Search Results (8)

The need to reduce anthropogenic greenhouse gas emissions drives the development of innovative carbon dioxide capture technologies. Microalgae-based biotechnologies represent a promising approach in this field. In this study, we evaluated the CO₂ assimilation efficiency of two novel microalgae strains, Desmodesmus armatus ARC-06 and Tribonema minus ARC-10, under low (0.04%) and high (1.5%) CO₂ conditions in a periodic cultivation system. The two strains exhibited distinct CO₂ adaptation strategies. D. armatus demonstrated higher tolerance to low CO₂ conditions, whereas T. minus showed superior performance under elevated CO₂. Although elevated CO₂ stimulated growth in both strains, their carbon dioxide sequestration efficiency (CDSE) differed markedly. The maximum CDSE was significantly higher in T. minus (30.0 ± 1.52%) compared to D. armatus (16.5 ± 1.12%). Similarly, the average CDSE over the cultivation period was greater in T. minus (19.1 ± 2.18%) than in D. armatus (11.8 ± 1.45%). These results underscore the importance of bioprospecting for novel microalgae strains, and the need for further research to develop efficient biological CO₂ sequestration methods. Full article

Microbial eukaryotes have essential roles in aquatic ecosystems, yet their diversity and ecological functions in extreme environments remain understudied compared to prokaryotes. This study aims to thoroughly characterize the composition and diversity of microbial eukaryotic communities in 14 geothermal waters across Croatia. Physicochemical analysis revealed significant variations in temperature (36–55 °C), pH (6.5–8.3), and nutrient concentrations, with all sites displaying anoxic conditions except for one. Sequencing of the V9 18S rRNA gene identified 134 taxa, predominantly from the Alveolata, Stramenopiles, and Opisthokonta supergroups. The highest diversity and richness were observed in aquifer groups with moderate temperatures and nutrient levels, while extreme sites exhibited reduced diversity. Among the key environmental factors shaping these communities, temperature, pH, and nitrate concentrations were most significant. Photoautotrophic and mixotrophic taxa, such as Ochrophyta, Dinoflagellata, and Chlorophyta, were prominent, reflecting their roles in primary production and nutrient cycling. Decomposers, including Basidiomycota and Ascomycota, were linked to organic matter degradation. Microeukaryotes showed adaptations to extreme conditions, such as thermotolerance and evolutionary shifts from phototrophy to heterotrophy, highlighting their ecological versatility. These findings underscore the potential of microbial eukaryotes in biotechnological applications, such as bioremediation and biofuel production. Genera like Tribonema and Navicula demonstrated promising capabilities in nutrient removal and CO₂ fixation. However, further research is necessary to investigate and confirm their suitability for these purposes. To summarize, our research provides new insights into understudied microbial eukaryotes in Croatian hot springs that represent a valuable model for exploring microbial diversity, ecological interactions, and industrial applications in extreme environments. Full article

The aim of this study is to investigate the differences in the accumulation capacity of chrysolaminarin among six Tribonema species and to isolate this polysaccharide for immunomodulatory activity evaluation. The results showed that T. aequale was the most productive strain with the highest content and productivity of chrysolaminarin, which were 17.20% (% of dry weight) and 50.91 mg/L/d, respectively. Chrysolaminarin was then extracted and isolated from this alga, and its monosaccharide composition was mainly composed of a glucose (61.39%), linked by β-D-(1→3) (main chain) and β-D-(1→6) (branch chain) glycosidic bonds, with a molecular weight of less than 6 kDa. In vitro immunomodulatory assays showed that it could activate RAW264.7 cells at a certain concentration (1000 μg/mL), as evidenced by the increased phagocytic activity and upregulated mRNA expression levels of IL-1β, IL6, TNF-α and Nos2. Moreover, Western blot revealed that this polysaccharide stimulated the phosphorylation of p-65, p-38 and JNK in NF-κB and MAPK signaling pathways. Overall, these findings provide a reference for the further development and utilization of algae-based chrysolaminarin, while also offering an in-depth understanding of the immunoregulatory mechanism. Full article

Dissolved organic matter (DOM) is an important component of aquatic environments; it plays a key role in the biogeochemical cycles of many chemical elements. Using excitation–emission matrix fluorescence spectroscopy, we examined the fluorescent fraction of DOM (FDOM) produced at the stationary phase of growth of five strains of microalgae sampled and isolated from the Ob and Yenisei gulfs. Based on the morphological and molecular descriptions, the strains were identified as diatoms (Asterionella formosa, Fragilaria cf. crotonensis, and Stephanodiscus hantzschii), green microalgae (Desmodesmus armatus), and yellow-green microalgae (Tribonema cf. minus). Three fluorescent components were validated in parallel factor analysis (PARAFAC): one of them was characterized by protein-like fluorescence (similar to peak T), two others, by humic-like fluorescence (peaks A and C). The portion of fluorescence intensity of humic compounds (peak A) to the total fluorescence intensity was the lowest (27 ± 5%) and showed little variation between species. Protein-like fluorescence was most intense (45 ± 16%), but along with humic-like fluorescence with emission maximum at 470 nm (28 ± 14%), varied considerably for different algae strains. The direct optical investigation of FDOM produced during the cultivation of the studied algae strains confirms the possibility of autochthonous production of humic-like FDOM in the Arctic shelf regions. Full article

It has long been explored to use EPA-rich unicellular microalgae as a fish oil alternative for production of the high-value omega-3 fatty acid eicosapentaenoic acid (EPA, 20:5, n-3). However, none of the efforts have ever reached commercial success. This study reported a filamentous yellow-green microalga Tribonema aequale that possesses the ability to grow rapidly and synthesize significant amounts of EPA. A series of studies were conducted in a glass column photobioreactor under laboratory culture conditions and in pilot-scale open raceway ponds outdoors. The emphasis was placed on the specific nutrient requirements and the key operational parameters in raceway ponds such as culture depth and mixing regimes. When optimized, T. aequale cells contained 2.9% of EPA (w/w) and reached a very high biomass concentration of 9.8 g L⁻¹ in the glass column photobioreactor. The cellular EPA content was increased further to 3.5% and the areal biomass and EPA productivities of 16.2 g m⁻² d⁻¹ and 542.5 mg m⁻² d⁻¹, respectively, were obtained from the outdoor pilot-scale open raceway ponds, which were the record high figures reported thus far from microalgae-based EPA production. It was also observed that T. aequale was highly resistant to microbial contamination and easy for harvesting and dewatering, which provide two additional competitive advantages of this filamentous microalga over the unicellular counterparts for potential commercial production of EPA and other derived co-products. Full article

Eukaryotic filamentous yellow-green algae from the Tribonema genus are considered to be excellent candidates for biofuels and value-added products, owing to their ability to grow under autotrophic, mixotrophic, and heterotrophic conditions and synthesize large amounts of fatty acids, especially unsaturated fatty acids. To elucidate the molecular mechanism of fatty acids and/or establish the organism as a model strain, the development of genetic methods is important. Towards this goal, here, we constructed a genetic transformation method to introduce exogenous genes for the first time into the eukaryotic filamentous alga Tribonema minus via particle bombardment. In this study, we constructed pSimple-tub-eGFP and pEASY-tub-nptⅡ plasmids in which the green fluorescence protein (eGFP) gene and the neomycin phosphotransferase Ⅱ-encoding G418-resistant gene (nptⅡ) were flanked by the T. minus-derived tubulin gene (tub) promoter and terminator, respectively. The two plasmids were introduced into T. minus cells through particle-gun bombardment under various test conditions. By combining agar and liquid selecting methods to exclude the pseudotransformants under long-term antibiotic treatment, plasmids pSimple-tub-eGFP and pEASY-tub- nptⅡ were successfully transformed into the genome of T. minus, which was verified using green fluorescence detection and the polymerase chain reaction, respectively. These results suggest new possibilities for efficient genetic engineering of T. minus for future genetic improvement. Full article

Palmitoleic acid, one scarce omega-7 monounsaturated fatty acid, has important applications in the fields of medicine and health products. Tribonema has been considered as a promising candidate for the production of palmitoleic acid due to its high lipid and palmitoleic acid content and remarkable heterotrophic ability. The high-density heterotrophic cultivation of Tribonema minus was conducted in this work, and the highest biomass of 42.9 g L⁻¹ and a relatively low lipid content of 28.7% were observed. To further enhance the lipid and palmitoleic acid accumulation, induction strategies under two regimes of phototrophy and heterotrophy with different conditions were investigated and compared. Results demonstrated encouraging promotions both by heterotrophic and phototrophic ways, and the final lipid contents reached 41.9% and 49.0%, respectively. In consideration of the time cost, however, the induction under heterotrophic conditions was much more advantageous, by which the highest lipid and palmitoleic acid productivities of 1.77 g L⁻¹ d⁻¹ and 924 mg L⁻¹ d⁻¹ were obtained respectively, with the lipid yield on glucose of 0.26 g g⁻¹. Full article

Recently, Tribonema sp., a kind of filamentous microalgae, has been studied for biofuel production due to its accumulation of triacylglycerols. However, the polysaccharides of Tribonema sp. and their biological activities have rarely been reported. In this paper, we extracted sulfated polysaccharides from Tribonema sp. (TSP), characterized their chemical composition and structure, and determined their immunostimulation and anticancer activities on RAW264.7 macrophage cells and HepG2 cells. The results showed that TSP is a sulfated polysaccharide with a M_w of 197 kDa. TSP is a heteropolysaccharide that is composed mainly of galactose. It showed significant immune-modulatory activity by stimulating macrophage cells, such as upregulating interleukin 6 (IL-6), interleukin 10 (IL-10), and tumor necrosis factor α (TNF-α). In addition, TSP also showed significant dose-dependent anticancer activity (with an inhibition rate of up to 66.8% at 250 µg/mL) on HepG2 cells as determined by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The cycle analysis indicated that the anticancer activity of TSP is mainly the result of induced cell apoptosis rather than affecting the cell cycle and mitosis of HepG2 cells. These findings suggest that TSP might have potential as an anticancer resource, but further research is needed, especially in vivo experiments, to explore the anticancer mechanism of TSP. Full article