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Foredrag – Strain selection of Saccharina latissima for aquaculture in a freshwater-influenced fjord system in North Norway
Aquaculture of marine macroalgae is an important part of the world’s food production. In Norway, the fast-growing kelp Saccharina latissima has the highest potential for industrial biomass production. Aquaculture in the country’s fjords is economically more viable for SMEs, supports the development of IMTA and could allow the industry to approach the projected 20 million tons by 2050. However, S. latissima is exposed to a considerable decline in seawater salinity during the growth season, which affects the biomass production. This presentation shows results of industrial R&D projects in which the presence of “low-salinity tolerant” strains of S. latissima in a North Norwegian fjord and their responses to the seasonal salinity decline was studied. In a laboratory-based common garden experiment, sporophytes of S. latissima from different locations in Skjerstadfjorden were cultivated under different salinities for six weeks. Growth and photosynthetic parameters were measured to understand their physiological responses to salinity stress. Then their F1 generation were seeded on ropes and deployed at a commercial aquaculture site in Skjerstadfjorden to study strain-specific differences in biomass production and yield, optimal growth depths and biochemical composition of S. latissima. In addition, the aquaculture site was characterised by measurements of physical and chemical parameters. The projects’ results will help North Norwegian macroalgae producers to improve the biomass production and biochemical composition of S. latissima. These findings could lay the foundation for the development of breeding programmes in Norway and could demonstrate the macroalgae producers in Norway the possibility of establishing aquaculture in fjords.
Vitenskapelig – High-value compound induction by flashing light in Diacronema lutheri and Tetraselmis striata CTP4
Lisa M. Schüler, Juline Walter, Hidehiko Kato, ...
ForfattereLisa M. Schüler Juline Walter Hidehiko Kato Hirono Suzuki Christopher Jonathan Hulatt Ralf Rautenberger Sofia Navalho Benjamin Schmid Joao Varela Kiron Viswanath Peter Simon Claus Schulze
Phototrophic microalgae use light to produce biomass and high-value compounds, such as pigments and polyunsaturated fatty acids (PUFA), for food and feed. These biomolecules can be induced by flashing light during the final growth stage. We tested different exposure times (1–6 days) of flashing light (f = 0.5, 5, 50 Hz; duty cycle = 0.05) on biomass, pigment and fatty acid productivity in Diacronema lutheri and Tetraselmis striata. A three-day exposure to low-frequency (5 Hz) flashing light successfully increased the production of fucoxanthin, diatoxanthin, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in D. lutheri up to 4.6-fold and of lutein, zeaxanthin and EPA in T. striata up to 1.3-fold compared to that of continuous light. Biomass productivity declined 2-fold for D. lutheri and remained similar for T. striata compared to that of continuous light. Thus, short-term treatments of flashing light may be promising for industrial algal production to increase biomass value.
Vitenskapelig – Rapid and accurate determination of protein content in North Atlantic seaweed by NIR and FTIR spectroscopies
Calle Niemi, Agnes Mols Mortensen, Ralf Rautenberger, ...
ForfattereCalle Niemi Agnes Mols Mortensen Ralf Rautenberger Böris Sanna Christina A Matsson András Gorzsás Francesco G. Gentili
Seaweed is considered a potentially sustainable source of protein for human consumption, and rapid, accurate methods for determining seaweed protein contents are needed. Seaweeds contain substances which interfere with common protein estimation methods however. The present study compares the Lowry and BCA protein assays and protein determination by N-ratios to more novel spectroscopic methods. Linear regression of the height or the integrated area under the Amide II band of diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to predict seaweed protein with good prediction performance. Partial least squares regression (PLSR) was performed on both DRIFTS and near-infrared (NIR) spectra, with even higher prediction accuracy. Spectroscopy performed similar to or better than the calculated N-ratio of 4.14 for protein prediction. These spectral prediction methods require minimal sample preparation and chemical use, and are easy to perform, making them environmentally sustainable and economically viable for rapid estimation of seaweed protein.
Vitenskapelig – Improving fermentation of Saccharina latissima and Alaria esculenta silages with additives for preserving biomass and antioxidants
Ying Yen, Martin Riis Weisbjerg, Ralf Rautenberger, ...
ForfattereYing Yen Martin Riis Weisbjerg Ralf Rautenberger Adriána Fečkaninová Margarita Novoa-Garrido
Rapid deterioration of harvested macroalgal biomass is a challenge for macroalgal industry and can be overcome with the inexpensive ensiling preservation. To improve silage quality, Saccharina latissima and Alaria esculenta biomass was subjected to ensiling conditions following a 2 × 4 factorial design, with 2 prewilting treatments (no-prewilting and prewilted to 300 g DM kg−1 fresh biomass) and 4 additive treatments (no additive, formic acid, single and two species of Lactobacillus inoculant), and ensiled for 3 or 12 months at 15 °C. Acetate was the main fermentation product in these seaweed silages. Prewilting reduced the acetate, mannitol, and NH3 content in silages. In S. latissima silages without additives, prewilting led to less acidification (pH = 5.7). Also, prewilting caused protein and phlorotannin degradation. When treated with formic acid, the silage pH was below 4 regardless of the biomass’s moisture content. The use of Lactobacillus spp. inoculants was essential for lactate production in seaweed silages, and it significantly lowered silage pH in S. latissima and prewilted A. esculenta compared to silages with no additives. A high level of the phlorotannin content was preserved (> 90%) in the 3-month A. esculenta silages without prewilting. However, major reduction of antioxidant activity was observed in 12-month silages in both seaweed species. In conclusion, ensiling is a viable method for preserving Alaria and Saccharina biomass. Prewilting restricted silage fermentation, and both formic acid and bacterial additives facilitated silage acidification. However, there was no clear benefit of these treatments in preserving the antioxidant activity.
Foredrag – Phlorotannin content and antioxidant activity in Saccharina latissima and Alaria esculenta preserved by ensiling
Ying Yen, Ralf Rautenberger, Martin Riis Weisbjerg, ...
ForfattereYing Yen Ralf Rautenberger Martin Riis Weisbjerg Adriána Fečkaninová Margarita Novoa-Garrido
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Vitenskapelig – Priming of marine macrophytes for enhanced restoration success and food security in future oceans
Alexander Jüterbock, Antoine J. P. Minne, J. Mark Cock, ...
ForfattereAlexander Jüterbock Antoine J. P. Minne J. Mark Cock Melinda Ann Coleman Thomas Wernberg Lydia Scheschonk Ralf Rautenberger Jie Zhang Zi-Min Hu
Marine macrophytes, including seagrasses and macroalgae, form the basis of diverse and productive coastal ecosystems that deliver important ecosystem services. Moreover, western countries increasingly recognize macroalgae, traditionally cultivated in Asia, as targets for a new bio-economy that can be both economically profitable and environmentally sustainable. However, seagrass meadows and macroalgal forests are threatened by a variety of anthropogenic stressors. Most notably, rising temperatures and marine heatwaves are already devastating these ecosystems around the globe, and are likely to compromise profitability and production security of macroalgal farming in the near future. Recent studies show that seagrass and macroalgae can become less susceptible to heat events once they have been primed with heat stress. Priming is a common technique in crop agriculture in which plants acquire a stress memory that enhances performance under a second stress exposure. Molecular mechanisms underlying thermal priming are likely to include epigenetic mechanisms that switch state and permanently trigger stress-preventive genes after the first stress exposure. Priming may have considerable potential for both ecosystem restoration and macroalgae farming to immediately improve performance and stress resistance and, thus, to enhance restoration success and production security under environmental challenges. However, priming methodology cannot be simply transferred from terrestrial crops to marine macrophytes. We present first insights into the formation of stress memories in both seagrasses and macroalgae, and research gaps that need to be filled before priming can be established as new bio-engineering technique in these ecologically and economically important marine primary producers.
Foredrag – Effects of germanium dioxide (GeO2) as diatom growth inhibitor on the photophysiology and biomass production of the green marine macroalga Ulva fenestrata
The commercial cultivation of marine macroalgae is a young and rapidly growing industry sector in Norway. Although it is currently limited to a few brown macroalgae, other species such as the green marine macroalga Ulva fenestrata (formerly Ulva lactuca) has also a high potential for an industrial biomass production, for example to be used for the food marked. However, this process is strongly affected by the presence of marine diatoms transported along with the seawater into the cultivation system of U. fenestrata. These diatoms not only proliferate in the water tanks, they also colonise the green macroalgal biomass with many brown spots, which reduces its value for the food marked significantly. This presentation shows the results of a project that studied the use of germanium dioxide (GeO2) as a known growth inhibitor of diatoms to control their contamination during the biomass production process of U. fenestrata. First, the co-occurring diatom was morphologically identified as Fragilaria sp. using light microscopy. Thereafter, a dose-response experiment was conducted to reveal the concentrations of GeO2, resulting in an effective growth inhibition of Fragilaria sp. Based on this knowledge, the impact of different GeO2 concentrations was studied on how the photophysiolgy (photosynthetic characteristics, pigment patterns) and growth of U. fenestrata are affected in both small-scale (2 L) and large-scale (100 L) cultivation systems. An effective control of the proliferation of Fragilaria sp. during the cultivation process of U. fenestrata may result in the production a high-quality biomass with a high value for the food marked.
Vitenskapelig – Flashing light emitting diodes (LEDs) induce proteins, polyunsaturated fatty acids and pigments in three microalgae
Serena Lima, Peter Simon Claus Schulze, Lisa M. Schüler, ...
ForfattereSerena Lima Peter Simon Claus Schulze Lisa M. Schüler Ralf Rautenberger Daniela Morales-Sanchez Tamára F. Santos Hugo Pereira João C.S. Varela Francesca Scargiali Rene Hubertus Wijffels Viswanath Kiron
As the periodic emission of light pulses by light emitting diodes (LEDs) is known to stimulate growth or induce high value biocompounds in microalgae, this flashing light regime was tested on growth and biochemical composition of the microalgae Nannochloropsis gaditana, Koliella antarctica and Tetraselmis chui. At low flashing light frequencies (e.g., 5 and 50 Hz, Duty cycle = 0.05), a strain-dependent growth inhibition and an accumulation of protein, polyunsaturated fatty acids, chlorophyll or carotenoids (lutein, β-carotene, violaxanthin and neoxanthin) was observed. In addition, a 4-day application of low-frequency flashing light to concentrated cultures increased productivities of eicosapentaenoic acid (EPA) and specific carotenoids up to three-fold compared to continuous or high frequency flashing light (500 Hz, Duty cycle = 0.05). Therefore, applying low-frequency flashing light as finishing step in industrial production can increase protein, polyunsaturated fatty acids or pigment contents in biomass, leading to high-value algal products.
Foredrag – Factors influencing the biomass production of the green macroalga Ulva fenestrata from the high latitudes in North Norway and its use for a pre-commercial application
Vitenskapelig – Flashing light does not improve photosynthetic performance and growth of green microalgae
Peter Simon Claus Schulze, Celeste Brindley, José M. Fernández, ...
ForfatterePeter Simon Claus Schulze Celeste Brindley José M. Fernández Ralf Rautenberger Hugo Pereira Rene Hubertus Wijffels Viswanath Kiron
Light attenuation in photobioreactors is a major bottleneck in microalgal production. A possible strategy for artificial light-based microalgal production to deliver light deep inside the culture is through the periodical emission of high intensity light flashes (so-called flashing light). However, our results did not show improved photosynthetic rates compared to continuous light for dilute and concentrated Tetraselmis chui cultures exposed to flashing light with various repetition rates (frequencies 0.01 Hz–1 MHz), light-dark ratios (duty cycles: 0.001–0.7) or time-averaged light intensity (50–1000 μmol s−1 m−2). Likewise, flashing light applied to Chlorella stigmatophora and T. chui batch cultures could not enhance growth. However, we observed flashing light effects at different duty cycles and frequencies, depending on cell acclimation, culture concentration, and light intensity. In conclusion, artificial flashing light does not improve microalgal biomass productivities in photobioreactors, but low frequencies (f < 50 Hz) may be still used to improve light harvesting-associated biomolecules production.
Foredrag – Growth and photo-physiological responses of the green marine macroalga Ulva lactuca to light-emitting diodes (LEDs) and fluorescence light
Vitenskapelig – Interaction of Photoprotective and Acclimation Mechanisms in Ulva rigida (Chlorophyta) in Response to Diurnal Changes in Solar Radiation in Southern Chile
Edgardo Cruces, Ralf Rautenberger, Víctor Mauricio Cubillos, ...
ForfattereEdgardo Cruces Ralf Rautenberger Víctor Mauricio Cubillos Eduardo Ramírez‐Kushel Yesenia Rojas‐Lillo Carlos Lara Jaime Andrés Montory Iván Gómez
Species of the genus Ulva (Chlorophyta) are regarded as opportunistic organisms, which efficiently adjust their metabolism to the prevailing environmental conditions. In this study changes in chlorophyll‐a fluorescence‐based photoinhibition of photosynthesis, electron transport rates, photosynthetic pigments, lipid peroxidation, total phenolic compounds and antioxidant metabolism were investigated during a diurnal cycle of natural solar radiation in summer (for 12 h) under two treatments: photosynthetically active radiation (PAR: 400‐700 nm) and PAR+ ultraviolet (UV) radiation (280‐700 nm). In presence of PAR alone, Ulva rigida showed dynamic photoinhibition, and photosynthetic parameters and pigment concentrations decreased with the intensification of the radiation. On the other hand, under PAR+UV condition a substantial decline up to 43% was detected and an incomplete fluorescence recovery, also, P‐I curve values remained low in relation to the initial condition. The phenolic compounds increased their concentration only in UV radiation treatments without showing a correlation with the antioxidant activity. SOD and APX activities increased over 2‐fold respect at initial values during the onset of light intensity. In contrast, CAT increased its activity rapidly in response to the radiation stress to reach maxima at 10:00 h and decreasing during solar. The present study suggests that U. rigida is capability to acclimate to natural radiation stress relies on a concerted action of various physiological mechanisms that act at different times of the day and under different levels of environmental stress.
Poster – Photophysiology and growth of Ulva lactuca (Chlorophyta) under light-emitting diodes (LEDs) as potential new light sources in comparison to the traditionally-used fluorescence light
Ralf Rautenberger, Peter Simon Claus Schulze
Vitenskapelig – Carbonic anhydrase activity in seaweeds: overview and recommendations for measuring activity with an electrometric method, using Macrocystis pyrifera as a model species
Pamela A. Fernández, Michael Roleda, Ralf Rautenberger, ...
ForfatterePamela A. Fernández Michael Roleda Ralf Rautenberger Catriona L. Hurd
Carbonic anhydrase (CA) plays an important physiological role in all biological systems by accelerating the interconversion of CO2 and HCO3 −. In algae, CA is essential for photosynthesis: external CA (CAext) dehydrates HCO3 −, enhancing the supply of CO2 to the cell surface, and internal CA (CAint) interconverts HCO3 − and CO2 to maintain the inorganic carbon (Ci) pool and supply CO2 to RuBisCO. We frst conducted a literature review comparing the conditions in which CA extraction and measurement have been carried out, using the commonly used Wilbur–Anderson method. We found that the assay has been widely modifed since its introduction in 1948, mostly without being optimized for the species tested. Based on the review, an optimized protocol for measuring CA in Macrocystis pyrifera was developed, which showed that the assay conditions can strongly afect CA activity. Tris–HCl bufer gave the highest levels of CA activity, but phosphate bufer reduced activity signifcantly. Bufers containing polyvinylpyrrolidone (PVP) and dithiothreitol (DTT) stabilized CA. Using the optimized assay, CAext and CAint activities were readily measured in Macrocystis with higher precision compared to the non-optimized method. The CAint activity was 2×higher than CAext, which is attributed to the Ci uptake mechanisms of Macrocystis. This study suggests that the CA assay needs to be optimized for each species prior to experimental work to obtain both accurate and precise results.
Foredrag – Variations in heavy metals, polyphenols and iodine contents in commercially important and edible seaweeds
Ralf Rautenberger, Stig A. Borgvang