Microalga Dunaliella Research Articles

Rainbow trout farm effluent as a potential source of feed and medium for mass culture of Artemia parthenogenetica

This study was conducted to evaluate the effects of the trout farm effluent (TFE) co-feeding with microalgae Dunaliella tertiolecta (MA) on Artemia parthenogenetica biomass production. The feeding regimes were 95% TFE+5% MA, 85% TFE+15% MA, and 75% TFE+25% MA, with different Artemia densities of 250, 500, 1000 and 1500 individuals L−1 in 1-L tanks and 1000 individuals L−1 in 800-L tanks in three replicates in two distinct experiments, comprising 48 experimental units in 1-L tank stage (including four controls fed 0%TFE+100% MA in four densities) and 9 experimental units in 800-L stage. The growth performance and nutritional value of animals were measured on days 8, 11, 14, 17, 20 and 23. The highest growth and survival performance was observed in the treatment containing 75% TFE+25% MA at a density of 250 individuals L−1 (1-L tanks) and 85% TFE+15% MA at a density of 1000 individuals L−1 (800-L tanks). Furthermore, higher protein, carbohydrate, and lipid contents were obtained in the treatment feed 75% TFE+25% MA for both 1-L and 800-L tanks. In the same treatment, significantly higher contents of fatty acids were obtained too. However, the maximum amount for each fatty acids was different based on the different densities. Based on the present result, Artemia parthenogenetica can be cultured successfully using trout farm effluent even with high substitution ratio instead of microalgae as the main feed for Artemia biomass production.

Toxic effects of Fe2WO6 nanoparticles towards microalga Dunaliella salina: Sonochemical synthesis nanoparticles and investigate its impact on the growth

In this work, Fe2WO6 nanoparticles were synthesized by the ultrasound-assisted precipitation method. Various conditions were applied, including the change of the pH factor and reaction time for the synthesis of nanoparticles. After confirming the synthesis of the nanoparticles by various analyzes and evaluating their size and morphology, one of the conditions for the synthesis of the nanoparticles were selected as the optimum condition. The samples were added to the growth medium of a well-known microalga, Dunaliella salina at three concentrations of 20, 40 and 80 ppm to evaluate the effect of nanoparticles on biological systems. After 10 days different biological parameters were measured and compared with those of the control sample. According to the results, at concentration of 20 ppm the number of cells, the amount of chlorophyll a, and b, and biomass increased compared to the control samples. The Carotenoid level was higher in the treatment with 40 ppm of nanoparticles than that in the control samples. Compared to the control sample, the level of lipid peroxidation and the ratio of carbohydrate to amide II showed to be higher under 80 ppm treatment of particles. According to HCA analysis, both the evaluated parameters and concentrations of nanoparticles were divided into two general categories. Overall results showed that the effect of Fe2WO6 nanoparticles on microalgae could be a dose-dependent phenomenon, so that the addition of 20 ppm nanoparticles in the culture media helped the growth and the physiological status of algae. On the other hand, the application of a higher concentration of nanoparticles negatively affects algal biology. The results showed that the algae could be successfully used to precise screen of various nanoparticles in terms of safety especially in aquatic environments and also biotechnological applications.

Dietary Supplementation with Dunaliella Tertiolecta Prevents Whitening of Brown Fat and Controls Diet-Induced Obesity at Thermoneutrality in Mice.

We investigated the effect of evodiamine-containing microalga Dunaliella tertiolecta (DT) on the prevention of diet-induced obesity in a thermoneutral C57BL/6J male (30 °C). It attenuates the activity of brown adipose tissue (BAT), which accelerates diet-induced obesity. Nine-week-old mice were fed a high-fat diet supplemented with 10 g (Low group) or 25 g (High group) DT powder per kg food for 12 weeks. Compared to control mice without DT supplementation, body weight gain was significantly reduced in the High group with no difference in food intake. Tissue analyses indicated maintenance of multilocular morphology in BAT and reduced fat deposition in liver in DT-supplemented mice. Molecular analysis showed a significant decrease in mammalian target of rapamycin−ribosomal S6 protein kinase signaling pathway in white adipose tissue and upregulation in mRNA expression of brown fat-associated genes including fibroblast growth factor-21 (Fgf21) and uncoupling protein 1 (Ucp1) in BAT in the High group compared to the control. In the experiments using C3H10T1/2 adipocytes, DT extract upregulated mRNA expression of brown fat-associated genes in dose-dependent and time-dependent manners, accompanied by a significant increase in secreted FGF21 levels. Our data show the ability of DT as a nutraceutical to prevent brown fat attenuation and diet-induced obesity in vivo.

Toxicity of Different Zinc Oxide Nanomaterials at 3 Trophic Levels: Implications for Development of Low-Toxicity Antifouling Agents.

Because zinc oxide (ZnO) nanomaterials are used in antifouling and antibacterial solutions, understanding their toxic effects on different aquatic organisms is essential. In the present study, we evaluated the toxicity of ZnO nanoparticles of 10 to 30 nm (ZnONPI) and 80 to 200 nm (ZnONPII), ZnO nanorods (width 80 nm, height 1.7 µm) attached to the support substrate (glass, ZnONRG) and not attached (ZnONRS), as well as Zn2+ ions at concentrations ranging from 0.5 to 100 mg/L. Toxicity was evaluated using the microalga Dunaliella salina, the brine shrimp Artemia salina, and the marine bacterium Bacillus cereus. The highest toxicity was observed for ZnONPs (median lethal concentration [LC50] ~15 mg/L) and Zn2+ ions (LC50 ~13 mg/L), whereas the lowest toxicity found for ZnO nanorods (ZnONRG LC50 ~60 mg/L; ZnONRS LC50 ~42 mg/L). The presence of the support substrate in case of ZnO nanorods reduced the associated toxicity to aquatic organisms. Smaller ZnONPs resulted in the highest Zn2+ ion dissolution among tested nanostructures. Different aquatic organisms responded differently to ZnO nanomaterials, with D. salina and B. cereus being more sensitive than A. salina. Toxicity of nanostructures increased with an increase of the dose and the time of exposure. Supported ZnO nanorods can be used as a low-toxicity alternative for future antimicrobial and antifouling applications. Environ Toxicol Chem 2020;39:1343-1354. © 2020 SETAC.

Identification of microRNAs response to high light and salinity that involved in beta-carotene accumulation in microalga Dunaliella salina

MicroRNAs (miRNAs) are a class of endogenous non-coding RNAs that play a crucial role in post-transcriptional gene regulation not only in animals and land plants, but also in microalgae. Among all the microalga, Dunaliella salina (D. salina) has the highest content of beta-carotene, and a draft genome of this species was recently published. Thus far, few D. salina miRNAs have been identified. In this study, deep sequencing was performed to identify miRNAs in wild-type D. salina (Control) and in a high light and high salinity treatment group (HLS). Three small RNA (sRNA) libraries were constructed for Control and HLS, and an average of 11,542,169 and 16,877,598 clean tags were obtained, respectively. The sRNA length distribution showed that 21 nt sRNAs were the most abundant class in both Control and HLS, which is consistent with the sRNA distribution of model organism Chlamydomonas reinhardtii. Eighty-four known miRNAs and 1054 novel miRNAs were found in Control. Among them, nine known miRNAs and 39 novel miRNAs had altered levels in response to HLS treatment. The expression differences of selected miRNAs and their target genes in Control and HLS were verified by qRT-PCR, which showed that novel-m0533-3p was up-regulated and its predicted target malate dehydrogenase encoded gene was clearly down-regulated in HLS at both transcription and the protein level. Moreover, some key carotenoid pathway genes, such as PSY, PDS and LCYB were all up-regulated in HLS. These findings are providing a new insights into a miRNA-mediated beta-carotene accumulation mechanism in D. salina.

High salinity acclimatization alleviated cadmium toxicity in Dunaliella salina: Transcriptomic and physiological evidence

In the present study, we tested the hypothesis that high salinity acclimatization can mitigate cadmium (Cd) toxicity in the microalga Dunaliella salina. To this end, microalgal cells were subjected to high salinity (60 g/L) for 12 weeks until the growth rate remained stable between generations and were then exposed to 2.5 mg/L of Cd for 4 days. Acute Cd toxicity impaired cell growth by increasing Cd bioaccumulation and lipid peroxidation, which reduced cellular pigment, total protein, and glutathione content. It also significantly weakened photosynthetic efficiency and total antioxidant capacity. However, acclimatization to high salinity alleviated these negative effects under Cd stress. To understand the potential mechanisms behind this phenomenon, 12 cDNA libraries from control, Cd-exposed (Cd), high salinity-acclimated (Salinity), and high salinity-acclimated with Cd exposure (Salinity + Cd) cells were derived using RNA sequencing. A total of 2019, 1799, 2150 and 1256 differentially expressed genes (DEGs) were identified from sample groups Salinity / Control, Cd / Control, Salinity + Cd / Control, and Salinity + Cd / Cd, respectively. Some of these DEGs were significantly enriched in ribosome, photosynthesis, stress defense, and photosynthesis-antenna proteins. Among these genes, 82 ribosomal genes were up-regulated in Salinity / Control (corrected P = 3.8 × 10−28), while 81 were down-regulated in Cd / Control (corrected P = 1.1 × 10-24). Moreover, high salinity acclimatization up-regulated 8 photosynthesis genes and 18 stress defense genes compared with the control. Additionally, 3 photosynthesis genes, 11 stress defense genes and 11 genes encoding light harvesting proteins were up-regulated by high salinity acclimatization under Cd exposure. Overall, high salinity acclimatization mitigated Cd toxicity, possibly by up-regulating the transcription of photosynthesis, stress defense, and ribosomal genes. These results provide new insights on cross-tolerance in microalgae.

Stereoisomers of Colourless Carotenoids from the Marine Microalga Dunaliella salina.

Carotenoids comprise a diverse range of naturally occurring stereoisomers, which differ in their physico-chemical properties. Their biosynthesis begins with phytoene, which is a rarity among carotenoids because it is colourless. Phytoene is sought after as a skin protectant against harmful UV range B (290–320 nm) and C (100–290 nm) light, and as a natural skin-whitening agent and is synthesized from geranylgeranyl diphosphate. Geranylgeranyl diphosphate is catalysed by phytoene synthase and phytoene desaturase to phytoene and phytofluene, respectively. The subsequent steps involve desaturation, isomerisation and cyclisation reactions to form α- and β-carotene stereoisomers, via all-trans lycopene. The marine microalga Dunaliella salina is the richest source of β-carotene, but it can accumulate phytoene and phytofluene as well. In the present study, different analytical tools including High-Performance Liquid Chromatography (HPLC), Ultra-Performance Convergence Chromatography (UPC2-MS) and Nuclear Magnetic Resonance (NMR) were used to characterize and quantify the phytoene isomeric configurations in D. salina in order to explore both the feasibility of D. salina as a cell factory for phytoene production and to gain new insight into the carotenoid synthesis pathway in D. salina. D. salina, similar to tomato, produced predominantly 15-cis phytoene isomer (>98%) and a trace amount of all-trans phytoene (<2%). High light stress, red light stress, or use of a phytoene desaturase inhibitor or a mitotic disrupter herbicide led to the accumulation of 15-cis phytoene but not all-trans phytoene. 9-cis phytoene was not detected in any of the extracts of D. salina biomass. Our main findings suggest that 15-cis phytoene is the most abundant isomer in D. salina and that it is subject to a series of isomerisation and desaturation reactions to form all-trans and 9-cis β-carotene.

Scale-up of Dunaliella salina cultivation: from strain selection to open ponds

The microalga Dunaliella salina was studied at the main stages of transition from laboratory to pilot-scale cultivation: strain selection, nutrient medium selection, estimation of influence of physicochemical factors on accumulation of carotenoids and evaluation of the selected strain growing technology at pilot conditions. Dunaliella salina strain IBSS-2 was recognized as promising for commercial cultivation due to the combination of high-production characteristics, environmental stress resistance, and relative easiness of transition to the carotenogenesis stage. The influence of stress factors on the D. salina culture productivity in two nutrient media was estimated. It was shown that light effect combined with nutrients deficiency is the key factor for β-carotene accumulation. The influence of increased irradiance caused the increase of carotenoid content in D. salina cells up to 8%, and increasing irradiance and salinity resulted in carotenoid productivity going up 1.5 times. Testing of D. salina pilot cultivation system demonstrated that productivity at the first cultivation stage was about 6 g m−2 day−1 in both batch and semicontinuous mode. During pilot D. salina cultivation in Crimea, the culture transition to the carotenogenesis stage was achieved both in summer and autumn. The concentration of carotenoids in the ponds was 200 and 600 mg m−2 with a carotenoid/chlorophyll a (Car/Chl a) ratio of 7 and 4.5 in summer and autumn, respectively. The possibility to use natural population of D. salina cells from salterns as inoculum and brine as a nutrient medium base was demonstrated. The study results suggest that the proposed approach can be recommended for D. salina commercial cultivation.

Accumulation of 13C-labelled phenanthrene in phytoplankton and transfer to corals resolved using cavity ring-down spectroscopy.

Polycyclic aromatic hydrocarbons (PAHs) are widespread pollutants in marine ecosystems including threatened and potentially sensitive coral reefs. Lower organisms such as phytoplankton, known to bioconcentrate PAHs, could serve as potential entry points for these chemicals into higher trophic levels. Here, we present a novel method using a 13C-labelled PAH and cavity ring-down spectroscopy (CRDS) to investigate accumulation, uptake rates and trophic transfer of PAHs in corals, which are key organisms to sustain biodiversity in tropical seas. We quantified the accumulation of 13C-phenanthrene in the marine microalga Dunaliella salina, and in the coral Acropora millepora after diffusive uptake from seawater or dietary uptake via labelled D. salina. Additionally, we monitored the photophysiological health of D. salina and A. millepora during phenanthrene exposure by pulse-amplitude modulation (PAM) fluorometry. Dose-dependent accumulation of 13C-phenanthrene in the microalga showed a mean bioconcentration factor (BCF) of 2590±787Lkg-1 dry weight. Corals accumulated phenanthrene from both exposure routes. While uptake of 13C-phenanthrene in corals was faster through aqueous exposure than dietary exposure, passive diffusion showed larger variability between individuals and both routes resulted in accumulation of similar concentrations of phenanthrene. The 13C-PAH labelling and analysis by CRDS proved to be a highly sensitive method. The use of stable isotopic label eliminated additional toxicity and risks by radioactive isotopic-labelling, and CRDS reduced the analytical complexity of PAH (less biomass, no extraction, fast analysis). The simultaneous, precise quantification of both carbon content and 13C/12C ratio (δ13C) enabled accurate determination of 13C-phenanthrene accumulation and uptake rate. This is the first study to provide empirical evidence for accumulation of phenanthrene in a phytoplankton-coral food chain.

The use of 18S ribosomal DNA, ITS and rbcL molecular markers to study the genus Dunaliella (Dunaliellaceae) in Iranian samples: A phylogenetic approach

Abstract The microalga Dunaliella has been the focus of attention over recent decades owing to its high biotechnological potential for the production of β-carotene, biofuels and even as a good expression system for the production of recombinant proteins. Different species of this genus have unique features, biological characteristics and biotechnological potential. Therefore, it is necessary to have a clear and reliable taxonomic method to identify different species of Dunaliella. Although several taxonomic systems are available for Dunaliella based on morphological, physiological and molecular features, none of these methods are reliable enough and some controversies exist over different classification systems. In the current study, molecular techniques and bioinformatics tools have been used to re-assess the phylogenetic position of Dunaliella species based on 18S ribosomal DNA (18S rDNA), ITS and rbcL regions. The overall findings based on these markers provide a new and more reliable tool for phylogenetic analysis of Dunaliella species/strains.

Deciphering the Biological Activities of Dunaliella sp. Aqueous Extract from Stressed Conditions on Breast Cancer: from in Vitro to in Vivo Investigations.

In order to harness local resources to improve well-being and human health, we aim in this study to investigate if the microalgae Dunaliella sp. isolated from the Tunisian coastal zone possesses any anticancer activity. Dunaliella sp. was cultured under normal (DSC) or stressed (DSS) conditions and extracted using different procedures. The biological activity assessment was performed on the Triple Negative Breast Cancer (TNBC) using 4T1 murine cells as a model. Results indicate that: (i) aqueous extract was the most cytotoxic compared to ethanolic and hydroalcoholic extracts; (ii) DSS activity was superior to that of DSC. DSS extracts induced apoptosis rather than necrosis, as evidenced by DNA fragmentation, PARP-1 cleavage and caspase-3 activation. Evaluation in an orthotopic TNBC model validated the anticancer activity in vivo. Intratumoral injection of DSS extract resulted in reduced tumor growth and an enhanced immune system activation. On the transcriptional side, the expression level of the immunosuppressive enzyme Arg-1 was decreased, as well as those of NOS-2 and COX-2 genes. These results suggest a potential anticancer activity of Tunisian Dunaliella sp. deserving further attention.

Assessment, monitoring and modelling of the abundance of Dunaliella salina Teod in the Meighan wetland, Iran using decision tree model.

The microalga Dunaliella salina has been broadly studied for different purposes such as beta-carotene production, toxicity assessment and salinity tolerance, yet research on the habitat suitability of this alga has rarely been reported. The present research aims to apply a suitable monitoring and modelling methods (two critical steps in ecological researches) to predict the abundance of D. salina. The abundance of D. salina was predicted by decision tree model (J48 algorithm) in 10 different monitoring sites during 1-year study period (2016-2017) in the Meighan wetland, one of the valuable hypersaline wetlands in Iran. The abundance of alga (as output of model) together with various water quality and physical-habitat wetland characteristics (as inputs of model) were monthly and repeatedly monitored in two different depths (one from the surface layer and another one from the depth of maximum 50cm) which in total resulted in 240 instances (120 instances for each depth). Based on trial and error, a sevenfold cross-validation resulted in the highest predictive performances of the model (CCI > 75% and Cohen's Kappa > 0.65). According to the model's prediction, the number of sunny hours might be one of the most important driving parameters to meet the habitat requirements of alga in the hypersaline wetland. Model also predicted that an increase in dissolved oxygen and sodium concentrations might increase the abundance of D. salina in the salt wetland. In contrast, an increase in total suspended solids concentration and monthly precipitation might lead to a decrease in the abundance of alga. Chi-square test of independence showed a significant difference between the abundance of the D. salina and spatio-temporal patterns in the wetland (Pearson chi-square statistic = 221.7, p= 0.001) so warm seasons (spring and summer) had more contribution to the sampling of the species than cold seasons (autumn and winter). The difference in the abundance of the species in different sampling sites can be attributed due to the various anthropogenic activities.

Reconstruction and analysis of a carbon-core metabolic network for Dunaliella salina

BackgroundThe green microalga Dunaliella salina accumulates a high proportion of β-carotene during abiotic stress conditions. To better understand the intracellular flux distribution leading to carotenoid accumulation, this work aimed at reconstructing a carbon core metabolic network for D. salina CCAP 19/18 based on the recently published nuclear genome and its validation with experimental observations and literature data.ResultsThe reconstruction resulted in a network model with 221 reactions and 212 metabolites within three compartments: cytosol, chloroplast and mitochondrion. The network was implemented in the MATLAB toolbox CellNetAnalyzer and checked for feasibility. Furthermore, a flux balance analysis was carried out for different light and nutrient uptake rates. The comparison of the experimental knowledge with the model prediction revealed that the results of the stoichiometric network analysis are plausible and in good agreement with the observed behavior. Accordingly, our model provides an excellent tool for investigating the carbon core metabolism of D. salina.ConclusionsThe reconstructed metabolic network of D. salina presented in this work is able to predict the biological behavior under light and nutrient stress and will lead to an improved process understanding for the optimized production of high-value products in microalgae.

Bio-oil production from residual biomass of microalgae after lipid extraction: The case of Dunaliella Sp

Abstract Microalgae are known as the potential feedstock for production of bio based fuels due to their high lipid contents. Residual microalgae biomass after conversion of lipids into biodiesel can be converted into bio-oils in order to achieve complete exploitation of microalgae biomass in a microalgae biorefinery. Hydrothermal liquefaction (HTL) is a promising way for converting high-moisture biomass waste into high-energy crude oil. Therefore, this study intended to produce bio–oil from residual biomass of microalgae Dunaliella Sp. after lipid extraction by utilizing HTL as a biorefinery concept. HTL results showed that the average bio-oil yield was 11.81 w/w%, which was obtained at 350 °C, a residence time of 60 min and pressure of 200 bar. The results of CHNS analysis showed that crude oil produced by the HTL process in this study contains 4.82% nitrogen, 68.53% carbon, 1% hydrogen, 21.9% sulfur, which are within the permitted ranges.

Parameter Estimation for Dynamic Resource Allocation in Microorganisms: A Bi-level Optimization Problem

Given their key roles in almost all ecosystems and in several industries, understanding and predicting microorganism growth is of utmost importance. In compliance with evolutionary principles, coarse-grained or genome-scale models of microbial growth can be used to determine optimal resource allocation scheme under dynamic environmental conditions. Resource allocation approaches have given important qualitative results, but it still remains a gap towards quantitiative predictions. The first step in this direction is parameter calibration with experimental data. But fitting these models results in a bi-level optimization problem, whose numerical resolution involves complex optimization issues. As a case study, we present here a coarse-grained model describing how microalgae acclimate to a change in light intensity. We first determine using the Pontryagin maximum principle and numerical simulations the optimal strategy, corresponding to a turnpike with a chattering arc. Then, a bi-level optimization problem is proposed to calibrate the model with experimental data. To solve it, a classical parameter identification routine is used, calling at each iteration the bocop solver to solve the optimal control problem (by a direct method). The calibrated model is able to represent the photoacclimation dynamics of the microalga Dunaliella tertiolecta facing a down-shift of light intensity.

New aspects of application of microalgae Dunaliella Salina in the formula of enriched bread

The methods of mathematical planning of the experiment determined that the optimal dosages in the formulation of bread powder from microalgae Dunaliella Salina are 5.0-10.0 % by weight of flour in the dough. As a result of applying the recipe of promising new plant additives the organoleptic quality (taste, odor, status crumb) and physical-chemical parameters of the finished products (specific volume and porosity of bread crumb) improves. Due to the increased content of protein substances, including essential amino acids, dietary fibers, vitamins, minerals the bread has increased nutritional and biological value and can be considered as a product of therapeutic and preventive purposes. The range of functional bakery products is also expanding.

The ameliorating effect of carotenoid rich fraction extracted from Dunaliella salina microalga against inflammation- associated cardiac dysfunction in obese rats

The carotenoid rich fraction of microalgae Dunaliella salina (crf-DS) have been receiving great attention, due to they abilities to protect and improve various disorders. The objective of this study is to explore the therapeutic efficiency of crf-DS on obesity-assciated cardiac dysfunction in the high-fat diet (HFD) treated rats. These rats were orally administered with crf-DS (150 mg /kg body weight), for six consecutive weeks in comparison with reference drug(orlistat). Specific cardiac biomarkers were examined including; adiponectin, plasminogen activator inhibitor (PAI-1), glucagon, troponin-I (cTnI). The cell adhesion molecules (VCAM and ICAM), C-reactive protein (CRP), collagen type II (Col II), collagen alpha-1 (III) chain (Col3A1), lipoxygenase activity (LOX), as well as histopathological examination of cardiac tissue were investigated. Results indicated a significant reduction(P ≤ 0.05) in adiponectin and glucagon levels in serum of obese rats. However, cTnI, PAI-1, cell adhesion molecules, CRP, Col II, and Col3A1 and LOX levels declared marked increase. Histopathological examination of cardiac tissue showed fibrosis with severe congestion in the myocardial blood vessels. On the other hand, rats medicated with a crf-DS demonstrated noticeable ameliorating effect in all the measured parameters. Beside, myocardial tissue of obese rats showed no alteration. Hence, It could be concluded that, oral supplementation with crf-DS is able to attenuate cardiac dysfunction in obese rats. Further extended work is needed to exploit, the possible application of D. salina as nutraceuticals and food additives.

Metabolic responses of the green microalga Dunaliella salina to silver nanoparticles-induced oxidative stress in the presence of salicylic acid treatment

In the present study, the biochemical responses and antioxidant enzymes activity of the Dunaliella salina, a green microalga, to the interaction of silver nanoparticles (AgNPs) and salicylic acid (SA) were investigated. Algal suspensions in the phase of logarithmic growth were subjected to the concentrations of 0, 5, 15, and 25 pM AgNPs with or without 1 mM SA. AgNPs level of 25 pM declined cell division but highly accumulated levels of chlorophyll, β-carotene, proteins, free amino acid, carbohydrates, and hydrogen peroxide, which was associated with enhanced the activity of proteolysis, lipid peroxidation, and antioxidant enzymes. SA-treated cells at 25 pM AgNPs improved cell growth but declined the activities of antioxidant enzymes and proteolytic along with a lower accumulation of metabolites except β-carotene relative to untreated controls. These results suggest that AgNPs treatment induce oxidative stress in D. salina cells, which tolerated by alga through the metabolic modifications and accumulating β-carotene, while SA induces AgNPs tolerance by the mechanisms that direct carbon flux to growth and β-carotene biosynthesis rather than the antioxidant enzymes or osmoprotectant metabolites.

Adsorption of Radioactive Materials by Green Microalgae Dunaliella salina from Aqueous Solution

Introduction: Nuclear accidents release large quantities of radioactive materials into the environment. Iodine-131 and cesium-137 are two radionuclides released during nuclear accident, which can pose the greatest cancer risks. These radionuclides can be moved to other areas through rain and wind. The aim of this study was to develop efficient and economical biological methods for the absorption of water-soluble radionuclides released after a nuclear accident. Material and Methods: The exposure of the algae to an aqueous solution of I-131 radionuclide was performed for 1, 2, and 3 h. The concentration activities of the samples were 27 μCi/ml and 270 μCi/ml. After the removal of the alga by centrifuging, the activities of the sample solutions were measured using a calibrated dose calibrator. The measured activities at the mentioned periods of time were statistically significant for both groups (P<0.05). Results: The obtained results of the current study revealed that the activity of radioiodine-131 decreased 1, 2, and 3 h after adding algae, compared to the control group at the same time (21.8, 32.33, 39.84 for 27 μCi/ml and 15.38, 21.53, and 30 for 270 μCi/ml, respectively). Furthermore, radioactive iodine is absorbed very well with this type of algae. Conclusion: It can be concluded that Dunaliella salina can be used for the decontamination of radioiodine. This method can play a significant role in the decontamination of hazardous radioiodine after nuclear accidents. © 2019, Mashhad University of Medical Sciences.

MORPHOLOGICAL AND MORPHOMETRICAL FEATURES IN DUNALIELLA SALINA (CHLAMYDOMONADALES, DUNALIELLACEAE) DURING THE TWO-PHASE CULTIVATION MODE

The paper presents studies of morphological and morphometrical characteristics of green halophilic carotenogenic microalga Dunaliella salina (Dunal) Teodoresco, 1905, from the south-west region of Crimean Peninsula. D. salina was cultivated in two-phase mode under conditions of natural illumination at the premises of A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS (IBSS), Sevastopol, Russia. The maximum D. salina cell density was 1.69·106 cell/ml in the “green” phase and 0.84·106 cell/ml in the “red” growth phase. The maximum productivity by cell number reached 0.15 ∙ 106 cell/(ml·day)in the “green” phase while it was lower by 73% in the “red” phase (0.04∙106 cell/(ml·day). Along with the maximum productivity, linear growth stage in the first phase was characterized by a maximum fraction of small (up to 500 μm3 in volume) cells (about 15-29%) and a decrease in cell volume by 40-45% as compared with initial value. The mean of D. salina cell volume in the “red” phase was 30% higher than in the “green” phase. At the same time, the large cell fraction in the “red” phase was consistently high (15-35%). The patterns of change in morphological and morphometrical cell parameters were in accordance to stage and conditions of growth. Thus, cell elongation was noted in the stage of linear growth, while under unfavorable conditions at growth-declining stage cells became more round-shaped, with orange and tile-red coloration and granulation of cell content. It was shown that morphological and morphometric cell parameters can serve as additional criteria for assessment of physiological condition in D. salina culture. The experiment demonstrated the prospects for two-stage D. salina cultivation in Crimea.