| 1. |
- Abreu, Ilka, et al.
(författare)
-
Changes in lipid and carotenoid metabolism in Chlamydomonas reinhardtii during induction of CO2-concentrating mechanism : Cellular response to low CO2 stress
- 2020
-
Ingår i: Algal Research. - : Elsevier. - 2211-9264. ; 52
-
Tidskriftsartikel (refereegranskat)abstract
- Photosynthetic organisms strictly depend on CO2 availability and the CO2:O2 ratio, as both CO2/O2 compete for catalytic site of Rubisco. Green alga Chlamydomonas reinhardtii, can overcome CO2 shortage by inducing CO2-concentrating mechanism (CCM). Cells transferred to low-CO2 are subjected to light-driven oxidative stress due to decrease in the electron sink. Response to environmental perturbations is mediated to some extent by changes in the lipid and carotenoid metabolism. We thus hypothesize that when cells are challenged with changes in CO2 availability, changes in the lipidome and carotenoids profile occur. These changes expected to be transient, when CCM is activated, CO2 limitation will be substantially ameliorated. In our experiments, cells were transferred from high (5%) to low (air equilibrium) CO2. qPCR analysis of genes related to CCM and lipid metabolism was carried out. Lipidome was analyzed both in whole cells and in isolated lipid droplets. We characterized the changes in polar lipids, fatty acids and ketocarotenoids. In general, polar lipids significantly and transiently increased in lipid droplets during CCM. Similar pattern was observed for xanthophylls, ketocarotenoids and their esters. The data supports our hypothesis about the roles of lipids and carotenoids in tackling the oxidative stress associated with acclimation to sub-saturating CO2.
|
|
| 2. |
- Albers, Eva, 1966, et al.
(författare)
-
Influence of preservation methods on biochemical composition and downstream processing of cultivated Saccharina latissima biomass
- 2021
-
Ingår i: Algal Research. - : Elsevier BV. - 2211-9264. ; 55
-
Tidskriftsartikel (refereegranskat)abstract
- Saccharina latissima biomass cultivated along the Swedish west coast was subjected to four different scalable preservation methods after harvest; freezing, sun-drying, oven-drying and ensiling. Freeze-drying and freezing at -80 ?C were also included to provide dry and wet references. The effects of the different preservation methods on the composition of Saccharina biomass (on dry weight, DW, basis), and the recovery as well as properties of high-quality protein, alginate and biogas were evaluated. Sun-drying significantly reduced protein, alginate and fatty acid content of the seaweeds and thereby concentrated ash in the biomass compared to the other methods. Protein/amino acids and fatty acids were significantly concentrated in ensiled biomass, while mannitol and laminarin were reduced compared to the other biomasses. Oven-drying and -20 ?C freezing affected the composition the least, with lower ash content and alterations in some specific amino and fatty acids. Sun-drying and ensiling resulted in significantly lower protein solubility at high pH compared to the other biomasses which translated into the lowest total seaweed protein recovery using the pH-shift process. Highest protein yield was obtained with the freeze-dried reference. Ensiling lead to a significant decrease in the molecular weight of alginate, while sun-drying caused a negative effect on alginate by inducing a shift in the guluronic and mannuronic acids composition of alginate. Sun-drying gave the lowest methane yield in the anaerobic digestion experiments while freezing at -80 ?C gave the highest yield, closely followed by freezing at -20 ?C and ensiling. To conclude, preservation methods must be carefully chosen to protect the valuable component in Saccharina latissima, and to achieve an efficient downstream processing ultimately yielding high quality products as part of a seaweed biorefinery.
|
|
| 3. |
- Arena, Rosaria, et al.
(författare)
-
Cultivation and biochemical characterization of isolated Sicilian microalgal species in salt and temperature stress conditions
- 2021
-
Ingår i: Algal Research. - : Elsevier BV. - 2211-9264. ; 59
-
Tidskriftsartikel (refereegranskat)abstract
- In the last years, the possibility to exploit autochthone microalgae in regional applications has been explored. The regional-based microalgal industry may bring several benefits, as autochthone microalgae are already adapted to the biotic and abiotic stresses of their environment. In this work, this concept was applied to Sicily, in which three microalgal strains were collected from the coastline. Monoalgal strains were then isolated and molecular characterization was performed for the species determination. Three of them, two strains of Chlorella and one of Dunaliella, were cultivated in lab-scale in four different conditions: Low Temperature-Low Salt (LT-LS), High-Temperature-Low Salt (HT-LS), Low Temperature-High Salt (LT-HS) and High Temperature-High Salt (HT-HS) to investigate the role of each condition on the growth performance, the productivity and the biochemical composition of the microalgal biomass. In particular, lipid, fatty acid composition and antioxidant capacity were assessed. Results indicated that one of the Sicilian strains of Chlorella has a better growth performance at a higher temperature while the Dunaliella strain is tolerant to high-salt stress. Moreover, the biochemical composition appears to be strongly influenced by temperature and salt stresses: the lipid content decreased in all the strains and a significant shift in fatty acid composition was observed, with an increase in the content of n-3 PUFAs in some cases. Results indicated that also the carotenoids content decreased in some of the tested stress conditions. The results obtained in this research represent a first step for developing a regional-based microalgal industry in Sicily by exploiting the natural biodiversity of the Sicilian environment.
|
|
| 4. |
- Arias, Carolina, et al.
(författare)
-
Nuclear proteome analysis of Chlamydomonas with response to CO2 limitation
- 2020
-
Ingår i: Algal Research. - : Elsevier. - 2211-9264. ; 46
-
Tidskriftsartikel (refereegranskat)abstract
- Chlamydomonas reinhardtii is a unicellular green alga that can survive at a wide range of inorganic carbon (Ci) concentrations by regulating the activity of a CO2-concentrating mechanism (CCM) as well as other cellular functions. Under CO2 limited conditions, C. reinhardtii cells display a wide range of adaptive responses including changes in photosynthetic electron transport, mitochondria localization in the cells, the structure of the pyrenoid starch sheath, and primary metabolism. In addition to these functional and structural changes, gene and protein expression are also affected. Several physiological aspects of the CO2 response mechanism have been studied in detail. However, the regulatory components (transcription factors and transcriptional regulators) involved in this process are not fully characterized. Here we report a comprehensive analysis of the C. reinhardtii nuclear proteome using liquid chromatography electrospray ionization spectrometry (LC-ESI-MS). The study aims to identify the proteins that govern adaptation to varying CO2 concentrations in Chlamydomonas. The nuclear proteome of C. reinhardtii cells grown in the air at high (5%) and low (0.04%) CO2 concentrations were analyzed. Using this approach, we identified 1378 proteins in total, including 90 putative transcription factors and 27 transcriptional regulators. Characterization of these new regulatory components could shed light on the molecular mechanisms underlying acclimation to CO2 stress.
|
|
| 5. |
- Cavonius, Lillie, 1981, et al.
(författare)
-
pH-shift processing of Nannochloropsis oculata microalgal biomass to obtain a protein-enriched food or feed ingredient
- 2015
-
Ingår i: Algal Research. - : Elsevier BV. - 2211-9264. ; 11, s. 95-102
-
Tidskriftsartikel (refereegranskat)abstract
- Fractionation of plant and animal raw materials by pH-shift processing has been widely applied to purify proteins. The principle is to solubilize proteins at high or low pH, removing debris and precipitating the proteins near their isoelectric point. We here describe the pH-shift process on commercially available Nannochloropsis oculata. The partitioning of major nutrients into the various fractions of the process was studied. Proteins were found to exhibit maximal solubility between pH 7 and 10, with a minimal solubility below pH 4. Two process versions were investigated in this study, with solubilization at either pH 7 (native pH) or 10; both versions were precipitated at pH 3. Up to 85% of both the protein and total fatty acids were recovered in the final product, compared to the initial algal slurry. Protein, total fatty acids and carbohydrates were concentrated in the final product, while the ash content was lower compared to the starting material. From a processing point of view, solubilization of Nannochloropsis at native pH was found to be preferable, since less chemicals were consumed compared to high-pH solubilization. Owing to its content of protein and (total) fatty acids (23 and 12% of dry weight, respectively), the latter enriched in eicosapentaenoic acid (EPA), the product of the pH-shift process has potential as a functional food ingredient.
|
|
| 6. |
- Cheregi, Otilia, et al.
(författare)
-
Transcriptome analysis reveals insights into adaptive responses of two marine microalgae species to Nordic seasons
- 2023
-
Ingår i: Algal Research. - 2211-9264. ; 74
-
Tidskriftsartikel (refereegranskat)abstract
- There is an increasing interest in algae-based biomass produced outdoors in natural and industrial settings for biotechnological applications. To predict the yield and biochemical composition of the biomass, it is important to understand how the transcriptome of species and strains of interest is affected by seasonal changes. Here we studied the effects of Nordic winter and summer on the transcriptome of two phytoplankton species, namely the diatom Skeletonema marinoi (Sm) and the eustigmatophyte Nannochloropsis granulata (Ng), recently identified as potentially important for biomass production on the west coast of Sweden. Cultures were grown in photobioreactors in simulated Nordic summer and winter, and the gene expression in two phases was quantified by Illumina RNA-sequencing. Five paired comparisons were made among the four conditions. Sm was overall more responsive to seasons since 70 % of the total transcriptome (14,783 genes) showed differential expression in at least one comparison as compared to 1.6 % (1403 genes) for Ng. For both species, we observed larger differences between the seasons than between the phases of the same season. In summer phase 1, Sm cells focused on photosynthesis and polysaccharide biosynthesis. Nitrate assimilation and recycling of intracellular nitrogen for protein biosynthesis were more active in summer phase 2 and throughout winter. Lipid catabolism was upregulated in winter relative to summer to supply carbon for respiration. Ng favored lipid accumulation in summer, while in winter activated different lipid remodeling pathways as compared to Sm. To cope with winter, Ng upregulated breakdown and transport of carbohydrates for energy production. Taken together, our transcriptome data reveal insights into adaptive seasonal responses of Sm and Ng important for biotechnological applications on the west coast of Sweden, but more work is required to decipher the molecular mechanisms behind these responses.
|
|
| 7. |
- Durall de la Fuente, Claudia, et al.
(författare)
-
Enhanced growth at low light intensity in the cyanobacterium Synechocystis PCC 6803 by overexpressing phosphoenolpyruvate carboxylase
- 2016
-
Ingår i: Algal Research. - : Elsevier BV. - 2211-9264. ; 16, s. 275-281
-
Tidskriftsartikel (refereegranskat)abstract
- Synechocystis PCC 6803 strains overexpressing pepc, gene encoding the carbon fixing enzyme phosphoenolpyruvate carboxylase (PEPc), were constructed and characterized for growth, PEPc protein content and in vitro PEPc activities. Synechocystis strains WT + Km(r) - one (native) copy of pepc (control), WT + 2xPEPc - native copy of pepc and two additional native copies of pepc (in total three copies of pepc), and WT + PPM - native copies of ppsa (encoding phosphoenolpyruvate synthase), pepc and mdh (encoding malate dehydrogenase) and one additional copy of each gene (in total two copies each of ppsa, pepc and mdh) were analyzed for growth under normal and low light intensities, and in darkness (no growth). No significant differences in the growth rates were observed when the cells were grown under normal light intensity. However, growth under low light intensity (3 mu mol photons.m(-2).sec(-1)) resulted in increased growth rate, in particular in the strain with 3 copies of pepc. SDS-PAGE/Western immunoblots using antibodies directed against PEPc demonstrated an increased level of PEPc protein with increasing number of copies of pepc. This was followed by increased levels of in vitro PEPc activities. A less efficient ribulose 1,5-bisphosphate carboxylase/oxygenase in combination with reduced levels of NADPH and ATP under low light condition may make the relatively more efficient carbon fixing enzyme PEPc the limiting step for growth under this condition.
|
|
| 8. |
- Durall de la Fuente, Claudia, et al.
(författare)
-
Mechanisms of carbon fixation and engineering for increased carbon fixation in cyanobacteria
- 2015
-
Ingår i: Algal Research. - : Elsevier BV. - 2211-9264. ; 11, s. 263-270
-
Forskningsöversikt (refereegranskat)abstract
- Cyanobacteria, gram-negative prokaryotic microorganisms, perform oxygenic photosynthesis with a photosynthetic machinery similar to higher plants which includes ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) as the main CO2-fixing enzyme. Currently, there is a growing interest to use cyanobacteria as photosynthetic microbial cell factories for the direct production of solar fuels or other compounds of human interest. However, rates and efficiencies to produce e.g. biofuels are still very low. The amount of available fixed carbon for the synthesis of desired product(s) may be one of the limiting steps. This contribution reviews CO2-fixation in cyanobacteria with focus on CO2-concentrating mechanisms, RuBisCO, phosphoenolpyruvate carboxylase and other carboxylases, engineering approaches for increased carbon fixation, and finally the synthetic malonyl-CoA-oxaloacetate-glyoxylate pathways.
|
|
| 9. |
- Ekendahl, Susanne, et al.
(författare)
-
Energy-efficient outdoor cultivation of oleaginous microalgae at northern latitudes using waste heat and flue gas from a pulp and paper mill
- 2018
-
Ingår i: Algal Research. - : Elsevier BV. - 2211-9264. ; 31, s. 138-146
-
Tidskriftsartikel (refereegranskat)abstract
- Energy efficient cultivation is the major bottleneck for microalgal biomass production on a large scale and considered very difficult to attain at northern latitudes. In this study an unconventional method for industrial microalgae cultivation for bio-oil production using pulp and paper mill waste resources while harvesting only once a year was performed, mainly in order to investigate the energy efficiency of the process. Algae were cultivated for three months in 2014 in covered pond systems with access to flue gas and waste heat from the industry, and the biomass was recovered as thick sediment sludge after dewatering. The cultivation systems, designed to manage the waste resources, reached a promising photosynthetic efficiency of at most 1.1%, a net energy ratio (NER) of 0.25, and a projected year-round energy biomass yield per area 5.2 times higher than corresponding rapeseed production at the location. Thus, microalgae cultivation was, for the first time, proven energy efficient in a cold continental climate. Energy-rich indigenous communities quickly out-competed the oleaginous monocultures used for inoculation. The recovered biomass had higher heating values of 20–23 MJ kg− 1 and contained 14–19% oil dominated by C16 followed by C18 fatty acids. The cultivation season at 59°15′N, 14°18′E was projected to be efficient for 10 months and waste heat drying of the biomass is suggested for two winter months. The technique is proposed for carbon sequestering and energy storage in the form of microalgal sludge or dry matter for later conversion into biochemicals.
|
|
| 10. |
- Ekman Nilsson, Anna, et al.
(författare)
-
Life cycle assessment of a seaweed-based biorefinery concept for production of food, materials, and energy
- 2022
-
Ingår i: Algal Research. - : Elsevier B.V.. - 2211-9264. ; 65
-
Tidskriftsartikel (refereegranskat)abstract
- Blue Economy is seen as an essential contributor to a sustainable development, and it is an important part of the EU Green Deal. Seaweed plays a key role in the Blue Economy as a source of food, feed, and feedstock for biorefineries. Today, the largest part of global seaweed production is based in Asia, but there is also a growing interest in seaweed production in Europe. However, more knowledge on the environmental impacts is needed to ensure sustainable growth of the sector. Seaweed can be used in biorefineries to produce a variety of products for food and non-food applications. The aim of this paper was to perform a life cycle assessment (LCA) of a seaweed value-chain, including seaweed cultivation and production into sodium alginate, biodegradable materials, biogas, and fertilizer in a biorefinery setting. The LCA included 19 environmental impact categories but focused on climate change. The seaweed Saccharina latissima was cultivated and processed in Ireland. Sodium alginate was then extracted by means of ultrasound-assisted extraction, a novel extraction technology. Cellulosic residues produced after the extraction were used for the production of films used as a packaging material. Residues that remain after the production of the films were sent to anaerobic digestion to achieve a no-waste concept. For seaweed cultivation, fuel use and drying of seaweed biomass were the main environmental hot spots; and for the alginate extraction process, the yield and purification after extraction were the main hot spots. Overall, the results of this paper showed that the seaweed-based biorefinery has the potential to be sustainable, but several improvements are necessary before it is competitive with land-based systems. © 2022 The Authors
|
|
