactor specifically designed for algae hydrogen production is described for lab scale research purposes, including considerations for measurement devices and materials choice. Hydrogen production by the algae C. noctigama is further explored at molecular level. By using RT-PCR followed by PCR with degenerate primers, mRNA with homology towards green algal hydrogenases was identified. The cDNA sequences were translated to putative amino acid sequences, and analyzed in respect to amino acids characteristic for green algal hydrogenases and amino acids which share characteristics with both hydrogenases and narf-like proteins. These results were used to evaluate the identification of the mRNA sequences found in C. noctigama. While other green algae have been shown to contain two different hydrogenases, it is here demonstrated that C. noctigama is able to transcribe three distinct genes which share essential characteristics with hydrogenases. The combination of these results provides valuable insights at several levels of a combined process for production of biohydrogen and other valuable products. Further studies of these topics may result in a sustainable process where solar energy can be converted into hydrogen in an integrated manner, where production efficiencies are sufficient for an economic exploitation of algal technology using algal stress reactions

Mikroalgers potensial som proteinkilde i fôr til storfe og gris. Selvberging i den nye bioøkonomien

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..

Design and construction of a photobioreactor for hydrogen production, including status in the field

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.publishedVersio

First Apocarotenoids Profiling of Four Microalgae Strains

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.First Apocarotenoids Profiling of Four Microalgae StrainspublishedVersio

Bioactive peptides from microalgae: Focus on anti-cancer and immunomodulating activity

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

Bioactive peptides from microalgae: Focus on anti-cancer and immunomodulating activity

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

Growth strategies of Chlorella vulgaris in seawater for a high production of biomass and lipids suitable for biodiesel

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

Protein Enrichment of Wheat Bread with Microalgae: Microchloropsis gaditana, Tetraselmis chui and Chlorella vulgaris

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.publishedVersio