| 1. |
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| 2. |
- Ferro, Lorenza, 1989-, et al.
(författare)
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DNA metabarcoding reveals microbial community dynamics in a microalgae-based municipal wastewater treatment open photobioreactor
- 2020
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Ingår i: Algal Research. - : Elsevier BV. - 2211-9264. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- Controlling the growth of desired algal strains in microalgal-based wastewater treatment systems is challenging, and understanding the dynamics and interactions in the system is vital for proper management. A pilot-scale open photobioreactor located in Northern Sweden, was inoculated with the culture collection strain Scenedesmus dimorphus UTEX 417, which had been grown in Nordic climate for 8 years. The microbial diversity of eukaryotic and prokaryotic communities and their seasonal dynamics were revealed throughout the growth period by high-throughput sequencing of 18S and 16S rRNA genes and correlated with various environmental factors. S. dimorphus was stable in batch culture, but other microalgae appeared during semi-batch mode and co-dominated the system as a consequence of predation by zooplankton. Desmodesmus, Pseudocharaciopsis, Chlorella, Characium and Oocystis were the main microalgal species co-occurring in the system, with Characium and Chlorella acting as main competitors to Scenedesmus. Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were the most abundant bacterial phyla, some of which showing significant positive or negative influence on Scenedesmus growth over time. Light, temperature, dissolved oxygen, pH and nutrients concentrations were found to have significant influence on the bacterial and/or zooplanktonic community changes.
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| 3. |
- Ferro, Lorenza, 1989-, et al.
(författare)
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Elucidating the symbiotic interactions between a locally isolated microalga Chlorella vulgaris and its co-occurring bacterium Rhizobium sp. in synthetic municipal wastewater
- 2019
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Ingår i: Journal of Applied Phycology. - : Springer. - 0921-8971 .- 1573-5176. ; 31:4, s. 2299-2310
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Tidskriftsartikel (refereegranskat)abstract
- Co-cultivation of microalgae and bacteria during municipal wastewater treatment can boost carbon and nutrient recovery as a result of their synergistic interactions. The symbiotic relationships between the locally isolated microalga Chlorella vulgaris and the bacterium Rhizobium sp., co-isolated from municipal wastewater, were investigated batchwise under photoautotrophic, heterotrophic, and mixotrophic conditions in a synthetic municipal wastewater medium. During photoautotrophic growth in BG11 medium, photosynthetic algal oxygenation and organic carbon production supported bacterial activity but no significant beneficial effects on microalgal growth were observed. In synthetic wastewater, a twofold higher biomass concentration was achieved in the axenic algal culture compared with the co-culture under heterotrophic conditions, suggesting a competition for nutrients. A comparable carbon removal was observed in all cultures (83–79% TOC), but a faster nitrogen consumption (59% TN) and complete phosphate assimilation (100% TP) was only achieved in the co-culture. A positive synergistic relationship was found under mixotrophic conditions, clearly supported by an in situ O2/CO2 exchange between the microorganisms. This mutualism led to a threefold higher biomass production with a 13-fold higher fatty acid content compared with the axenic algal culture, as well as a superior wastewater treatment performance (+ 58% TOC, + 41% TN and + 44% TP). The co-cultivation of C. vulgaris and Rhizobium is therefore suggested as a potential microbial consortium for a cost-efficient biomass generation during municipal wastewater reclamation, especially under mixotrophic conditions.
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| 4. |
- Ferro, Lorenza, 1989-, et al.
(författare)
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Growth performance and nutrient removal of a Chlorella vulgaris-Rhizobium sp. co-culture during mixotrophic feed-batch cultivation in synthetic wastewater
- 2019
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Ingår i: Algal Research. - : Elsevier. - 2211-9264. ; 44
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Tidskriftsartikel (refereegranskat)abstract
- The subarctic green algal strain Chlorella vulgaris 13-1, newly isolated from Northern Sweden, and its co-occurring bacterium Rhizobium sp. were tested for their ability to produce valuable biomass and remove nutrients from synthetic wastewater during mixotrophic feed-batch cultivation at multiple hydraulic retention times (HRTs = 7, 5 and 3 days). The algal-bacterial co-culture showed better performance compared to the corresponding axenic cultures (HRT = 7 days), with a biomass concentration of 0.63 +/- 0.03 g/L and removal rates of 49.5 +/- 6.1% TOC, 55.7 +/- 8.04% TN and 95.6 +/- 3.6% TP at steady-state. Culture stability and a high nutrient removal capacity were recorded in the algal-bacterial co-culture even at HRTs of 5 and 3 days. Interestingly, reducing the HRT from 7 to 5 days resulted in a higher lipid content of the biomass, further reduction of the HRT to 3 days enhanced both daily biomass productivity (1.03 g/L/day) and nutrient assimilation. Mixotrophic co-cultivation of C. vulgaris-Rhizobium sp. can successfully be applied for wastewater reclamation in continuous mode at HRT of 3-7 days, and thus is suitable for both summer and winter conditions in Nordic countries.
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| 5. |
- Ferro, Lorenza, 1989-, et al.
(författare)
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Statistical Methods for Rapid Quantification of Proteins, Lipids, and Carbohydrates in Nordic Microalgal Species Using ATR-FTIR Spectroscopy
- 2019
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Ingår i: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 24:18
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Tidskriftsartikel (refereegranskat)abstract
- Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy is a simple, cheap, and fast method to collect chemical compositional information from microalgae. However, (semi)quantitative evaluation of the collected data can be daunting. In this work, ATR-FTIR spectroscopy was used to monitor changes of protein, lipid, and carbohydrate content in seven green microalgae grown under nitrogen starvation. Three statistical methods-univariate linear regression analysis (ULRA), orthogonal partial least squares (OPLS), and multivariate curve resolution-alternating least squares (MCR-ALS)-were compared in their ability to model and predict the concentration of these compounds in the biomass. OPLS was found superior, since it i) included all three compounds simultaneously; ii) explained variations in the data very well; iii) had excellent prediction accuracy for proteins and lipids, and acceptable for carbohydrates; and iv) was able to discriminate samples based on cultivation stage and type of storage compounds accumulated in the cells. ULRA models worked well for the determination of proteins and lipids, but carbohydrates could only be estimated if already determined protein contents were used for scaling. Results obtained by MCR-ALS were similar to ULRA, however, this method is considerably easier to perform and interpret than the more abstract statistical/chemometric methods. FTIR-spectroscopy-based models allow high-throughput, cost-effective, and rapid estimation of biomass composition of green microalgae.
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| 6. |
- Ferro, Lorenza, 1989-
(författare)
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Wastewater treatment and biomass generation by Nordic microalgae : growth in subarctic climate and microbial interactions
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nordic native microalgal strains were isolated, genetically classified and tested for their ability to grow in municipal wastewater. Eight of the isolated strains could efficiently remove nitrogen and phosphate in less than two weeks. Two of these strains, Coelastrella sp. and Chlorella vulgaris, were found to have high biomass concentration and total lipid content; also two Desmodesmus sp. strains showed desirable traits for biofuel-feedstock, due to their fast growth rates and high oil content.The adaptation to subarctic climate was comparatively evaluated in three Nordic strains (C. vulgaris, Scenedesmus sp. and Desmodesmus sp.) and a collection strain (S. obliquus). Their growth performance, biomass composition and nutrients removal was investigated at standard (25°C) or low temperature (5°C), under continuous light at short photoperiod (3 h light, 25°C) or moderate winter conditions (6 h light, 15°C). Only the Nordic strains could grow and produce biomass at low temperature, and efficiently removed nitrogen and phosphate during both cold- and dark-stress. Phenotypic plasticity was observed in Scenedesmus and Desmodesmus under different growth conditions, adaptation to low temperature increased their carbohydrate content. Short photoperiod strongly reduced growth rates, biomass and storage compounds in all strains and induced flocculation in C. vulgaris, which, however, performed best under moderate winter conditions.The symbiotic relationships between the Nordic microalga C. vulgaris and the naturally co-occurring bacterium Rhizobium sp. were investigated batchwise under photoautotrophic, heterotrophic and mixotrophic conditions, comparing the co-culture to the axenic cultures. The photoautotrophic algal growth in BG11 medium mainly supported Rhizobium activity in the co-culture, with no significant effects on C. vulgaris. In synthetic wastewater, a synergistic interaction only occurred under mixotrophic conditions, supported by CO2/O2 exchange and a lower pH in the culture, resulting in higher biomass and fatty acids content and more efficient wastewater treatment in the co-culture. Under heterotrophic conditions, the lower biomass production in the co-culture suggested a competition for nutrients, although nutrients removal remained efficient.A pilot-scale high rate algal pond (HRAP) located in Northern Sweden was inoculated with the collection strain Scenedesmus dimorphus UTEX 417 and operated from spring to autumn. Using metabarcoding of 18S and 16S rRNA genes, the microbial diversity of eukaryotic and prokaryotic communities was revealed. S. dimorphus was initially stable in the culture, but other microalgal species later colonized the system, mainly due to parasitic infections and predation by zooplankton in summer. The main competitor algal species were Desmodesmus, Pseudocharaciopsis, Chlorella, Characium and Oocystis. Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were the most abundant bacterial phyla in the HRAP. The structure of the microbial communities followed a seasonal variation and partially correlated to environmental factors such as light, temperature and nutrients concentrations.Overall, these results contribute with new knowledge on the establishment and optimization of microalgal-based wastewater treatment systems coupled with biomass generation in Nordic areas. The use of native microalgal species is proposed as a potential strategy to overcome the limitations posed to algal cultivation in subarctic regions.
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| 7. |
- Gojkovic, Zivan, et al.
(författare)
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Modeling biomass production during progressive nitrogen starvation by North Swedish green microalgae
- 2020
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Ingår i: Algal Research. - : Elsevier. - 2211-9264. ; 47
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Tidskriftsartikel (refereegranskat)abstract
- Five newly isolated green algal species from Northern Sweden and one culture collection strain were tested for their ability to remove nitrogen and accumulate carbohydrates and neutral lipids (TAGs) under progressive nitrogen starvation. All six microalgal species increased biomass during N starvation, the amount of proteins decreased, and species dependent either TAGs and/or carbohydrates accumulated. Biomass of the algal strains Coelastrella sp. 3-4, Scenedesmus sp. B2-2 and S. obliquus RISE (UTEX 417) had very low final TAG content (≤3.4%) and high carbohydrate content (>41%) at the end of the starvation period. C. astroideum RW10 accumulated 9.2% TAGs and 53.9% carbohydrates during N-starvation; due to its modest growth rate (1.60 g/L and 1.06 1/day) resulting in low final biomass concentration, its cumulativeTAG and carbohydrate productivity were poor (175 mgTAG/system and 1.03 gCARBS/system). C. vulgaris 13-1 preferentially accumulated TAGs (10.3%) over carbohydrates (35%), with low minimal and maximal N quotas (2.27 and 11.6 mM/gDW) in its biomass and a very high growth rate (1.86 1/day) and cumulative TAGs productivity (278 mgTAG/system). Desmodesmus sp. RUC2 had the highest final biomass concentration (3.48 g/L) as well as cumulative TAG and carbohydrate productivity (269 mgTAG/system and 1.79 gCARBS/system). This species had the lowest minimal and maximal N quotas (1.58 and 8.50 mM/gDW) of all tested species, it can produce high amounts of biomass even when the available nitrogen concentration is low.A Droop's mathematical model with four basic parameters was applied to interpret the experimental data on N assimilation and biomass production under N starvation. The model corresponded well to the experimental data and therefore can successfully be applied to predict biomass production and N assimilation in Nordic algal species.
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| 8. |
- Lage, Sandra, et al.
(författare)
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Microalgae Cultivation for the Biotransformation of Birch Wood Hydrolysate and Dairy Effluent
- 2019
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Ingår i: Catalysts. - : MDPI. - 2073-4344. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate environmentally sustainable sources of organic carbon and nutrients, four Nordic green microalgal strains, Chlorella sorokiniana, Chlorella saccharophila, Chlorella vulgaris, and Coelastrella sp., were grown on a wood (Silver birch, Betula pendula) hydrolysate and dairy effluent mixture. The biomass and lipid production were analysed under mixotrophic, as well as two-stage mixotrophic/heterotrophic regimes. Of all of the species, Coelastrella sp. produced the most total lipids per dry weight (~40%) in the mixture of birch hydrolysate and dairy effluent without requiring nutrient (nitrogen, phosphorus, and potassium-NPK) supplementation. Overall, in the absence of NPK, the two-stage mixotrophic/heterotrophic cultivation enhanced the lipid concentration, but reduced the amount of biomass. Culturing microalgae in integrated waste streams under mixotrophic growth regimes is a promising approach for sustainable biofuel production, especially in regions with large seasonal variation in daylight, like northern Sweden. To the best of our knowledge, this is the first report of using a mixture of wood hydrolysate and dairy effluent for the growth and lipid production of microalgae in the literature.
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| 9. |
- Martínez, Juan Manuel, et al.
(författare)
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Use of pulsed electric field permeabilization to extract astaxanthin from the Nordic microalga Haematococcus pluvialis
- 2019
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Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 289
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Tidskriftsartikel (refereegranskat)abstract
- The Nordic microalgal strain Haematococcus pluvialis was exposed to various stress conditions to induce astaxanthin accumulation. Highest carotenoid content (19.1 mg·g−1dw) was achieved in nitrogen-free culture medium at a high light intensity. The efficiency of Pulsed Electric Field (PEF) pre-treatment of stressed fresh biomass of H. pluvialis followed by incubation in the growth medium was compared to classical disruption methods (bead-beating, freezing-thawing, thermal treatment or ultrasound) for the subsequent extraction of astaxanthin in ethanol. N-starved cells treated with PEF followed by aqueous incubation for 6 h resulted in extraction of 96% (18.3 mgcar·gdw−1) of the total carotenoid content compared to 80% (15.3 mgcar·gdw−1) using other physical methods. The proportion of free forms of astaxanthin was higher in PEF-treated samples compared to mechanical disruption, suggesting PEF triggering an esterase activity. PEF pre-treatment of the cells followed by incubation in growth medium improved astaxanthin extraction in the eco-friendly solvent ethanol.
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| 10. |
- Nzayisenga, Jean Claude, et al.
(författare)
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Screening Suitability of Northern Hemisphere Algal Strains for Heterotrophic Cultivation and Fatty Acid Methyl Ester Production
- 2020
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Ingår i: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 25:9
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Tidskriftsartikel (refereegranskat)abstract
- Rapid rises in atmospheric CO2 levels derived from fossil fuel combustion are imposing urgent needs for renewable substitutes. One environmentally friendly alternative is biodiesel produced from suitable microalgal fatty acids. Algal strains normally grow photoautotrophically, but this is problematic in Northern areas because of the light limitations for much of the year. Mixotrophic and particularly heterotrophic strains could be valuable, especially if they can be cultivated in municipal wastewater with contents of nutrients such as nitrogen and phosphorous that should be reduced before release into receiving water. Thus, the aim of this study was to screen for microalgal strains suitable for heterotrophic cultivation with a cheap carbon source (glycerol) for biodiesel production in Nordic, and other high-latitude, countries. One of the examined strains, a Desmodesmus sp. strain designated 2-6, accumulated biomass at similar rates in heterotrophic conditions with 40 mM glycerol as in autotrophic conditions. Furthermore, in heterotrophic conditions it produced more fatty acids, and ca. 50% more C18:1 fatty acids, as well as showing a significant decrease in C18:3 fatty acids, all of which are highly desirable features for biodiesel production.
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