Different Species Of Microalgae Research Articles

Removal of organic matter during adaptation of Nannochloropsis oculata in livestock waste

Microalgae, like plants, contribute significantly to the development of the oxygen biogeochemical cycle due to their high photosynthetic efficiency. In addition, they provide high yields of polyunsaturated fatty acids, sterols, proteins, terpenoids, and pigments, among others. Therefore, different species of microalgae have been studied and used on a laboratory scale to carry out processes such as wastewater treatment or aerobic bioconversion, which are presented as sustainable and viable alternatives for the treatment and recovery of organic waste (OW), usually rich in carbohydrates, lipids and proteins. In the present investigation, the removal of organic matter was evaluated during the adaptation of Nannochloropsis oculata in residues of poultry wastewater and swine origin, obtained from technical and semi-technical plants, respectively, located in the high mountain zone of the state of Veracruz, Mexico. The experiment was carried out in 250 mL discontinuous photobioreactors with a working volume of 200 mL, where 3 inoculum-substrate ratios were studied for each organic residue: 10, 15 and 20% inoculum in poultry wastewater (PWW) and 30, 50 and 70% inoculum in pig manure (PM). In addition, the conditions of temperature (20 ± 2 °C), illumination (2000 lx), photoperiod of 12/12 (light/dark) and continuous aeration were controlled. It was shown that N. oculata can tolerate alkaline conditions of pH ≥ 10 and contributes to the reduction of soluble organic matter in OW. PWW and PM were found to be viable media for the survival of N. oculata. Finally, regarding the inoculum concentrations studied, the most appropriate were 10% for PWW and 70% for PM.

Comparing the removal efficiency of diisobutyl phthalate by Bacillariophyta, Cyanophyta and Chlorophyta

The utilization of microalgae for both removing phthalate esters (PAEs) from wastewater and producing bioenergy has become a popular research topic. However, there is a lack of studies comparing the effectiveness of different types of microalgae in removing these harmful compounds. Therefore, the present study aimed to evaluate and compare the efficiency of various processes, such as hydrolysis, photolysis, adsorption, and biodegradation, in removing diisobutyl phthalate (DiBP) using six different species of microalgae. The study indicated that the average removal efficiency of DiBP (initial concentrations of 5, 0.5, and 0.05 mg L−1) by all six microalgae (initial cell density of 1 × 106 cells mL−1) was in the order of Scenedesmus obliquus (95.39 %) > Chlorella vulgaris (94.78 %) > Chroococcus sp. (91.16 %) > Cyclotella sp. (89.32 %) > Nitzschia sp. (88.38 %) > Nostoc sp. (84.33 %). The results of both hydrolysis and photolysis experiments revealed that the removal of DiBP had minimal impact, with respective removal efficiencies of only 0.89 % and 1.82 %. The adsorption efficiency of all six microalgae decreased significantly with increasing initial DiBP concentrations, while the biodegradation efficiency was elevated. Chlorella vulgaris and Chroococcus sp. demonstrated the highest adsorption and biodegradation efficiencies among the microalgae tested. Scenedesmus obliquus was chosen for the analysis of the degradation products of DiBP due to its exceptional ability to remove DiBP. The analysis yielded valuable results, identifying monoisobutyl phthalate (MiBP), phthalic acid (PA), and salicylic acid (SA) as the possible degradation products of DiBP. The possible degradation pathways mainly included dealkylation, the addition of hydroxyl groups, and decarboxylation. This study lays a theoretical foundation for the elimination of PAEs in the aquatic environment.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ МОРФОМЕТРИЧЕСКИХ ХАРАКТЕРИСТИК МИКРОВОДОРОСЛЕЙ РОДА DUNALIELLA ИЗ ГИПЕРСОЛЕНЫХ ОЗЕР КРЫМА

Genus of microalgae Dunaliella includes a large number of species greatly differing by its product potential, but being similar by general physical appearance. In fact, different Dunaliella species differ much by cell shape and size. The algae cell can be ellipsoid, ovoid, almost spherical, pear-shaped or fusiform. Cell size is variable even within a species, and differences are related to growth conditions, such as the amount of nutrients, light intensity, and salt concentration. Morphometric and phylogenetic analyses are necessary to identify the taxonomic status of different species of microalgae of the genus Dunaliella. The aim of the work is a morphometric analysis of wild strains of microalgae of the genus Dunaliella from hypersalted lakes of the Crimea: Sasyk-Sivash, Saki, Moynak and Ajigol. With the help of the FlowCam 8400 visualizing flow cytometer, four populations were studied, about 10 thousand cells were analyzed in each, 8 morphological parameters were evaluated. The results were processed using a program for statistical data processing R. To assess the degree of separability of D. salina cells and to construct the corresponding discriminating function, the method of linear discriminant analysis was used. Applying a step-by-step algorithm for constructing a discriminant function, an optimal set of the most indicative morphometric characteristics sufficient to divide a set of cells into groups according to their belonging to a particular reservoir was established.

Multi-Objective Optimization of Microalgae Metabolism: An Evolutive Algorithm Based on FBA.

Studies enabled by metabolic models of different species of microalgae have become significant since they allow us to understand changes in their metabolism and physiological stages. The most used method to study cell metabolism is FBA, which commonly focuses on optimizing a single objective function. However, recent studies have brought attention to the exploration of simultaneous optimization of multiple objectives. Such strategies have found application in optimizing biomass and several other bioproducts of interest; they usually use approaches such as multi-level models or enumerations schemes. This work proposes an alternative in silico multiobjective model based on an evolutionary algorithm that offers a broader approximation of the Pareto frontier, allowing a better angle for decision making in metabolic engineering. The proposed strategy is validated on a reduced metabolic network of the microalgae Chlamydomonas reinhardtii while optimizing for the production of protein, carbohydrates, and CO uptake. The results from the conducted experimental design show a favorable difference in the number of solutions achieved compared to a classic tool solving FBA.

Improving the Nutritional, Structural, and Sensory Properties of Gluten-Free Bread with Different Species of Microalgae.

Microalgae are an enormous source of nutrients that can be utilized to enrich common food of inherently low nutritional value, such as gluten-free (GF) bread. Addition of the algae species: Tetraselmis chuii (Tc), Chlorella vulgaris (Cv), and Nannochloropsis gaditana (Ng) biomass led to a significant increase in proteins, lipids, minerals (Ca, Mg, K, P, S, Fe, Cu, Zn, Mn), and antioxidant activity. Although, a compromise on dough rheology and consequential sensory properties was observed. To address this, ethanol treatment of the biomass was necessary to eliminate pigments and odor compounds, which resulted in the bread receiving a similar score as the control during sensory trials. Ethanol treatment also resulted in increased dough strength depicted by creep/recovery tests. Due to the stronger dough structure, more air bubbles were trapped in the dough resulting in softer breads (23–65%) of high volume (12–27%) vs. the native algae biomass bread. Breads baked with Ng and Cv resulted in higher protein-enrichment than the Tc, while Tc enrichment led to an elevated mineral content, especially the Ca, which was six times higher than the other algae species. Overall, Ng, in combination with ethanol treatment, yielded a highly nutritious bread of improved technological and sensory properties, indicating that this species might be a candidate for functional GF bread development.

Exopolysaccharides frommicroalgae: production, characterization, optimization and techno-economic assessment.

Microalgae cultivation for exopolysaccharide production has getting more attention as a result of their high hydrocarbon biosynthesis skill. The aim of this study is to examine the exopolysaccharide production potential of different species of microalgae. In this context, exopolysaccharides were produced from Chlorella minutissima, Chlorella sorokiniana and Botryococcus braunii microalgae and the effects of carbon and nitrogen content in the growth medium and illumination time on exopolysaccharide production were analyzed statistically using Box-Behnken experimental design. In addition, techno-economic assessment of exopolysaccharide production were also performed by using the most productive microalgae and optimum conditions determined in this study. As a result of the experiments, it was seen that C. minutissima, C. sorokiniana and B. braunii produced 0.245 ± 0.0025g/L, 0.163 ± 0.0016g/L and 0.117 ± 0.0007g/L exopolysaccharide, respectively. Statistically, it was observed that there was an inverse relationship between the exopolysaccharide production and investigated parameters such as illumination period and carbon and nitrogen amounts of culture mediums. The techno-economic assessment comprising microalgal exopolysaccharide (EPS) bioprocess was carried out, and it showed that the system can be considered economically viable, yet can be improved with biorefinery approach.

Identification of Microplastics Based on the Fractal Properties of Their Holographic Fingerprint

Water plastic pollution is a serious problem affecting sealife, marine habitats, and the food chain. Artificial intelligence-enabled coherent imaging has recently shown exciting advances in the field of environmental monitoring, and portable holographic microscopes are good candidates to map the microparticles content of marine waters. The “holographic fingerprint” due to coherent light diffraction is rich in information, fully encoded into the complex wavefront scattered by the sample. Hence, proper analysis of the wavefronts reconstructed from digital holograms can unlock new possibilities in the fields of diagnostics and environmental monitoring. Fractal geometry well describes natural objects and allows inferring added-value information on the way these fill 2D spaces and 3D volumes. The most abundant micron-scale class of objects that populate marine waters consists of microalgae named diatoms, which are of interest as bioindicators of water quality. Here we investigate the fractal properties of holographic patterns of diatoms and microplastics, considering a heterogeneous mixture of five types of plastic materials and 55 different species of microalgae. We show that, different from the case of weak scattering objects, a small set of fractal parameters is able to characterize these two large ensembles. As an applicative example, we carry out classification tests to show the possibility to identify the two classes with high accuracy. This new holographic fractal description of scattering micro-objects could be used in the near future for in situ automatic mapping of microplastic pollutants and for taxonomy of diatoms as water quality bioindicators, screened onboard holographic systems.

A co-cultivation process of Nannochloropsis oculata and Tisochrysis lutea induces morpho-physiological and biochemical variations potentially useful for biotechnological purposes

The biotechnological potential of microalgae has gained considerable importance in many applied fields: biomass production for food and feed, cosmeceutical and pharmaceutical products, energy and phytoremediation. The driving force that inspires the progress in microalgae production is the need for new cultivation systems to obtain simultaneously the maximum yield, reduction of water and nutrients use, and production of economically interesting molecules, such as pigments, fatty acids and polysaccharides. We aim to test, for the first time, the co-cultivation in saline medium of Tisochrysis lutea (Haptophyta) and Nannochloropsis oculata (Ochrophyta) to obtain valuable compounds, i.e. pigments and lipids characteristic of each species, using a single culture process. Mono-cultures of each strain were used as controls. The two strains showed an increase in the concentration of chlorophylls and carotenoids in co-culture. At the end of the experiment, the fatty acid profile was analysed by gas chromatography–mass spectrometry. The lipids in the co-cultivated cell extracts were mainly attributable to N. oculata, which represented 97% of the total cells (ca. 83% of the total biomass) at the end of the experiment. Nevertheless, the ω-3 characteristic of T. lutea (DHA and SDA, absent in N. oculata) was also detectable. Although the co-cultivation of these two phylogenetically different species of microalgae did not show positive effects on the growth and on the total lipid production, however, this process resulted in a reduction of the production costs and a lower consumption of water and nutrients.

In vitro Assessment of Bacterial Strains Associated with Microalgae as Potential Probiotics

Bacteria and microalgae are essential elements in the aquatic ecosystem, co-existing and having constant interactions with each other which help microalgae to exert its beneficial effect as probiotics in aquaculture. This research aims to isolate and identify potential probiotics from different species of microalgae and to evaluate their antimicrobial activity against pathogenic Vibrio spp. via series of in vitro assays; disc diffusion, well diffusion, and co-culture assays. A total of 18 bacterial strains were isolated from five species of microalgae; Chlorella sp., Nannochloropsis sp., Amphora sp., Chaetoceros sp., and Spirulina sp.. The isolated strains were tested in in vitro antagonistic assay against four Vibrio spp. (Vibrio harveyi, Vibrio alginolyticus, Vibrio vulnificus, and Vibrio parahaemolyticus). Seventeen strains demonstrated antimicrobial activity with the highest inhibition was observed by strain SPS11 against V. parahaemolyticus (12.6 ± 0.36 mm) in disc diffusion assay and strain NAS32 showed 13.2 ± 0.45 mm clear zone against V. vulnificus in well diffusion assay. In co-culture assay, both the SPS11 and NAS32 were able to reduce the growth of V. parahaemolyticus and V. harveyi at concentration of 106 and 108 CFU mL-1, respectively. Strains SPS11 and NAS32 were characterized as gram positive bacteria with rod shape and further identified as Lysinibacillus fusiformis (SPS11) and Lysinibacillus sphaericus (NAS32) using 16s rRNA. These two strains should be further studied in in vivo challenged experiments in fish and shellfish to explore their probiotic effects.

Effect of the inclusion of microalgae on the physical properties of extruded feed for gilthead seabream (Sparus aurata L.)

The inclusion of new ingredients in fish feed can affect the physical quality of the pellets. In order to study the effect of the addition of microalgae on the physical properties of the pellets, 15 extruded diets were studied that included three different species of microalgae (Nannochloropsis gaditana, Tetraselmis chuii and Chlorella vulgaris) at five different inclusion levels (0, 2.5, 5, 10 and 15%). The feed mixtures were extruded using a single-screw extruder (barrel temperature profile: 90–95–100 °C; die temperature: 105 °C; screw speed: 40–50 rpm). The physical properties studied included: expansion ratio, density, hardness, pellet durability index, water absorption index, water solubility index, floatability, sinking velocity, fat leakage and starch gelatinization. The present study showed that the physical properties of the pellets are influenced by the type and amount of microalgae used. The physical quality of the feed was modified, generally increasing its hardness and durability and reducing the fat leakage.

An Innovative Low-Cost Equipment for Electro-Concentration of Microalgal Biomass

Microalgal harvesting is one of the most challenging processes in the development of algal research and development. Several methods, such as centrifugation, flocculation and filtration, are available at the laboratory scale. However, the requirement for expensive pieces of equipment and the possibility of biomass contamination are recurring gaps that hinder the development of microalgae R&D (research and development) in different parts of the world. Recently, electroflotation has been proved to be a suitable method for the harvesting of different species of microalgae and cyanobacteria. To this day, there are no companies that sell laboratory-scale electroflotation equipment; this is mainly due to the gap in the knowledge of which factors (time, mixing rate, number of electrodes and others) will affect the efficiency of concentration without reducing the biomass quality. This paper aims to build an innovative, low-cost electroflotation system for under 300 USD (United States dollar) with cheap and resistant materials. To achieve our goal, we tested the interaction of three variables (time, mixing rate and amount of electrodes). Results showed that an efficiency closer to 100% could be achieved in under 20 min using > 10 electrodes and 150 rpm (round per minute). We hope this innovative approach can be used by different researchers to improve our knowledge of the concentration and harvesting of algae and cyanobacteria.

Ectoine from Bacterial and Algal Origin Is a Compatible Solute in Microalgae.

Osmoregulation in phytoplankton is attributed to several highly polar low-molecular-weight metabolites. A widely accepted model considers dimethylsulfoniopropionate (DMSP) as the most important and abundant osmotically active metabolite. Using an optimized procedure for the extraction and detection of highly polar metabolites, we expand the group of phytoplankton osmolytes by identifying ectoine in several microalgae. Ectoine is known as a bacterial compatible solute, but, to the best of our knowledge, was never considered as a phytoplankton-derived product. Given the ability of microalgae to take up zwitterions, such as DMSP, we tested the hypothesis that the algal ectoine is derived from associated bacteria. We therefore analyzed methanol extracts of xenic and axenic cultures of two different species of microalgae and could detect elevated concentrations of ectoine in those that harbor associated bacteria. However, also microalgae without an associated microbiome contain ectoine in smaller amounts, pointing towards a dual origin of this metabolite in the algae from their own biosynthesis as well as from uptake. We also tested the role of ectoine in the osmoadaptation of microalgae. In the model diatoms Thalassiosira weissflogii and Phaeodactylum tricornutum, elevated amounts of ectoine were found when cultivated in seawater with salinities of 50 PSU compared to the standard culture conditions of 35 PSU. Therefore, we add ectoine to the family of osmoadaptive metabolites in phytoplankton and prove a new, potentially synergistic metabolic interplay of bacteria and algae.

Interaction between microalgae, marine snow and anionic polyacrylamide APAM at marine conditions

When an oil field ages and the pressure in the reservoir decreases, or for oil fields with heavy oil, there may be a need for enhanced oil recovery (EOR) technologies. Polymer injection is a water-based EOR method where the viscosity of the water injected for pressure support is increased by mixing with a high concentration polymer solution. In this project, the potential fate of a synthetic anionic polyacrylamide (APAM) in seawater was investigated, since these EOR polymers may enter the marine environment with the produced water (PW). The main objective of the study was to determine if the APAM will interact with cells or aggregates (marine snow) of microalgae, resulting in potential polymer transport from the euphotic zone to the seabed. Three different species of microalgae with different degree of autotrophy (autotroph, mixotroph and heterotroph) were exposed to fluorescence-tagged APAM. Attachment to algal cells or aggregates formed by active or heat-inactivated algae were analysed by fluorescence microscopy and fluorometry. Our results suggested that attachment of APAM to cells of the algal species included in his study was negligible. A carousel system with natural seawater (SW) was used for formation of algal aggregates, one of the key components of marine snow. When aggregates of the diatom Thalassiosira rotula were formed in the presence of the fluorescence-tagged APAM, and at SW temperatures relevant for the Norwegian Continental Shelf, the polymer was nearly exclusively measured in the water phase after separation from the aggregates. The aggregate measurements therefore confirmed the results from the attachment studies, and we found no evidence of accumulation of APAM in aggregates formed from algae. Marine snow from algae is therefore not expected to significantly contribute to sedimentation of APAM dissolved in the water column.

Изменчивость размерных характеристик и выживаемости науплиусов крымских артемий Artemia spp. (Branchiopoda: Anostraca) при питании микроводорослями разных видов

Науплиусы жаброногих рачков Artemia spp. (Branchiopoda: Anostraca) ― один из основных видов живых кормов, применяемых при культивировании личинок морских рыб. Для улучшения биохимического состава артемий их насыщают специализированными искусственными смесями или микроводорослями, содержащими незаменимые для личинок рыб компоненты. Размеры, скорость роста и выживаемость науплиусов (N) и метанауплиусов (MN) артемии могут иметь большое значение при их использовании в качестве живого корма. Цель настоящей работы ― выполнить сравнительный анализ размерных характеристик и выживаемости науплиусов крымских артемий производства компании Artemia cysts при питании разными видами микроводорослей. Науплиусы артемии получили в соответствии с общепринятой методикой. В качестве корма использовали следующие виды микроводорослей: Isochrysis galbana, Prorocentrum micans, Gymnodinium wulffii, Prorocentrum cordatum, Tetraselmis suecica, Phaeodactylum tricornutum. Средний диаметр сухих цист артемий составил 0,230 мм. Средние значения длины и ширины ортонауплиусов артемий ― 0,473 и 0,150 мм соответственно. Односуточные MN, питавшиеся T. suesica, имели достоверно меньшие средние значения длины [(0,698 ± 0,014) мм], чем MN, питавшиеся I. galbana, P. micans, G. wulfii и Ph. tricornutum (P < 0,05). Двух- и трёхсуточные MN, питавшиеся I. galbana, имели достоверно бόльшие средние значения длины и ширины (двухсуточные ― 1,19 и 0,324 мм; трёхсуточные ― 1,53 и 0,47 мм соответственно), чем MN, питавшиеся Ph. tricornutum, T. suesica, P. micans и P. cordatum. Среди всех метанауплиусов, насыщавшихся микроводорослями, минимальные средние значения длины имели MN, питавшиеся P. cordatum. Выживаемость метанауплиусов при насыщении P. cordatum, P. micans и T. suecica была максимальной (выше 95 %). Сочетание небольших размеров и высокой выживаемости метанауплиусов, питавшихся P. cordatum (микроводоросль со значительным содержанием докозагексаеновой и эйкозапентаеновой кислот), предполагает их использование в качестве перспективного живого корма для личинок морских рыб.

Nutritional value changes in response to temperature, microalgae mono and mixed cultures

Abstract Aim The response of mixed cultures and monocultures of Pseudopediastrum boryanum (Turpin) E. Hegewald and Scenedesmus obliquus (Turpin) Kützing was assessed in the laboratory at three different temperatures: 20, 30 and 40 °C. The change in biomass and biochemical composition of these cultures was evaluated. Methods Microalgae were placed in a batch culture over 21-days in ASM1 medium. Cell density was directly counted every two days using a Fuchs-Rosenthal hemocytometer. Chlorophyll ‘a’ and total carotenoids were extracted twice. Protein, carbohydrate, total lipid and fatty acid contents were determined at the end of the experiment. Results Cultures grown in 40 °C exhibited no growth. However, there was increased cell density (13.6 x 106 cell.mL-1) and biomass (55 g.L-1) in the S. obliquus monoculture at 30 °C. High protein concentrations (672.6 mg.g-1) were observed in monocultures P. boryanum and S. obliquus at 20 °C treatments. There were high carbohydrate concentrations (6.17 mg.g-1) in P. boryanum unialgal at 30 °C. There was no significant difference in total lipid content between S. obliquus (95.5 mg.g-1), P. boryanum (96.3 mg.g-1) and the mixed culture at 20 °C (105.3 mg.g-1). FAMEs varied significantly regarding the number of unsaturated components, which predominantly consisted of fatty acids with two or more unsaturated bonds. Conclusions The biomass of the treatments analyzed was rich in proteins and essential fatty acids (such as linolenic acid), yet low in carbohydrate content, suggesting its potential use as a food supplement. Our results indicate that mixed culture of P. boryanum and S. obliquus was inefficient in cultivating biomass or biochemical compounds as compared to the unialgal cultivations. However, algae grown together showed better stability in their biochemical composition in response to changes in temperature, an important factor for microalgae production in open ponds and in food safety measures. These results suggest the consortia among different species of microalgae should be tested to determine better methodologies for the production of biomass and metabolites with greater stability towards environmental factors.

Microalgae as a source of vitamin K1

Vitamin K1 has recently been identified as a potentially important nutrient for prevention of chronic diseases, especially those associated with aging, like osteoporosis and cardiovascular disease. Currently the majority of Vitamin K1 is produced via chemical synthesis; the aim of this work is to examine the potential to produce Vitamin K1 using microalgae. Biological synthesis produces only the active E-isomer, whereas chemical synthesis produces 10–20% of the inactive Z-isomer. Biosynthesis also utilises mild operating conditions, sustainable production methods, and has the potential to simultaneously produce other beneficial compounds. Seven different species of microalgae were screened; the cyanobacterium Anabaena cylindrica was identified as the richest source of vitamin K1. Concentrations were of the order 200 μg g−1 on a dry-weight basis, which is around six times higher than rich dietary sources such as spinach and parsley; one gram of the algae provides approximately three times the daily adult intake for Vitamin K1. By optimizing the growth conditions (lighting and medium), the productivity was increased fourfold to 22 μg L−1 d−1. Analysis of the nutritional properties of the biomass revealed that it contained high levels of protein (69% (w/w)) and Vitamin B12 (1.5 μg g−1), in addition to the high concentration of phylloquinone. An animal study was performed to evaluate the potential toxicity of the biomass; however, no evidence of acute toxicity was observed even at relatively high addition rates (15% (w/w)). These results support the use of microalgae, specifically A. cylindrica, as a source of phylloquinone.

Thermal degradation of carbohydrates, proteins and lipids in microalgae analyzed by evolutionary computation

The kinetics of microalgae pyrolysis is investigated to analyze the thermal degradation of carbohydrates, proteins and lipids in different species of microalgae. The pyrolysis processes of microalgae Chlorella vulgaris ESP-31, Nannochloropsis oceanica CY2, and Chlamydomonas sp. JSC4 are examined by thermogravimetric analysis (TGA), and independent parallel reaction (IPR) model is adopted to approach the pyrolysis kinetics. To maximize the fit quality between the established kinetic models and experimental data, particle swarm optimization (PSO), a kind of evolutionary computation, is employed. The thermal degradation characteristics of the three microalgal species are compared with each other. The results suggest that the thermal degradation curves of the three microalgae can be predicted with a fit quality of at least 97.9%. The activation energies of carbohydrates, proteins, and lipids in the microalgae are in the ranges of 53.28–53.30, 142.61–188.35, and 40.21–59.23 kJ mol−1, respectively, while the thermal degradation of carbohydrates, proteins, and lipids are in temperature ranges of 164–497, 209–309, and 200–635 °C, respectively. It is proved in this work that the IPR model and the calculation of the PSO can be used to predict the pyrolysis kinetics of microalgae to a good level of fitness.

A comparison of the morphological and biochemical characteristics of Chlorella sorokiniana and Chlorella zofingiensis cultured under photoautotrophic and mixotrophic conditions.

The responses of two species of microalgae, Chlorella sorokiniana and Chlorella zofingiensis, were compared regarding their morphological and biochemical properties under photoautotrophic and mixotrophic conditions. These microalgae were cultured under both conditions, and their crude ethanolic extracts were examined for their pigment and total phenolic contents. In addition, the microalgae’s antioxidant activities were determined using a DPPH radical scavenging assay and a ferric reducing antioxidant power (FRAP) assay. Both strains showed increases in cell size due to the accumulation of lipid bodies and other cell contents, especially carotenoids, under the mixotrophic condition. Notably, reductions in phenolic and chlorophyll contents were observed to be associated with lower antioxidant activity. C. zofingiensis compared with C. sorokiniana, demonstrated higher antioxidant activity and carotenoid content. This study showed that different species of microalgae responded differently to varying conditions by producing different types of metabolites, as evidenced by the production of higher levels of phenolic compounds under the photoautotrophic condition and the production of the same levels of carotenoids under both photoautotrophic and mixotrophic conditions.

Screening of some Naturally Isolated Microalgal Strains for Polyunsaturated Fatty Acids Production

Background and Purpose: Nowadays, polyunsaturated fatty acids (PUFAs) are playing a great role in human wellbeing and health improvement. A wide spectrum of biological, medical and health benefit effects ranging from cardiovascular, neuronal, anticancer and antioxidant have been reported from different PUFAs in human. Methodology: In this study, six different species of microalgae belonging to the chlorophyta and cyanobacteria phylum were isolated from soil and water samples collected from Persian Gulf. Their growth rate, biomass and lipid production and productivity and more importantly their ability to produce PUFAs was investigated. Results: The isolated species represented a great fatty acid profile including many different polyunsaturated fatty acids (PUFAs) ranging from 6-20 carbon atoms. S. obliquus and N. muscorum proven to have a better profile for PUFAs production, whilst C. vulgaris could be considered as a more robust strain to produce other fatty acid classes. Besides, C. vulgaris with its higher growth rates (0.39 d-1)and S. obliquus owing to its higher total lipid content (43.92%) seems more interesting strains for scale up studies. Conclusion: The obtained results demonstrated the great potential of naturally isolated strains of microalgae for PUFA production and provided some insights in next studies to explore more producing strains.

Recovery of Functional Pigments from four Different Species of Microalgae

In the present work, four species of microalgae: Spirulina platensis (SP), Chlorella vulgaris (CV), Haematococcus pluvialis (HP), and the diatom Phaeodactylum tricornutum (PT) were selected as raw materials for the recovery of multifunctional extracts. Ultrasonic assisted extraction (UAE) using different solvents was applied under specific optimized conditions. Organic solvents such as hexane, acetone and ethanol, as well as food grade solvents, such as limonene, MCT oil, soybean oil and phosphate buffer (pH= 7) were used. The total carotenoid, β-carotene and chlorophyll a content in the extracts was determined for all species using UV-Vis spectrometry. Moreover, in the case of SP the phycocyanin content was also measured. The extracts were evaluated regarding their antiradical activity using the DPPH method. Taking into consideration the nature of the solvent used and the total pigment content, acetone and ethanol can be replaced by limonene for the extraction of total carotenoids from HP and PT. For the extraction of phycocyanin from SP, water was considered the most efficient solvent. Ethanol extracts of CV were found rich in β-carotene. The DPPH assay revealed that HP and PT biomass exhibited the highest antiradical activity which can be recovered using suitable solvents.