Different Strains Of Microalgae Research Articles

Microalgal biofilm induces larval settlement in the model marine worm Platynereis dumerilii.

A free-swimming larval stage features in many marine invertebrate life cycles. To transition to a seafloor-dwelling juvenile stage, larvae need to settle out of the plankton, guided by specific environmental cues that lead them to an ideal habitat for their future life on the seafloor. Although the marine annelid Platynereis dumerilii has been cultured in research laboratories since the 1950s and has a free-swimming larval stage, specific environmental cues that induce settlement in this nereid worm are yet to be identified. Here, we demonstrate that microalgal biofilm is a key settlement cue for P. dumerilii larvae, inducing earlier onset of settlement and enhancing subsequent juvenile growth as a primary food source. We tested the settlement response of P. dumerilii to 40 different strains of microalgae, predominantly diatom species, finding that P. dumerilii have species-specific preferences in their choice of settlement substrate. The most effective diatom species for inducing P. dumerilii larval settlement were benthic pennate species including Grammatophora marina, Achnanthes brevipes and Nitzschia ovalis. The identification of specific environmental cues for P. dumerilii settlement enables a link between its ecology and the sensory and nervous system signalling that regulates larval behaviour and development. Incorporation of diatoms into P. dumerilii culture practices will improve the husbandry of this marine invertebrate model.

The Effect of Salinity Stress on the Antibacterial Activity of SpirulinaPlatensis Algae

Background: The production of secondary metabolites in different strains of microalgae varies and is likely dependent on environmental conditions. Consequently, the production of bioactive substances as secondary metabolites occurs in microalgae to aid their survival in adverse environmental conditions such as salinity stress. Objectives: The purpose of this study is to investigate the antibacterial activity of the methanolic extract of S. platensis algae cultivated under different salinity stresses against Yersinia rukeri, Escherichia coli, Salmonella sp., and Vibrio cholerae. Methods: The broth microdilution method was used to evaluate the growth inhibitory activity of the extracts against Yersinia ruckeri, Salmonella sp., Escherichia coli, and Vibrio cholerae bacteria. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined by this method, and the diameter of the inhibition zone was assessed through the well diffusion method. Results: In the treatment with algae extract grown under 3.5 ppt salinity stress, the concentrations of 50 and 25 mg/mL extract showed the largest inhibition zone diameter against Salmonella sp. compared to other bacteria. Under 7 ppt salinity stress, all studied concentrations of algal extract exhibited a higher inhibition zone diameter against V. cholerae compared to other bacteria. The results of comparing different concentrations of algae extract between the two salinity stresses of 3.5 and 7 ppt for each bacterium showed a significant difference (P < 0.05). As salinity increased, the diameter of the inhibition zone also increased for all bacteria. Conclusions: Our results showed an increase in the antibacterial activity of the methanolic extract of Spirulina platensis with higher salinity stress levels. Therefore, cultivating Spirulina algae in salt water can be a cost-effective and suitable method to produce more secondary metabolites for use in the pharmaceutical industry.

Green Synthesis of Bioplastics from Microalgae: A State-of-the-Art Review.

The synthesis of conventional plastics has increased tremendously in the last decades due to rapid industrialization, population growth, and advancement in the use of modern technologies. However, overuse of these fossil fuel-based plastics has resulted in serious environmental and health hazards by causing pollution, global warming, etc. Therefore, the use of microalgae as a feedstock is a promising, green, and sustainable approach for the production of biobased plastics. Various biopolymers, such as polyhydroxybutyrate, polyurethane, polylactic acid, cellulose-based polymers, starch-based polymers, and protein-based polymers, can be produced from different strains of microalgae under varying culture conditions. Different techniques, including genetic engineering, metabolic engineering, the use of photobioreactors, response surface methodology, and artificial intelligence, are used to alter and improve microalgae stocks for the commercial synthesis of bioplastics at lower costs. In comparison to conventional plastics, these biobased plastics are biodegradable, biocompatible, recyclable, non-toxic, eco-friendly, and sustainable, with robust mechanical and thermoplastic properties. In addition, the bioplastics are suitable for a plethora of applications in the agriculture, construction, healthcare, electrical and electronics, and packaging industries. Thus, this review focuses on techniques for the production of biopolymers and bioplastics from microalgae. In addition, it discusses innovative and efficient strategies for large-scale bioplastic production while also providing insights into the life cycle assessment, end-of-life, and applications of bioplastics. Furthermore, some challenges affecting industrial scale bioplastics production and recommendations for future research are provided.

Impacts of Fortifying Nile Tilapia (Oreochromis niloticus) Diet with Different Strains of Microalgae on Its Performance, Fillet Quality and Disease Resistance to Aeromonas hydrophila Considering the Interplay between Antioxidant and Inflammatory Response.

The oxidative stress facing fish during intensive production brings about diseases and mortalities that negatively influence their performance. Along with that, the increased awareness of omega-3 polyunsaturated fatty acids (omega-3-PUFAs) health benefits has been triggered the introduction of alternative additives in aqua feed that cause not only modulation in fish immune response but also fortification of their fillet. In this context, the role of microalgae mix (NSS) containing Nannochloropsis oculate and Schizochytrium and Spirulina species, which were enriched with bioactive molecules, especially EPA and DHA, was assessed on Nile tilapia's performance, fillet antioxidant stability, immune response, and disease resistance. Varying levels of NSS (0.75, 1.5, and 3%) were added to Nile tilapia's diet for 12 weeks and then a challenge of fish with virulent Aeromonas hydrophila (A. hydrophila) was carried out. Results showed that groups fed NSS, especially at higher levels, showed an improved WG and FCR, which corresponded with enhanced digestive enzymes' activities. Higher T-AOC was detected in muscle tissues of NSS3.0% fed fish with remarkable reduction in ROS, H2O2, and MDA contents, which came in parallel with upregulation of GSH-Px, CAT, and SOD genes. Notably, the contents of EPA and DHA in fillet were significantly increased with increasing the NSS levels. The mean log10 counts of pathogenic Vibrio and Staphylococcus species were reduced, and conversely, the populations of beneficial Lactobacillus and Bacillus species were increased more eminent after supplementation of NSS3.0% and NSS1.5%. Moreover, regulation of the immune response (lysozyme, IgM, ACH50, NO, and MPO), upregulation of IL-10, TGF-β, and IgM, and downregulation of IL-1β, TNF-α, HSP70,and COX-2 were observed following dietary higher NSS levels. After challenge, reduction in A. hydrophila counts was more prominent, especially in NSS3.0% supplemented group. Taken together, the current study encourages the incorporation of such microalgae mix in Nile tilapia's diet for targeting maximum performance, superior fillet quality, and protection against A. hydrophila.

CO2 sequestration: microalgae genome analysis and its application of effective green source technology

Microalgae genome technology for CO2 sequestration is an appropriate vehicle for articulating the importance of the current need and solution for reduction of CO2 at the atmospheric level. In comparison with C4 plants, microalgae have greater capability to fix atmospheric CO2.The rate of CO2 fixation differs in different strains of microalgae. The photosynthetic enzyme RuBisCO is widely responsible for photosynthetic carbon assimilation in all plants including phototrophic algae.The gene rbcL encodes this enzyme. The catalytic activity of carbonic anhydrase achieves the CO2 generation in the RuBisCO. CAH3 gene is essential for generating CO2 concentration for RuBisCO by dehydration of accumulated inorganic carbon. There are also few other microalgae genes which involves for carbon assimilation. Genomic resource databases and several other nucleotide databases are being used for sequencing the microalgal genomes. Even though, recent advances in genomic studies are providing thrust to enhance the research on microalgal species, they are expensive and resources available for microalgal genomic studies are limited. This review article attempts first as a combined revise on microalgae CO2 sequestration in the field of basic science, applied aspects, and the role of specific gene(s) in the algal system is well defined which could be a supportive involvement of carbon dioxide reduction as “Green-Gene Technology”. This Green biotechnology could be used for Global warming reduction as well as creating wealth from the waste through valuable by-products from the selected microalgae strains in future.

Isolation, mass cultivation, and biodiesel production potential of marine microalgae identified from Bay of Bengal.

In this study, marine microalgae were isolated from the Bay of Bengal, and their biodiesel production potential was investigated. Five different strains of microalgae were identified, viz. Nannochloropsis salina (N. salina), Dunaliella salina (D. salina), Chaetoceros calcitrans (C. calcitrans), Tetraselmis chuii (T. chuii), and Euglena sanguinea (E. sanguinea). Further, these stains were mass cultivated in a 250-L bioreactor to assess their biomass production ability. At the end of the exponential phase, algal biomass was harvested for lipid extraction. The fatty acid profile and physico-chemical properties of the lipids were analyzed. It was observed that a maximum of 27.67wt% of lipid was obtained for N. salina followed by D. salina (22.58 wt%), E. sanguinea (21.88 wt%), T. chuii (20.15 wt%), and C. calcitrans (16.25 wt%). Subsequently, the extracted lipids were subjected to single-step esterification and transesterification process to produce biodiesel by using an acid catalyst. The different parameters influencing the reaction such as catalyst concentration, temperature, methanol to lipid molar ratio, and time were investigated. A maximum biodiesel yield of 97, 94, 96, 92, and 92 wt% were obtained for N. salina, D. salina, C. calcitrans, T. chuii, and E. sanguinea, respectively, at the favorable reaction conditions. The fuel properties of biodiesel were analyzed as per the standard protocol and compared with ASTM D6751 standard.

Phytoremediation of 137Cs, 60Co, 241Am, and 239Pu from aquatic solutions using Chlamydomonas reinhardtii, Scenedesmus obliquus, and Chlorella vulgaris

This work is focused on the phytoremediation of radionuclides using eukaryotic green microalgae Chlamydomonas reinhardtii, Scenedesmus obliquus, and Chlorella vulgaris. This study highlights the potential use of microalgae in the process of phytoremediation in polluted aquatic solutions due to the unique cellular mechanism of uptake of different radionuclides. The kinetics of radionuclide removal from the samples was described according to the first-order kinetics and expressed by the rate constant k and calculated for each microalga at the most suitable pH. The activity of 137Cs and 60Co was measured in the presence of S. obliquus or C. reinhardtii and the activity of 241Am and 239Pu was measured in the presence of C. vulgaris. A significant decrease of activity of 137Cs was observed using C. reinhardtii with a rate constant of 2.4 Bq min−1 and S. obliquus after 3 h of incubation at pH 7 with rate constant of 2.5 Bq min−1. Chlorella vulgaris was able after 3 h of incubation to remove 241Am and 239Pu up to 90 and 70% in aquatic solutions at pH 1.7 and pH 1.5, with rate constants of 4.4 mBq min−1 and 2.8 × 10−2 mBq min−1, respectively. Novelty statement Ecologically suitable methods for the decontamination of liquid radioactive waste or radioactively contaminated areas are becoming more and more important due to the pollution of the planet. We believe that phytoremediation of radionuclides using microalgae is one of the optimal ecological methods to decontamination of radioactive waste. Microalgae as unicellular organisms have a number of advantages over the other organisms used in bioremediation—high level of tolerance to the environment, fast growth rates, high tolerance to various pH levels, etc. In this study, we used 3 different strains of microalgae for phytoremediation of various radionuclides (137Cs, 60Co, 241Am, and 239Pu). This research was focused on ex situ phytoremediation of radionuclides using microalgae at various pH levels of radioactively contaminated solutions. Due to the ability of microalgae to adapt to sometimes even extreme pH values, this research may be interesting for many institutions and researchers dealing with more environmentally friendly methods of decontamination of radioactive waste.

Biosynthesis of Silver Nanoparticles from Synechocystis sp to be Used as a Flocculant Agent with Different Microalgae Strains

Background: Biofuels produced from trans-esterification of high lipid content in microalgae represent a promising alternative renewable source of energy to the limited and depleted global fossil fuel reservoir. The most critical step in such a process is the harvesting of algal cells. Objective: We aimed to improve the current methodology for microalgae harvesting via utilizing biosynthesized silver nanoparticles (AgNPs) from Synechocystis sp. ElfSCS31 as an eco-friendly, stable, and affordable flocculant agent. Methods: AgNPs were prepared by the green synthesis method using the alcoholic extract of Synechocystis sp. ElfSCS31. The synthesized nanoparticles were characterized by Zeta sizer, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and UV-Vis Spectroscopy. Biosynthesised AgNPs were applied for harvesting 20 microalgae strains, and then, harvesting efficiency was determined by UV Spectrophotometry. Results: Our results revealed an average size of polydispersed nanoparticles ranging from 10 to 100 nm for prepared AgNPs and the potential of 1.78 mV, with an average crystallite size of 22 nm. Biosynthesised AgNPs exhibited harvesting efficiency towards different strains of microalgae, which reached 97% in some strains as in Chlorella lobophora and Chlorococcum oleofaciens. Conclusion: The presented study introduces a feasible strategy using biosynthesized AgNPs as a flocculant agent to harvest different strains of microalgae at normal growth conditions of light and temperature. Our developed method could replace the classical high-cost step of harvesting that leads to unravelling the full potential of microalgae as a promising and fascinating source for biofuels production.

Toxicity of Cadmium (Cd) on microalgal growth, (IC50 value) and its exertions in biofuel production

This study evaluated the IC50 value of cadmium against four different strains of microalgae. Chlorella sorokiniana was able to tolerate 300 mg/L of cadmium. The lipid productivity increased by 6% at 50 mg/l of Cd (II) stress. The decrease in biomass productivity was recorded with increasing concentration of Cd. The results showed that chlorophyll contents, chlorophyll a (Chl a) and chlorophyll b (Chl b) gradually decreased on increasing the concentration of Cd over 100 mg/l. The FAME composition of C. sorokiniana cultivated under Cd (II) stress and control medium were analyzed to determine the quality of the biodiesel produced. The major fatty acids present in the TAGs of the treated microalga were C10:0, C12:0, and C15:0.

Wastewater treatment by microalgae-bacteria co-culture system

Aim: Microalgae is one of the bioremediation agents in wastewater treatment due to its ability to degrade nutrients and organic compounds. Several studies reported that co-cultivation of microalgae and bacteria, i.e. Microalgae Growth Promoting Bacteria (MGPB) could improve the nutrients removal process. This MGPB helps to degrade complex nutrient compounds into smaller components before being taken up by microalgae. The objective of this study is to investigate the effectiveness of co-cultured (microalgae and bacteria) system compared to axenic microalgae system in the removal of major nutrients (ammonium and phosphorus) and chemical oxygen demand (COD) in synthetic wastewater. Methodology and result: In this study, two different strains of microalgae (Chlorella vulgaris and Scenedesmus quadricauda) were each co-cultured with a MGPB (Azospirillum brasilense) and their effectiveness in the removal of major nutrients and COD were compared. The results show that, the nutrients and COD removal were higher in cocultured system compared to the axenic microalgae under similar cultivation conditions for both microalgae strains. Higher percentage removal was obtained from co-cultured C. vulgaris compared to that from co-cultured S. quadricauda which were 86% and 48%, 44% and 31%, 62% and 35% for ammonium, phosphorus and COD removal respectively. Conclusion, significance and impact of study: The findings of this study demonstrate the potential of the co-culture of C. vulgaris and A. brasilense to be applied in wastewater treatment, specifically replacing the aerobic digestion process in secondary stage of conventional wastewater treatment. This study provides an important insight into developing an efficient and environmental friendly method to treat wastewater by incorporating the green technology in the treatment system.

Effect of light spectrum on isolation of microalgae from urban wastewater and growth characteristics of subsequent cultivation of the isolated species

Light quality plays an important role in regulation of microalgae growth. The aim of this work was to investigate the role of light spectrum in isolation of different strains of microalgae from urban wastewater. Screening and isolation under three light spectrums of white, red, and blue resulted in three different strains of Chlorella sorokiniana IG-W-96, Chlorella vulgaris IG-R-96, and Chlorella sp. IG-B-96, respectively. The strains were identified and named based on morphological characterization under light and confocal microscopy followed by molecular characterization. It was revealed that the light spectrum had significant influence on microalgae cell size. The largest and smallest cells were observed under blue and red light, respectively. The isolated strain under blue light when subsequently cultured under blue light in suspension mode showed the highest biomass density of 1.21±0.00gl−1, as well as lipid density and productivity of 0.29±0.02gl−1 and 40.24±4.02mglipidl−1day−1, respectively. Due to its shorter growth time, however, maximum biomass productivity was obtained for the isolated and cultured strain under red lights. The proposed illumination methodology in isolation and cultivation improved growth characteristics, in such a way that similar light spectra in both steps led to the highest amounts of biomass, lipid, and productivities for each strain.

Isolation and identification of indigenous marine diatoms (Bacillariophyta) for biomass production in open raceway ponds

For the successful, large-scale cultivation of microalgae, which for our work refers to diatoms, it is important to select the appropriate species for the right environment. Intensive research on the growth of different strains of microalgae from several regions worldwide is an ongoing effort. The aim of our research in this context was to select the best isolates of diatoms from different coastal sites in Oman, a region whose flora is poorly known, and identify these species using molecular (nuclear-encoded small subunit ribosomal RNA and chloroplast-encoded rbcL and psbC) and morphologic data. We aimed also to investigate and measure the growth rate, biomass production and fatty acid composition under ambient environmental conditions. Our results showed that in contrast to most of the research reported in the literature, the production of biomass from six isolates has been successfully carried out with reduced amounts of nutrients and without CO2 addition. Growth rates for species cultivated outdoors were high and ranged from 0.37 to 0.92 day−1. These findings are economically very promising as fast growth rates, associated with reduced operational costs, could remarkably improve the production efficiency and thereby justify their use as biomass feedstocks. Molecular data revealed that one isolate was Bellerochea malleus, four isolates represented an unidentified species of Bellerochea and the remaining strain studied represented an unidentified species of the genus Nitzschia. These six strains were rich in polyunsaturated fatty acids, with an average of 47% of the total fatty acids, confirming their potential use as aquaculture feed supplements.

Biodiesel from microalgae: The use of multi-criteria decision analysis for strain selection

Microalgae strain selection is a vital step in the production of biodiesel from microalgae. In this study, Multi-Criteria Decision Analysis (MCDA) methodologies are adopted to resolve this problem. The aim of this study is to identify the best microalgae strain for viable biodiesel production. The microalgae strains considered here are Heynigia sp., Scenedesmus sp., Niracticinium sp., Chlorella vulgaris, Chlorella sorokiniana and Auxenochlorella protothecoides. The five MCDA methods used to evaluate different strains of microalgae are Analytic Hierarchy Process (AHP), Weighted Sum Method (WSM), Weighted Product Method (WPM), Discrete Compromise Programming (DCP) and Technique for the Order of Preference to the Ideal Solution (TOPSIS). Pairwise comparison matrices are used to determine the weights of the evaluation criteria and it is observed that the most important evaluation criteria are lipid content and growth rate. From the results, Scenedesmus sp. is selected as the best microalgae strain among the six alternatives due to its high lipid content and relatively fast growth rate. The AHP is the most comprehensive of the five MCDA methods because it considers the importance of each criterion and inconsistencies in the rankings are verified. The implementation of the MCDA methods and the results from this study provide an idea of how MCDA can be applied in microalgae strain selection.

Evaluation of wavelength selective photovoltaic panels on microalgae growth and photosynthetic efficiency

Abstract Large-scale cultivation of microalgal biomass in open systems can benefit from the low cost of using natural sunlight, as opposed to artificial light, but may encounter problems with photoinhibition, high evaporation rates, potential contamination and high energy demand. Wavelength selective luminescent solar concentrator (LSC) panels can solve some of these problems when incorporated into low-cost sheltered structures for algal biomass production that concurrently produce their own electricity by harnessing select portions of solar energy, not used for algal growth. The LSC panels in this study contained a fluorescent dye, Lumogen Red 305, which transmits blue and red wavelengths used for photosynthesis with high efficiency, while absorbing the green wavelengths and re-emitting them as red wavelengths. The fluorescently generated red wavelengths are either transmitted to boost algal growth, or waveguided and captured by photovoltaic cells to be converted into electricity. We found that different strains of microalgae (currently used commercially) grew equally well under the altered spectral conditions created by the luminescent panels, compared to growth under the full solar spectrum. Thus this technology presents a new approach wherein algae can be grown under protected, controlled conditions, while the cost of operations is offset by the structure's internal electrical production, without any loss to algal growth rate or achievable biomass density.

Biosorption of trace metals from aqueous multimetal solutions by green microalgae

Two strains of green microalgae C. reinhardti and C. pyrenoidosa were examined for their biosorption of Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ from aqueous multi-metal solutions. A wide range of biosorption capacities can be observed due to different strains of microalgae and different species of trace metals. This characteristic was ascribed to the distinct components and structures of algal cell walls and the different physicochemical properties of trace metals, such as atomic weight and ion density. C. pyrenoidosa showed higher uptake capacities than C. reinhardti and both of them had a preference for the uptake of cadmium over others in the trace metal solution, suggesting they can be a good biomaterial for biosorption of cadmium. Live microalgal cells displayed a more complex sorption process than dead microalgal cells because of cell assimilation.

Selection of Microalgae and Cyanobacteria Strains for Bicarbonate-Based Integrated Carbon Capture and Algae Production System

Using microalgae to capture CO2 from flue gas is an ideal way to reduce CO2 emission, but this is challenged by the high cost of carbon capture and transportation. To address this problem, a bicarbonate-based integrated carbon capture and algae production system (BICCAPS) has been proposed, in which bicarbonate is used for algae culture, and the regenerated carbonate from this process can be used to capture more CO2. High-concentration bicarbonate is obligate for the BICCAPS. Thus, different strains of microalgae and cyanobacteria were tested in this study for their capability to grow in high-concentration NaHCO3. The highest NaHCO3 concentrations they are tolerant to were determined as 0.30 M for Synechocystis sp. PCC6803, 0.60 M for Cyanothece sp., 0.10 M for Chlorella sorokiniana, 0.60 M for Dunaliella salina, and 0.30 M for Dunaliella viridis and Dunaliella primolecta. In further study, biomass production from culture of D. primolecta in an Erlenmeyer flask with either 0.30 M NaHCO3 or 2 % CO2 bubbling was compared, and no significant difference was detected. This indicates BICCAPS can reach the same biomass productivity as regular CO2 bubbling culture, and it is promising for future application.

Fatty acids as biomarkers of microalgae

Microalgae are primary producers of the food chain and hold prominence towards pharmaceutical and nutraceutical applications. Fatty acids (FAs) are one of the primary metabolites of microalgae, which enrich their utility both in the form of food and fuels. Additionally, the vast structural diversity coupled with taxonomic specificity makes these FAs as potential biomarkers. The determination of lipid and fatty acid profiling of 12 different strains of microalgae has been accomplished in this study and further discussed in respect to their chemotaxonomic perspective in microalgae. Palmitic acid (C16:0) and oleic acid (C18:1n9c) were found to be dominant among the members of Cyanophyceae whereas members of Chlorophyceae were rich in palmitic acid (C16:0), oleic acid (C18:1n9c) and linoleic acid (C18:2n6). The application of principal component analysis (PCA) and algorithmic hierarchical clustering (AHC) resulted in the segregation of the studied microalgal strains into 8 different orders belonging to 2 distinct phyla according to their phylogenetic classification. Nutritionally important FAs like eicosapentaenoic acid (EPA, C20:5n3) and docosahexaenoic acid (DHA, C22:6n3) were detected only in Chlorella sp. belonging to Chlorophyceaen family. Differential segregation of microalgae with respect to their fatty acid profile indicated the potential utility of FAs as biomarkers.

Improvement of lipid production in the marine strains Alexandrium minutum and Heterosigma akashiwo by utilizing abiotic parameters

Two different strains of microalgae, one raphidophyte and one dinoflagellate, were tested under different abiotic conditions with the goal of enhancing lipid production. Whereas aeration was crucial for biomass production, nitrogen deficiency and temperature were found to be the main abiotic parameters inducing the high-level cellular accumulation of neutral lipids. Net neutral lipid production and especially triacylglycerol (TAG) per cell were higher in microalgae (>200% in Alexandrium minutum, and 30% in Heterosigma akashiwo) under treatment conditions (25°C; 330 μM NaNO(3)) than under control conditions (20°C; 880 μM NaNO(3)). For both algal species, oil production (free fatty acids plus TAG fraction) was also higher under treatment conditions (57 mg L(-1) in A. minutum and 323 mg L(-1) in H. akashiwo). Despite the increased production and accumulation of lipids in microalgae, the different conditions did not significantly change the fatty acids profiles of the species analyzed. These profiles consisted of saturated fatty acids (SAFA) and polyunsaturated fatty acids (PUFA) in significant proportions. However, during the stationary phase, the concentrations per cell of some PUFAs, especially arachidonic acid (C20:4n6), were higher in treated than in control algae. These results suggest that the adjustment of abiotic parameters is a suitable and one of the cheapest alternatives to obtain sufficient quantities of microalgal biomass, with high oil content and minimal changes in the fatty acid profile of the strains under consideration.

Isolation and application of SO X and NO X resistant microalgae in biofixation of CO 2 from thermoelectricity plants

Microalgae have been studied for their potential use in foodstuffs, agriculture, in the treatment of wastewater and, in particular, in the reduction of atmospheric carbon dioxide, the main cause of global warming. Thermoelectricity plants account for 22% of CO 2 emitted into the atmosphere and native microalgae may be more tolerant to the gases emitted from burning fossil fuels. In the study presented here, microalgae were isolated from ponds next to a Thermoelectricity Plant, located in southern Brazil, and identified as Synechococcus nidulans and Chlorella vulgaris. The isolated microalgae were grown and compared with two different strains of microalgae, Spirulina sp. and Scenedesmus obliquus, for CO 2 biofixation. The microalgae were exposed to 12% CO 2, 60 ppm of SO 2 and 100 ppm of NO, simulating a gas from coal combustion. The C. vulgaris had similar behavior to Spirulina sp., with 13.43% of maximum daily fixation. The microalgae with the greater fixing capacity were C. vulgaris and Spirulina sp. and these can be grown in electric power plants for CO 2 biofixation of the coal combustion gas, which would help reduce global warming.

Biotransformation of AD and ADD using Nostoc muscorum

The potential of microalgae for steroid transformation has been studied less than other microorganisms. They have been applied for the years in the treatment of environmental pollutions and preparation of nutrients. At the first time, Abul-Hajj and Qian indicated the conversion of androstendione (AD) to testosterone with eleven different strains of microalgae. Previtera’s group showed the transformations of progesterone and prednisolone in several microalgal cultures within four studies. In other investigations, steroid substrates were 5?-androstane-3, 17-dione, adrenosterone, androsta-1, 4-diene-3, 17-dione (ADD) and 17?-hydoxy-17?-methylandrosta-1, 4-dien-3-one. Hydrocortisone biotransformation using Nostoc muscorum was also reported with Tabatabie group. In this study, the ability of Nostoc muscorum, blue green algae, for biotransformation of AD and ADD were investigated. This potential has not been previously examined. The selected microalgae was isolated during a screening program from soil samples collected from paddy field of north of Iran. The fermentation media were included BG-11 medium together with AD or ADD 0.05%, separately, as steroid substrates. The experiment was illuminated continuously with fluorescent lamps at 40 µEm-2S-1, and incubated at a temperature of 25±2°C without shaking for ten days. The chloroform extract was loaded on silica gel plates with acetone/hexan (1:1) solvent system. The obtained fractions were further purified by re-chromatography, followed by crystallization. Then, the metabolites and unconverted substrates from each experiment were identified by melting points and spectral methods including 13C NMR, 1H NMR, FTIR and MS. The fermentation reaction of AD with Nostoc muscorum led to accumulation of testosterone in the broth medium. 1-Dehydrotestosterone was the product of ADD bioconversion in the microalgal culture. In both cases, the bioconversion characteristics observed were 17-carbonyl reduction. Thus, the microorganism represented to act selectively at the ketone group on the D-ring of both androstane like steroids.