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Spain, O. & Funk, C. (2024). A step towards more eco-friendly and efficient microalgal harvesting: Inducing flocculation in the non-naturally flocculating strain chlorella vulgaris (13-1) without chemical additives. Algal Research, 79, Article ID 103450.
Open this publication in new window or tab >>A step towards more eco-friendly and efficient microalgal harvesting: Inducing flocculation in the non-naturally flocculating strain chlorella vulgaris (13-1) without chemical additives
2024 (English)In: Algal Research, ISSN 2211-9264, Vol. 79, article id 103450Article in journal (Refereed) Published
Abstract [en]

Flocculation is often regarded as a cost-effective and reliable method for microalgal harvesting. However, the traditional method often requires the addition of chemical agents to induce flocculation. This carries certain disadvantages including the chemical contamination of the biomass and the subsequent need to remove the flocculants from the medium. To address these issues, this study aimed to induce flocculation in a naturally non-flocculating strain (Chlorella vulgaris 13-1) without resorting to chemical additives, with the ultimate goal of increasing harvesting efficiency. Scanning electron microscopy showed that Scotelliopsis reticulata UFA-2, a naturally flocculating strain, produces extracellular polymeric substances (EPS) whereas 13-1 does not. As a result, two methods were used to induce flocculation in 13-1: co-cultivation of UFA-2 and 13-1, and insertion of EPS produced by UFA-2 into the growth medium of 13-1. The co-cultivation of 13-1 with UFA-2 significantly increased the flocculation efficiency compared to that of 13-1 alone (30 % higher flocculation efficiency after one hour of settling and 52 % higher after three hours of settling). Alternatively, the insertion of dry tightly-bound (TB) UFA-2 EPS into 13-1 cultures also improved flocculation efficiency (by 19 % compared to the control), while addition of soluble or loosely-bound (LB) EPS was less efficient (less than 1 % and 10 %, respectively). FTIR results showed that the composition of TB-EPS was different to that of LB and soluble EPS. TB-EPS contained higher proportions of proteins and different types of carbohydrates, potentially contributing to its increased efficacy in inducing flocculation in microalgae.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Cell wall, Extracellular polymeric substances, Flocculation, Harvesting, Microalgae
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-222219 (URN)10.1016/j.algal.2024.103450 (DOI)2-s2.0-85186696607 (Scopus ID)
Available from: 2024-03-14 Created: 2024-03-14 Last updated: 2024-03-14Bibliographically approved
Mohammadkhani, G., Mahboubi, A., Plöhn, M., Funk, C. & Ylitervo, P. (2024). The potential of Nordic microalgae in nutrient removal from anaerobic digestion effluents. Physiologia Plantarum, 176(1), Article ID e14153.
Open this publication in new window or tab >>The potential of Nordic microalgae in nutrient removal from anaerobic digestion effluents
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2024 (English)In: Physiologia Plantarum, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 176, no 1, article id e14153Article in journal (Refereed) Published
Abstract [en]

Anaerobic digestion is a promising method for organic waste treatment. While the obtained digestate can function as fertilizer, the liquid fraction produced is rather problematic to discharge due to its high nitrogen and chemical oxygen demand contents. Microalgae have great potential in sustainable nutrient removal from wastewater. This study aimed at evaluating native Swedish microalgae cultivation (batch operation mode, 25°C and continuous light of 80 μmol m−2 s−1) on anaerobic digestion effluent of pulp and paper sludge (PPS) or chicken manure (CKM) to remove ammonium and volatile fatty acids (VFAs). While algal strains, Chlorella vulgaris, Chlorococcum sp., Coelastrella sp., Scotiellopsis reticulata and Desmodesmus sp., could assimilate VFAs as carbon source, acetic acid was the most preferred. Higher algal biomass and cell densities were achieved using PPS compared to CKM. In PPS, Coelastrella sp. and Chlorella vulgaris reached the highest cell densities after 15 days, about 79 × 106 and 43 × 106 cells mL−1, respectively. Although in PPS, ammonium was completely assimilated (195 mg L−1), this was only 46% (172 mg L−1) in CKM. Coelastrella sp. produced the highest biomass concentration independently of the medium (1.84 g L−1 in PPS and 1.99 g L−1 in CKM). This strain is a promising candidate for nutrient removal and biomass production in the aforementioned media, followed by Chlorella vulgaris and Chlorococcum sp. They have great potential to reduce the environmental impact of industrial anaerobic digestion effluents in Nordic countries.

Place, publisher, year, edition, pages
John Wiley & Sons, 2024
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-219500 (URN)10.1111/ppl.14153 (DOI)001134340600001 ()2-s2.0-85181494300 (Scopus ID)
Funder
Swedish Research Council, 2019–00492Bio4EnergyUmeå University
Available from: 2024-01-24 Created: 2024-01-24 Last updated: 2024-01-24Bibliographically approved
Mehariya, S., Plöhn, M., Jablonski, P., Stagge, S., Jönsson, L. J. & Funk, C. (2023). Biopolymer production from biomass produced by Nordic microalgae grown in wastewater. Bioresource Technology, 376, Article ID 128901.
Open this publication in new window or tab >>Biopolymer production from biomass produced by Nordic microalgae grown in wastewater
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2023 (English)In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 376, article id 128901Article in journal (Refereed) Published
Abstract [en]

Biomass from four different Nordic microalgal species, grown in BG-11 medium or synthetic wastewater (SWW), was explored as inexpensive carbohydrate-rich feedstock for polyhydroxybutyrate (PHB) production via microbial fermentation. Thermochemical pre-treatment (acid treatment followed by autoclavation) with 2% hydrochloric acid or 1% sulphuric acid (v/v) was used to maximize sugar yield prior to fermentation. Pre-treatment resulted in ∼5-fold higher sugar yield compared to the control. The sugar-rich hydrolysate was used as carbon source for the PHB-producing extremophilic bacterium Halomonas halophila. Maximal PHB production was achieved with hydrolysate of Chlorococcum sp. (MC-1) grown on BG-11 medium (0.27 ± 0.05 g PHB/ g DW), followed by hydrolysate derived from Desmodesmus sp. (RUC-2) grown on SWW (0.24 ± 0.05 g PHB/ g DW). Nordic microalgal biomass grown on wastewater therefore can be used as cheap feedstock for sustainable bioplastic production. This research highlights the potential of Nordic microalgae to develop a biobased economy.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Bioeconomy, Bioplastic, Nordic microalgae, Polyhydroxybutyrate, Pre-treatment, Wastewater
National Category
Microbiology Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-206016 (URN)10.1016/j.biortech.2023.128901 (DOI)2-s2.0-85150186738 (Scopus ID)
Funder
Swedish Research Council Formas, 2019-00492Bio4EnergyNordForsk, 82845Umeå University
Available from: 2023-03-28 Created: 2023-03-28 Last updated: 2024-02-20Bibliographically approved
León-Vaz, A., Cubero-Cardoso, J., Trujillo-Reyes, Á., Fermoso, F. G., León, R., Funk, C., . . . Urbano, J. (2023). Enhanced wastewater bioremediation by a sulfur-based copolymer as scaffold for microalgae immobilization (AlgaPol). Chemosphere, 315, Article ID 137761.
Open this publication in new window or tab >>Enhanced wastewater bioremediation by a sulfur-based copolymer as scaffold for microalgae immobilization (AlgaPol)
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2023 (English)In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 315, article id 137761Article in journal (Refereed) Published
Abstract [en]

In recent years, there has been an increasing concern related to the contamination of aqueous ecosystems by heavy metals, highlighting the need to improve the current techniques for remediation. This work intends to address the problem of removing heavy metals from waterbodies by combining two complementary methodologies: adsorption to a copolymer synthesized by inverse vulcanization of sulfur and vegetable oils and phytoremediation by the microalga Chlorella sorokiniana to enhance the metal adsorption. After studying the tolerance and growth of Chlorella sorokiniana in the presence of the copolymer, the adsorption of highly concentrated Cd2+ (50 mg L−1) by the copolymer and microalgae on their own and the combined immobilized system (AlgaPol) was compared. Additionally, adsorption studies have been performed on mixtures of the heavy metals Cd2+ and Cu2+ at a concentration of 8 mg L−1 each. AlgaPol biofilm is able to remove these metals from the growth medium by more than 90%. The excellent metal adsorption capacity of this biofilm can be kinetically described by a pseudo-second-order model.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Biofilm, Chlorella sorokiniana, Heavy metal, Inverse vulcanization, Kinetics, Sustainability
National Category
Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-203548 (URN)10.1016/j.chemosphere.2023.137761 (DOI)000955288800001 ()36610507 (PubMedID)2-s2.0-85145854385 (Scopus ID)
Funder
Swedish Research Council Formas, 2019-00492NordForsk, 82845Umeå University
Available from: 2023-01-19 Created: 2023-01-19 Last updated: 2023-09-05Bibliographically approved
León-Vaz, A., León, R., Vigara, J. & Funk, C. (2023). Exploring Nordic microalgae as a potential novel source of antioxidant and bioactive compounds. New Biotechnology, 73, 1-8
Open this publication in new window or tab >>Exploring Nordic microalgae as a potential novel source of antioxidant and bioactive compounds
2023 (English)In: New Biotechnology, ISSN 1871-6784, E-ISSN 1876-4347, Vol. 73, p. 1-8Article in journal (Refereed) Published
Abstract [en]

Nordic microalgae are a group of photosynthetic organisms acclimated to growth at low temperature and in varying light conditions; the subarctic climate offers bright days with moderate temperatures during summer and cold and dark winter months. The robustness to these natural stress conditions makes the species interesting for large-scale cultivation in harsh environments and for the production of high-value compounds. The aim of this study was to explore the ability of nineteen species of Nordic microalgae to produce different bioactive compounds, such as carotenoids or polyphenols. The results showed that some of these strains are able to produce high amounts of carotenoids (over 12 mg·g-1 dry weight) and phenolic compounds (over 20 mg GAE·g-1 dry weight). Based on these profiles, six species were selected for cultivation under high light and cold stress (500 μmol·m-2·s-1 and 10 ˚C). The strains Chlorococcum sp. (MC1) and Scenedesmus sp. (B2–2) exhibited similar values of biomass productivity under standard or stress conditions, but produced higher concentrations of carotenoids (an increase of 40% and 25%, respectively), phenolic compounds (an increase of 40% and 30%, respectively), and showed higher antioxidant capacity (an increase of 15% and 20%, respectively) during stress. The results highlight the ability of these Nordic microalgae as outstanding producers of bioactive compounds, justifying their cultivation at large scale in Nordic environments.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Carotenoids, Cold stress, DPPH, High light stress, High-value compounds, Phenolic compounds
National Category
Organic Chemistry
Identifiers
urn:nbn:se:umu:diva-201945 (URN)10.1016/j.nbt.2022.12.001 (DOI)000902092200001 ()2-s2.0-85143988597 (Scopus ID)
Funder
Swedish Research Council Formas, 2019-00492NordForsk, 82845
Available from: 2022-12-29 Created: 2022-12-29 Last updated: 2023-09-05Bibliographically approved
Alling, T., Funk, C. & Gentili, F. G. (2023). Nordic microalgae produce biostimulant for the germination of tomato and barley seeds. Scientific Reports, 13(1), Article ID 3509.
Open this publication in new window or tab >>Nordic microalgae produce biostimulant for the germination of tomato and barley seeds
2023 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 3509Article in journal (Refereed) Published
Abstract [en]

Microalgal biomass may have biostimulating effects on plants and seeds due to its phytohormonal content, and harnessing this biostimulating effect could contribute to sustainable agriculture. Two Nordic strains of freshwater microalgae species Chlorella vulgaris and Scenedesmus obliquus were each cultivated in a photobioreactor receiving untreated municipal wastewater. The algal biomass and the supernatant after algal cultivation were tested on tomato and barley seeds for biostimulating effects. Intact algal cells, broken cells, or harvest supernatant were applied to the seeds, and germination time, percentage and germination index were evaluated. Seeds treated with C. vulgaris, in particular intact cells or supernatant, had up to 25 percentage units higher germination percentage after 2 days and an overall significantly faster germination time (germinated on average between 0.5 and 1 day sooner) than seeds treated with S. obliquus or the control (water). The germination index was higher in C. vulgaris treatments than in the control for both tomato and barley, and this was observed for both broken and intact cells as well as supernatant. The Nordic strain of C. vulgaris cultivated in municipal wastewater thus shows potential for use as biostimulant in agriculture, adding novel economic and sustainability benefits.

Place, publisher, year, edition, pages
Nature Publishing Group, 2023
National Category
Botany Agricultural Science Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-205733 (URN)10.1038/s41598-023-30707-8 (DOI)36864186 (PubMedID)2-s2.0-85149330401 (Scopus ID)
Available from: 2023-03-16 Created: 2023-03-16 Last updated: 2023-03-16Bibliographically approved
Štrancar, V., van Midden, K. P., Krahn, D., Morimoto, K., Novinec, M., Funk, C., . . . van der Hoorn, R. A. .. (2022). Activity-based probes trap early active intermediates during metacaspase activation. iScience, 25(11), Article ID 105247.
Open this publication in new window or tab >>Activity-based probes trap early active intermediates during metacaspase activation
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2022 (English)In: iScience, E-ISSN 2589-0042 , Vol. 25, no 11, article id 105247Article in journal (Refereed) Published
Abstract [en]

Metacaspases are essential cysteine proteases present in plants, fungi, and protists that are regulated by calcium binding and proteolytic maturation through mechanisms not yet understood. Here, we developed and validated activity-based probes for the three main metacaspase types, and used them to study calcium-mediated activation of metacaspases from their precursors in vitro. By combining substrate-inspired tetrapeptide probes containing an acyloxymethylketone (AOMK) reactive group, with purified representatives of type-I, type-II, and type-III metacaspases, we were able to demonstrate that labeling of mature metacaspases is strictly dependent on calcium. The probe with the highest affinity for all metacaspases also labels higher molecular weight proteoforms of all three metacaspases only in the presence of calcium, displaying the active, unprocessed metacaspase intermediates. Our data suggest that metacaspase activation proceeds through previously unknown active intermediates that are formed upon calcium binding, before precursor processing.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Cell biology, Functional aspects of cell biology, Methodology in biological sciences
National Category
Plant Biotechnology
Identifiers
urn:nbn:se:umu:diva-200855 (URN)10.1016/j.isci.2022.105247 (DOI)000964036200001 ()2-s2.0-85140894507 (Scopus ID)
Available from: 2022-11-15 Created: 2022-11-15 Last updated: 2023-09-05Bibliographically approved
Spain, O. & Funk, C. (2022). Detailed Characterization of the Cell Wall Structure and Composition of Nordic Green Microalgae. Journal of Agricultural and Food Chemistry, 70(31), 9711-9721
Open this publication in new window or tab >>Detailed Characterization of the Cell Wall Structure and Composition of Nordic Green Microalgae
2022 (English)In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 70, no 31, p. 9711-9721Article in journal (Refereed) Published
Abstract [en]

Green microalgae are attractive to food, pharmaceutical, and biofuel industries due to the promising and diverse properties of their intracellular components. In current biotechnological applications, however, clear bottlenecks are the cell disruption and cell harvesting steps. Challenges in both of these processes are directly linked to the properties of the microalgal cell wall. The aim of this study was to explore the cell wall compositions and morphologies of four Nordic microalgal strains (Chlorella vulgaris (13-1), Scenedesmus sp. (B2-2), Haematococcus pluvialis, and Coelastrella sp. (3-4)) and their changes in relation to logarithmic and stationary growth phases. Transmission electron microscopy imaging enabled us to visualize the cell walls and to observe structural elements such as spines, microfibrillar hairs, or layers. Using cryogenic X-ray photoelectron spectroscopy, we quantified lipid, protein, and polysaccharide content of the outer surface of the microalgal cell wall in cultures. Fourier transform infrared spectroscopy highlighted changes between growth phases within the polysaccharide and protein fractions of the cell wall. Very prominent differences were observed in sugar and protein composition of the Scenedesmus sp. (B2-2) cell wall compared to the cell walls of the other three Nordic strains using trimethylsilyl derivatization.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2022
Keywords
cell wall, cryo-XPS, FTIR, imaging, microalgae
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-198732 (URN)10.1021/acs.jafc.2c02783 (DOI)000834288300001 ()35894177 (PubMedID)2-s2.0-85135768057 (Scopus ID)
Funder
NordForsk, 82845Swedish Research Council Formas, 2019-00492Bio4Energy, B4E3-TM-2-03
Available from: 2022-08-22 Created: 2022-08-22 Last updated: 2022-08-22Bibliographically approved
Štrancar, V., van Midden, K. P., Klemenčič, M. & Funk, C. (2022). Expression and purification of the type I metacaspase from a Cryptophyte Guillardia theta, GtMCA-I. In: Marina Klemenčič; Simon Stael; Pitter F. Huesgen (Ed.), Plant proteases and plant cell death: methods and protocols (pp. 1-11). Humana Press
Open this publication in new window or tab >>Expression and purification of the type I metacaspase from a Cryptophyte Guillardia theta, GtMCA-I
2022 (English)In: Plant proteases and plant cell death: methods and protocols / [ed] Marina Klemenčič; Simon Stael; Pitter F. Huesgen, Humana Press, 2022, , p. 11p. 1-11Chapter in book (Refereed)
Abstract [en]

Type I metacaspases are the most ubiquitous of the three metacaspase types and are present in representatives of prokaryotes, unicellular eukaryotes including yeasts, algae, and protozoa, as well as land plants. They are composed of two structural units: a catalytic so-called p20 domain with the His-Cys catalytic dyad and a regulatory p10 domain. Despite their structural homology to caspases, these proteases cleave their substrates after the positively charged amino acid residues at the P1 position, just like the metacaspases of type II and type III. We present a protocol for expression and purification of the only type I protease from a secondary endosymbiosis Guillardia theta, GtMCA-I by overexpression of its gene in BL21 (DE3) E. coli cells and one-day sequential purification using nickel-affinity, ion-exchange, and size-exclusion chromatography.

Place, publisher, year, edition, pages
Humana Press, 2022. p. 11
Series
Methods in Molecular Biology, ISSN 1064-3745, E-ISSN 1940-6029 ; 2447
Keywords
Algae, C14, Proteolysis, Regulated cell death, Trypsin-like
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-196176 (URN)10.1007/978-1-0716-2079-3_1 (DOI)2-s2.0-85130766806 (Scopus ID)9781071620786 (ISBN)9781071620793 (ISBN)
Available from: 2022-06-14 Created: 2022-06-14 Last updated: 2022-06-27Bibliographically approved
Sabljić, I., Zou, Y., Klemenčič, M., Funk, C., Ståhlberg, J. & Bozhkov, P. (2022). Expression and purification of the type II metacaspase from a unicellular green alga Chlamydomonas reinhardtii. In: Marina Klemenčič; Simon Stael; Pitter F. Huesgen (Ed.), Plant proteases and plant cell death: methods and protocols (pp. 13-20). Humana Press
Open this publication in new window or tab >>Expression and purification of the type II metacaspase from a unicellular green alga Chlamydomonas reinhardtii
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2022 (English)In: Plant proteases and plant cell death: methods and protocols / [ed] Marina Klemenčič; Simon Stael; Pitter F. Huesgen, Humana Press, 2022, , p. 8p. 13-20Chapter in book (Refereed)
Abstract [en]

Type II metacaspases (MCAs) are proteases, belonging to the C14B MEROPS family. Like the MCAs of type I and type III, they preferentially cleave their substrates after the positively charged amino acid residues (Arg or Lys) at the P1 position. Type II MCAs from various higher plants have already been successfully overexpressed in E. coli mostly as His-tagged proteins and were shown to be proteolytically active after the purification. Here we present a protocol for expression and purification of the only type II MCA from the model green alga Chlamydomonas reinhardtii. The two-step purification, which consists of immobilized metal affinity chromatography using cobalt as ion followed by size-exclusion chromatography, can be performed in 1 day and yields 4 mg CrMCA-II protein per liter of overexpression culture.

Place, publisher, year, edition, pages
Humana Press, 2022. p. 8
Series
Methods in Molecular Biology, ISSN 1064-3745, E-ISSN 1940-6029 ; 2447
Keywords
Cobalt IMAC, Metacaspase, Overexpression, Protease
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-196180 (URN)10.1007/978-1-0716-2079-3_2 (DOI)2-s2.0-85130766674 (Scopus ID)9781071620786 (ISBN)9781071620793 (ISBN)
Available from: 2022-06-14 Created: 2022-06-14 Last updated: 2022-06-27Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-7897-4038

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