Immobilization of a Mixed Culture of Oxygenic Phototrophic Microorganisms on a Chitosan-Based Sorbent for Nutrient Bioremoval

Applied Biochemistry and Microbiology - The immobilization of cells of a mixed culture of the microalgae (MA) Micractinium sp. NAMSU A-19 and cyanobacteria (CB) Synechococcus sp. 1Dp66E-1 on a...     

Stress-induced changes in pigment and fatty acid content in the microalga Desmodesmus sp. Isolated from a White Sea hydroid

Effects of light intensity, nitrogen availability, and inoculum density on growth and the content of esterified fatty acids (FA), chlorophylls, and carotenoids in Desmodesmus sp. 3Dp86E-1 chlorophyte alga isolated from the White Sea hydroid Dynamena pumila L. were investigated. The growth of algae in the complete BG-11 medium was not limited by irradiances up to 480 μE/(m² s) PAR but depended on the inoculum density. Under nitrogen starvation conditions, high-intensity light retarded growth of the microalga; this effect was less pronounced in the cultures initiated at high inoculum densities. The highest FA percentage in biomass (30% at the 3rd day of cultivation) was detected in nitrogen-starving cultures grown under high light conditions; however, the highest volumetric FA content (0.25 g/L) was attained on a complete medium at 480 μE/(m² s). An increase in the content of oleic acid (18:1) on the background of a decrease in linolenic acid (18:3) was characteristic of the microalga under stress conditions. The microalga was found to be non-carotenogenic. Nitrogen starvation brought about a dramatic decrease in chlorophyll content on the background of relatively constant carotenoid content. On nitrogen-deplete medium, the high light did not trigger the adaptive response of the pigment apparatus. The changes in absorption spectra of Desmodesmus sp. 3Dp86E-1 cell suspensions reflected the increase in relative contribution of carotenoids to light absorption by the microalgal cells; these changes were tightly related with FA accumulation. The mechanisms of acclimation of Desmodesmus sp. 3Dp86E-1 to high light and nitrogen starvation are discussed in view of possible biotechnological applications of this alga.     

Hints for understanding microalgal phosphate-resilience from Micractinium simplicissimum IPPAS C-2056 (Trebouxiophyceae) isolated from a phosphorus-polluted site

Journal of Applied Phycology - A novel chlorophyte algae strain with outstanding resilience to high inorganic phosphate (Pi) concentrations in the medium was isolated from a...     

Cationic penetrating antioxidants switch off Mn cluster of photosystem II in situ

Photosynthesis Research - Photosystem I (PSI) generates the most negative redox potential found in nature, and the performance of solar energy conversion into alternative energy sources in...     

Desmodesmus sp. 3Dp86E-1—a Novel Symbiotic Chlorophyte Capable of Growth on Pure CO2

A novel chlorophyte Desmodesmus sp. 3Dp86E-1 isolated from a White Sea hydroid Dynamena pumila was cultivated at CO₂ levels from atmospheric (the ‘low-CO₂’ conditions) to pure carbon dioxide (the 5, 20, and 100 % CO₂ conditions) under high (480 μE/(m² s) PAR) light. After 7 days of cultivation, the ‘100 % CO₂’ (but not 5 or 20 % CO₂) cells possessed ca. four times higher chlorophyll content per dry weight (DW) unit than the low-CO₂ culture. The rate of CO₂ fixation under 100 % CO₂ comprised ca. 1.5 L/day per L culture volume. After a lag period which depended on the CO₂ level, biomass accumulation and volumetric fatty acid (FA) content of the Desmodesmus sp. 3Dp86E-1 bubbled with CO₂-enriched gas mixtures increased and was comparable to that of the culture continuously bubbled with air. Under the low-to-moderate CO₂ conditions, the FA percentage of the algal cells increased (to 40 % DW) whereas under high-CO₂ conditions, FA percentage did not exceed 15 % DW. A strong increase in oleate (18:1) proportion of total FA at the expense of linolenate (18:3) was recorded in the ‘100 % CO₂’ cells. Electron microscopy and pulse–amplitude-modulated chlorophyll fluorescence investigation revealed no damage to or significant downregulation of the photosynthetic apparatus in ‘100 % CO₂’ cells grown at the high-PAR irradiance. Possible mechanisms of high-CO₂ tolerance of Desmodesmus sp. 3Dp86E-1 are discussed in view of its symbiotic origin and possible application for CO₂ biomitigation.     

Amyloidogenic peptides of yeast cell wall glucantransferase Bgl2p as a model for the investigation of its pH-dependent fibril formation

The pH-dependence of the ability of Bgl2p to form fibrils was studied using synthetic peptides with potential amyloidogenic determinants (PADs) predicted in the Bgl2p sequence. Three PADs, FTIFVGV, SWNVLVA and NAFS, were selected on the basis of combination of computational algorithms. Peptides AEGFTIFVGV, VDSWNVLVAG and VMANAFSYWQ, containing these PADs, were synthesized. It was demonstrated that these peptides had an ability to fibrillate at pH values from 3.2 to 5.0. The PAD-containing peptides, except for VDSWNVLVAG, could fibrillate also at pH values from pH 5.0 to 7.6. We supposed that the ability of Bgl2p to form fibrils most likely depended on the coordination of fibrillation activity of the PAD-containing areas and Bgl2p could fibrillate at mild acid and neutral pH values and lose the ability to fibrillate with the increasing of pH values. It was demonstrated that Bgl2p was able to fibrillate at pH value 5.0, to form fibrils of various morphology at neutral pH values and lost the fibrillation ability at pH value 7.6. The results obtained allowed us to suggest a new simple approach for the isolation of Bgl2p from Saccharomyces cerevisiae cell wall.     

Amyloid-like properties of Saccharomyces cerevisiae cell wall glucantransferase Bgl2p: Prediction and experimental evidences

Glucantransferase Bgl2p is a major conserved cell wall constituent described for a wide range of yeast species. In the baker''s yeast Saccharomyces cerevisiae it is the only non-covalently bound cell wall protein that cannot be released from cell walls by sequential SDS and trypsin treatment. It contains seven amyloidogenic determinants. Circular dichroism analysis and fluorescence spectroscopy with thioflavin T indicate the presence of β-sheet structures in Bgl2p isolates. Bgl2p forms fibrils, a process that is enforced in the presence of other cell wall components. Thus the data obtained is the first evidence for amyloid-like properties of yeast cell wall protein—glucantransferase Bgl2p.Key words: glucantransferase Bgl2p, cell wall amyloid-like protein     

Screening of the culture media with different concentrations of nutrients for cultivation of the microalgae associated with the invertebrates of the White Sea

The growth and biomass accumulation of three microalgal strains of Desmodesmus (Scenedesmaceae, Chlorophyceae), 1Рm66В, 2Cl66E, and 3Dp86Е-1, isolated from the White Sea benthic invertebrates were studied under conditions of batch culture in different standard media (BG-11, Prat, Goldberg, Gromov, Tamiya, artificial seawater) and modified media. The culture condition, biomass accumulation, and uptake of nitrate and phosphate were recorded. A significant alkalization of the culture medium up to pH 10 has been observed during a vigorous growth of the microalgae. The most significant biomass accumulation has been recorded in BG-11 (in complete or modified medium with addition of artificial seawater), Tamiya, and Prat media. Addition of seawater did not affect the growth of Desmodesmus sp. in the nitrate-containing media, although that maintained growth of the microalgae in the nitrogen-lacking media without cell aggregation. The BG-11 medium appears suitable for isolation and cultivation of both symbiotic and free-living microalgae by all the tested features. The Prat medium is the best for maintaining the microalgal strains in living collection.     

A new subarctic strain of <Emphasis Type="Italic">Tetradesmus obliquus</Emphasis>—part I: identification and fatty acid profiling

We isolated a new subarctic strain Tetradesmus obliquus IPPAS S-2023 (Scenedesmaceae, Chlorophyceae) from rock baths in the White Sea. To verify its taxonomic assignment, internal transcribed spacer 2 (ITS2) of the strain was sequenced and its secondary structure was compared with predicted ITS2 secondary structures of Scenedesmaceae. The analysis of the ITS2 made it possible to assign the new strain IPPAS S-2023 to the species T. obliquus. The ultrastructural studies and energy-dispersive X-ray spectroscopy (EDX) analysis revealed a marked accumulation of vacuolar inclusions enriched in phosphorus and nitrogen (N) as well as cytoplasmiс oil bodies. Most of predicted properties of biodiesel derived from the fatty acids profile of the strain grown in the N-free medium complied with the requirements of European and American standards. The results suggest that the new subarctic strain T. obliquus IPPAS S-2023 is a promising candidate for nutrients biosequestration and for biodiesel production. In a companion paper, we assess its biomass production capability and suitability and demonstrated suitability of IPPAS S-2023 as a reference strain for studies on elevated CO₂ stress effects selection of carbon dioxide-tolerant microalgae by comparison with a CO₂-tolerant strain IPPAS S-2014.