Monoraphidium Contortum Research Articles

Enhancing methane yield from microalgae: abiotic stress and cells disruption with quartz powder

This study investigates the biochemical methane potential (BMP) of microalgal biomass, introducing a novel cells disruption method using quartz powder (SiO2). A two-phase algae cultivation, involving nitrogen deprivation and salinity shifts, was employed to biochemically modify the biomass of two brackish green algae strains, Chlorella vulgaris and Monoraphidium contortum, enhancing their methane (CH4) production potential. Mechanical disruption of the algal cells further increased BMP, with C. vulgaris yielding 305 mL CH4/g volatile solids (VS) and M. contortum reaching 324 mL CH4/g VS, reflecting respective increases of 51 % and 86 %. The integration of this efficient mechanical cell disruption method with a simple, stress-based cultivation strategy presents significant potential for enhancing the methane yield of microalgal biomass.

Exploring freshwater microalgal strains for Omega-3 polyunsaturated fatty acids and carotenoids from the Ganges River in India

Microalgae, increasingly recognized as a cost-effective reservoir of natural compounds. Their extensive application in nutraceuticals, and pharmaceuticals industry are making them mercantile worthy. This study delves into the realm of bioprospecting freshwater microalgae with focus on extracting high-value products, specifically omega-3 polyunsaturated fatty acids and carotenoids. Freshwater-derived microalgal strains were isolated from Ganges River and refined, and grown in BG-11 culture medium. Microscopic examination was used to screen these microalgae based on morphology. Subsequently, the biochemical properties of the selected microalgal strains were investigated. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two crucial omega-3 polyunsaturated fatty acids, were identified in significant quantities in Chlorella variabilis (3.6±1.32%; 2.7±0.13%) and Monoraphidium contortum (2.2±0.36%; 3.2±0.2%). Moreover, the investigation also focused on carotenoids; lutein and astaxanthin. The findings indicated a high concentration of lutein in Chlorella variabilis (4.5 mg g−1), while Monoraphidium contortum exhibited abundant levels of astaxanthin (5.9 mg g−1). These research findings demonstrate the promising capacity of the isolated microalgal strains to yield valuable bioactive compounds.

Effectiveness of point-of-use (POU) filter system for removal of contaminants from water

Groundwater supplies most of the drinking water in the small settlements in the Danubian plain region of Bulgaria. The region is mostly agricultural, leading to chemical pollution, mostly with nitrogen, of the shallow groundwater. Direct health concerns, linked to nitrates contamination of water, determine the increased popularity of drinking water point-of-use (POU) filtration pitchers. The objective of this study was to evaluate the effectiveness of a commercial pitcher filtration system in removing select pollutants, such as metal ions, namely, copper and iron, nitrate nitrogen, and suspended solids (algal culture of Monoraphidium contortum) from augmented tap water. In addition, we have studied the effects on electrical conductivity and pH of water. The POU system of choice was a widely used brand name in Bulgaria, providing cartridges that fit most of the European pitcher filter brands. We have evaluated the performance of the filters at three different exploitation intervals – pre-washed new filter (0%), 50%, and 100% of the exploitation capacity set according to manufacturers’ claims of recommended volume of water, as well as at different contact times between the water and the filter media. The results indicate that the efficiency of the filters diminishes with aging and increases with increasing contact time – multiple filtrations.The efficiency in terms of electrical conductivity and amount of iron decreases proportionally with filter age, and in terms of phosphates, the maximum effect is observed in filters at 50% capacity. Water filtration reduced water conductivity by 12% in a single filtration and stabilized the pH values towards the neutral range. The effect on pH values is inversely proportional to the buffering capacity of the water. The filters removed 85–98% of copper ions and 20% of iron ions. Nitrate removal efficiency averages 40% and doubling the contact time increases the efficiency to 70%. The efficiency of removing suspended solids is on average 17%, mainly due to the small size of the particles.Overall, the POU systems are an effective way to purify water at home. The filter cartridges effectively reduce contaminants, such as metals and nitrates, which are particularly problematic in areas supplied by groundwater sources.

Evaluation of Monoraphidium contortum for the tertiary treatment of dairy industry wastewater and biomass production with nitrogen supplementation

The present study sought to evaluate the secondary wastewater from dairy industry as a culture medium for Monoraphidium contortum, in bench-scale tubular photobioreactor, aiming at tertiary wastewater treatment and microalgae biomass production. Since the used secondary wastewater contained residual phosphorus (P) but negligible residual nitrogen (N), we also evaluated the nitrogen supplementation, following Redfield ratio (N:P = 16:1) and the same N:P proportion of Bold Medium (N:P = 1.71:1). These cultures were compared to secondary wastewater without N and Bold Medium (control). Secondary wastewater without N addition provided lower values of maximum biomass concentration, indicating the importance of this supplementation. The nitrogen supplementation following Bold Medium represented the best protocol, since biomass productivity was higher than that in control culture, but with lower nitrogen addition (in comparison with the supplementation following Redfield proportion). The biomass of M. contortum showed to be an excellent candidate for oil production, which could be employed as feedstock for biodiesel, for example.

The Effect of Brachionus calyciflorus (Rotifera) on Larviculture and Fatty Acid Composition of Pikeperch (Sander lucioperca (L.)) Cultured under Pseudo-Green Water Conditions

A new cultivation system with the chlorophyte Monoraphidium contortum combined with a self-sustaining culture of the freshwater rotifer Brachionus calyciflorus was applied for Sander lucioperca (L.) larviculture. Survival, morphometrics, as well as fatty acid composition of pikeperch larvae were analyzed after a ten-day feeding period. By using the pseudo-green water technique with improved aeration and water movement at the surface, survival rates reached up to 94%, with a total larval length of 8.1 ± 0.3 mm and a specific length growth rate of up to 4.1% day−1 for S. lucioperca. The biochemical composition of B. calyciflorus and especially its contents in C18 PUFAs and suitable n-3/n-6 ratios met the nutritional requirements of pikeperch larvae. The high abundance of highly unsaturated fatty acids (HUFAs) in the diet appeared to be less important in the first feeding due to a possible retention of essential fatty acids, which originate from the yolk sac reserves, at adequate levels. Exponential growth of microalgae and zooplankton under the applied conditions was most effective when stocking M. contortum five days and B. calyciflorus three days before adding the fish larvae. Appropriate timing and sufficient live feed density allowed a successful integration of B. calyciflorus into pikeperch larviculture. We hypothesize that feeding pikeperch larvae with a self-sustaining Brachionus-culture under pseudo-green water conditions with minor disruptions during larviculture will improve survival and growth. This system is a first step towards pikeperch larviculture inside recirculated aquaculture systems (RAS) under continuous feed supply with live feed within the same aquaculture unit.

The Fouling Effect on Commercial Ceramic Membranes during Filtration of Microalgae Chlorella vulgaris and Monoraphidium contortum

Although interest in the use of membranes for the concentration of microalgal biomass has steadily been growing, little is known regarding the phenomena of membrane fouling. In addition, more attention has been given to polymeric membranes compared to ceramic membranes, which have a longer life that is associated with a higher resistance to aggressive chemical cleaning. In this study, microfiltration (MF) and ultrafiltration (UF) of two microalgae species, Chlorella vulgaris and Monoraphidium contortum, were carried out using tubular crossflow ceramic membranes. Permeate flux was measured, resistance was calculated, and dissolved organic carbon (DOC) was determined. The flux reduction during the first 10 min of filtration was higher for MF than UF (>70% and <50%), and steady-state permeate fluxes were <5% (for MF) and <25% (for UF) of initial (in m3 m−2 s−1) 6.2 × 10−4 (for MF) and 1.7 × 10−4 (for UF). Total resistances (in m−1) were in the ranges of 4.2–5.4 × 1012 (UF) and 2.6–3.1 × 1012 (MF) for M. contortum and C. vulgaris, respectively. DOC reduction was higher for UF membrane (>80%) than for MF (<66%) and DOC concentrations (mg C L−1) in permeates following MF and UF were about five and two, respectively. In conclusion, we demonstrated: (i) higher irreversible resistance for UF and reversible resistance for MF; (ii) permeate flux higher for UF and for M. contortum; (iii) the significant role of dissolved organic compounds in the formation of reversible resistance for MF and irreversible resistance for UF.

Response to nutrient variation on lipid productivity in green microalgae captured using second derivative FTIR and Raman spectroscopy

Two green microalgae species Monoraphidium contortum (M. contortum) and Chlamydomonas sp. that were identified to accumulate lipids were subjected to four different nutrient treatments (NP1-NP4), ranging in nitrate (0.05–5 mM N) and phosphate (2.8–264 μM P) concentrations, at a fixed N:P ratio of ∼18. The effect of nutrient variation on lipid productivity in the species was investigated using second derivative (SD) FTIR and Raman spectroscopy of algal biomass. SD spectral analysis revealed high production of lipid in the form of hydrocarbons (CH) (3000–2800 cm−1), triacylglycerides (TAGs)(∼1740 cm−1), saturated (SFA)(∼1440 cm−1), and unsaturated fatty acids (UFA)(∼3010 cm−1) for the nutrient deplete condition (NP1) in both species. Changes in signals attributed to lipids in proportion to other biochemical components were consistent with physiological changes expected from nutrient depletion. Relative signal intensities for lipids showed a significant increase in NP1, in particular, CH, TAGs in relation to protein signals (in SD-FTIR), and SFA, UFA in relation to carotenoid signals (in SD-Raman). PCA performed on the negative spectral values of the SD-FTIR and SD-Raman data for the four NP treatments enabled discrimination not only between the species but also between the NP treatments and the timing of harvest. M. contortum was found to contain a relatively higher proportion of CH, TAGs, SFA, and UFA compared to Chlamydomonas sp. Peak areas from the negative SD spectra, informed by PCA analysis, enabled capturing quantifiable changes in a manner that is consistent with known microalgal physiology. SD-FTIR and SD-Raman spectroscopy have been shown to possess superior potential to capture relevant microalgal physiological changes.

Statistical study of growth kinetics and lipid content of microalgae grown in brackish waters for bioenergetic purposes

This study aimed to statistically prove the influence of salinity on growth kinetics and intracellular lipid accumulation in microalgae. The species Chlorella sp., Scenedesmus acuminatus, Nannochloropsis sp., Monoraphidium contortum and Pediastrum tetras were studied, which were isolated in the Brazilian semi-arid region and cultivated in synthetic media with the addition of NaCl. From the crops, growth kinetics, dry biomass production and lipid content were analyzed, using the experimental planning for one factor as a tool, with the NaCl concentration as an independent variable. The kinetic parameters maximum growth speed (µmax) and generation time (tg), as well as lipid concentration were the response variables studied. The results showed that, in the species Scenedesmus acuminatus, Nannochloropsis sp. and Pediastrum tetras, salt stress contributed to the increase in µmax and the consequent decrease in tg. The highest levels of lipid accumulation were obtained in Nannochloropsis sp. (62.04%), in the medium with the highest salinity and Pediastrum tetras (54.04%) in the lowest. Dry biomass production was higher in Scenedesmus acuminatus (1,941.37 mg.L-1) and Nannochloropsis sp. (1237.05 mg.L-1), both at a concentration of 4.0 g.L-1. Therefore, saline stress acted directly on the cell growth and lipid content of the species, which can be used as a device to enhance lipid production for the purpose of producing biofuels.

Evaluation of natural flocculant efficiency in the harvest of microalgae Monoraphidium contortum

This study assesses two parameters that can result in high efficiency in the recovery of the microalgae Monoraphidium contortum. The significant contribution of this paper is to test different coagulants in different conditions of concentration in the coagulation and flocculation processes followed by sedimentation to evidence the best coagulant and the best condition for harvesting of Monoraphidium contortum biomass. So the proposed methodology aimed to perform preliminary tests using a tannin-based cationic coagulant (TANFLOC SG®), FeCl2, and Al2 (SO4)3, where they were performed at concentrations of 0, 20, 40, 60, 80, and 100 mg L−1 at a fast mixing speed of 400 RPM. The tests determined 20 mg L−1 of Tanfloc SG® as the most efficient turbidity reduction in the preliminary test. The obtained results were used to construct a non-factorial central composite planning. Therefore, after a design of experiments, the study outcome shows the best turbidity removal range from the main tests came at 35 mg L−1 and 550 RPM of fast mixing speed.

Evaluation of green microalgae isolated from central and north coast of Sao Paulo as source of oil

Microalgae strains, newly isolated from freshwater in mangrove areas of Central and North Coasts of Sao Paulo State (Brazil), were evaluated regarding total protein and lipid content, and fatty acids profile. The biochemical composition was compared with that observed in strains obtained by UTEX Culture Collection (USA). Among seven identified green algae, Monoraphidium contortum (CCMA-UFSCar-701) presented the highest lipid content (43.60%), close to that observed in Botryococcus braunii (UTEX-2441; 48.85%). Protein content in isolated strains varied in the range of 13.90~23.60%. Finally, the most abundant fatty acids were palmitic acid (C16:0), oleic acid (C18:1), linoleic acid (C18:2), and y-linolenic acid (C18:3).Chlorella vulgaris (CCMA- UFSCar-704) may be highlighted for its high linoleic acid content (49%). On the other hand, Elakatothrix sp (CCMA- UFSCar-702) and Scenedesmus obliquus (UTEX-B2630) presented the highest content of oleic acid (41% and 43%, respectively), which is preferable for oils to be used as feedstock for biodiesel.

The Community of Chlorophyta as Bioindicator of Water Pollution in Pandanduri Dam District of Terara East Lombok

The Pandanduri Dam has a function as a support for agricultural irrigation water and also supports community activities so that it will affect the quality of its waters. The quality of the water needs to be analyzed because it can affect the aquatic ecosystem. This study aims to determine the level of water pollution in the Pandanduri Dam based on the phytoplankton community from the Chlorophyta Division. This type of research is descriptive exploratory. Sampling was carried out at 5 stations that were haphazardly selected with ecological representativeness consideration. Phytoplankton data were analyzed using the abundance formula, Shannon-Wiener diversity index, PIELOU uniformity index, and Simpson dominance index. The phytoplankton from the Chlorophyta Division found in the Pandanduri Dam were 14 species that are Pediastrum duplex var. Gracillimum, Gonium sp. 1, Gonium sp. 2, Coelastrum reticulatum, Scenedesmus acuminatus, Cosmarium sp., Chlamydomonas nasuta, Chlamydomonas sp., Selenastrum capricornutum, Monoraphidium dybowskii, Monoraphidium contortum, Monoraphidium irregular, Westella botryoides, and Kirchneriella lunaris consisting of 4 orders (Sphaeropleales, Chlorococcales, Chlamydomonadales and Desmidiales) and 10 genera (Pediastrum, Coelastrum, Scenedesmus, Gonium, Cosmarium, Chlamydomonas, Selenastrum, Monoraphidium, Westella, and Kirchneriella). The species diversity index of 2.21 is classified as moderate diversity, the species uniformity index is 0.83 which indicates even species growth, and the species dominance index indicates that no species dominates with a value of 0.12. The level of water pollution in the Pandanduri Dam was found in the moderate pollution category (oligotrophic).

Algal flora Saint-Petersburg water bodies

In the spring and summer of 2019, 43 lakes and ponds of Saint Petersburg were surveyed. The algal flora contains 110 species of algae of the following divisions: Cyanophyta =Cyanobacteria=Cyanoprokaryota – 18, Cryptophyta – 1, Dinophyta – 9, Euglenophyta – 11, Chlorophyta – 57 Streptophyta - 2, Ochrophyta (classes Chrysophyceae – 2, Bacillariophyceae – 10). For the majority of the found species, the saprobity mark and saprobic index were specified. The most diverse group in the water bodies of Saint Petersburg is green algae, which includes single and coenobial algae of the coccoid and monad tallom organization, which are well adapted to vegetation in the water column. In most reservoirs at spring Monoraphidium arcuatum (Korshikov) Hindák and Monoraphidium contortum (Thuret) Komárkova-Legnerova, species of genera Scenedesmus, including species of the genera Desmodesmus and Tetradesmus actively vegetate. In the reservoirs of Saint Petersburg, the leading positions are taken by euglenic algae, especially species of genera Trachelomonas (Trachelomonas hispida (Perty) F. Stein, Trachelomonas volvocina (Ehrenberg) Ehrenberg). Summer phytoplankton differs in the more vigorous development of blue-green algae-especially such species as Dolichospermum flosaquae (Brébisson ex Bornet & Flahault) P. Wacklin, L. Hoffmann & Komárek, Dolichospermum spiroides (Klebhan) Wacklin, L. Hoffmann & Komárek. The species of β- mesosaprobic dominate. There are also α-mesosaprobes and species with a wide range of existence in reservoirs with different degrees of organic content. Biological analysis of the surveyed water bodies shows that their condition is satisfactory.

Exploiting the use of agro-industrial residues from fruit and vegetables as alternative microalgae culture medium

There is a need for searching new microalgae species, and the most suitable strategy to increase the cost-effectiveness of a microalgae culture system is to use resources of low costs, such as residues. This study aimed to evaluate the cultivation of microalgae isolated from the Brazilian Northeast region (Lagerheimia longiseta, Monoraphidium contortum, and Scenedesmus quadricauda) in an alternative medium of low cost (biocompost of discarded fruits and vegetables) with a view to possible applications in the food industry. Microalgae cultivated in the conventional synthetic medium was used as control. The cultivation of microalgae in the alternative medium allowed suitable cell growth, and improved the antioxidant activity and the levels of monounsaturated fatty acid and polyunsaturated fatty acid compared to the synthetic medium. The cultivation of S. quadricauda and L. longiseta species in the alternative medium resulted in increased protein content and/or total phenolic content, and improved health indices (lower levels of atherogenic, thrombogenic, and hypercholesterolemic saturated fatty acids indices, and higher levels of desired fatty acids index) compared to cultivation in synthetic medium. The cultivation of M. contortum in the alternative medium contributed to the production of higher lipid content, mainly saturated fatty acid (palmitic acid), which contributed negatively to the health indices. This study proved that S. quadricauda and L. longiseta microalga species from freshwaters have significant potential for distinct applications in functional food industries, and the biocompost of discarded fruits and vegetables is a suitable medium for microalgae cultivation.

Carbon dioxide capture with microalgae species in continuous gas-supplied closed cultivation systems

This study has presented the assessment of carbon dioxide bioremediation rate, growth kinetics, and protein content of the Scenedesmus obliquus, Monoraphidium contortum, Psammothidium sp, and Chlorella vulgaris species, which are supplying with 0.04 % and 10 % carbon dioxide concentration in the different types of photobioreactor (glass flask and tubular vertical column). This experiment showed the growth parameters for all of the microalgae species significantly increased when fed 10 % carbon dioxide compared to those fed 0.04 % carbon dioxide in either type of PBR. Maximum growth kinetics were observed in Chlorella vulgaris when it was grown in 10 % CO2 in the tubular vertical column PBR with 2.12 g L−1 (Xmax), 0.61 g L−1 d−1 (Pmax), 11.07 g d−1 (RC), 51.59 % (wt.%), and 42.75 % (Overall CR%). In addition, we observed a maximum protein content at Chlorella vulgaris (72.12 %) by cultivation in glass flask PBR with 10 % CO2.

Growth, calcium content, proximate composition, and fatty acid composition of triangle sail mussel (Hyriopsis cumingii) fed five different microalgal diets

Sustainable cultivation of triangle sail mussel Hyriopsis cumingii lacks a suitable, optimal diet. To determine the optimum microalgal diet H. cumingii, we tested five microalgal diets (Cyclotella sp., Chlorella pyrenoidosa, Scenedesmus dimorphus, Monoraphidium contortum, and a mix of these four microalgae) using single factor experiments. We measured body growth, pearl growth, proximate composition, fatty acid composition, and calcium (Ca) content in the mantle and foot of H. cumingii. Overall, diet had significant effects on the growth of H. cumingii (P < .05), and the group fed Cyclotella sp. showed the greatest (P < .05) increases in weight, shell length, height, and width, and pearl weight. The Ca content of the mantle and foot also differed significantly between treatments (P < .05); the highest content in the foot was observed in mussels fed Cyclotella sp., while the highest content in the mantle was found in mussels fed S. dimorphus and M. contortum. The crude protein contents of the foot and mantle were highest in mussels fed Cyclotella sp., and both were positively correlated with growth; the moisture content of the foot was negatively correlated with growth. The mussels fed the mixed microalgae had the highest polyunsaturated fatty acids (PUFAs) proportion (P < .05), while the group fed Cyclotella sp. showed the lowest PUFAs and the highest saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) proportions (P < .05). The proportions of SFAs and MUFAs were positively correlated with growth, and the proportion of PUFAs was negatively correlated with growth. Principal component analysis showed that the fatty acid composition differed among diet groups. In summary, mussels showed different growth, Ca content, and proximate and fatty acid compositions when fed different microalgal diets. Cyclotella sp. was the optimum microalgal diet, followed by S. dimorphus. Based on growth rate and tissue compositions of H. cumingii obtained here, a suitable diet for this species should include these microalgae.

Comparative analysis of free-living and particle-associated bacterial communities of Lake Baikal during the ice-covered period

Free-living (FLC) and particle-associated (PAC) bacterial communities contribute differentially to the cycling of matter in the environment. In this work we have for the first time studied the taxonomic composition and diversity of FLC and PAC in the oligotrophic freshwater Lake Baikal during the under-ice plankton peak. The communities on the bottom ice surface and in the water column under the ice were studied. Analysis by light microscopy showed that the bottom surface of the ice was dominated by green algae Chlorella spp. A complex of microalgae developed in the water column: green algae Monoraphidium griffithii, Monoraphidium contortum, Chlorella spp., chrysophyte Dinobryon cylindricum, haptophyte Chrysochromulina parva, and diatom Synedra acus. Algal abundance on the ice sub-surface was several orders of magnitude higher than that in the water column. According to pyrosequencing data of the bacterial 16S rRNA V3-V4 region, diversity of FLC (as measured by Shannon, Simpson, Chao1 and ACE indices) was higher than that of PAC. Proteobacteria (Burkholderiaceae) dominated the FLC associated with ice; FLC of the water column under ice were dominated by Actinobacteria (Sporichthyaceae and Ilumatobacteraceae) and Verrucomicrobia (Methylacidiphilaceae). PAC associated with ice were dominated by Bacteroidetes (Flavobacteriaceae), while water column-associated PAC were dominated by Verrucomicrobia (FukuN18_freshwater_group, Methylacidiphilaceae) and cyanobacteria (Cyanobiaceae). The difference between free-living and particle-associated, as well as between water column and ice sub-surface bacterial communities, were explored on operational taxonomic unit (OTU) and phylotype levels.

Phytoplankton of Tiligulsky Liman in conditions of change of salt regime

The article represents the research on influence of a number of hydrochemical parameters on the phytoplankton formation in the Tiligulsky Liman in 2015 and the forecast of possible changes in terms of increasing salinity. In the northern, central, southern and coastal part of the Liman, 65 species of microalgae were found, which were mainly diatoms (44) and dinoflagellates (12 species). The coastal waters were characterized by the highest number of phytoplankton (4.3 million cells·l-1) due to the massive development of green algae. The biomass was almost the same at all regions (1618.2 – 1955.8 mg·m-3), except the southern (358.7 mg·m-3). The salinity varied in the following range: 13‰ – in the coastal part, 24‰ – in the south and north, 25‰ – in the central. In the lower part it was revealed the dominance of dinoflagellates of the genera Prorocentrum, Protoperidinium, Gymnodinium (contribution to biomass up to 82%), on the sea coast – green algae Monoraphidium contortum (Thur.) Komark.-Legn., M. minutum (Nageli) Komark.-Legn. (up to 11% by biomass and 67% by abundance). Flagellates reached a fairly high abundance at different sites (up to 10% by biomass and 15% by abundance). Among the diatoms Skeletonema costatum (Grev.) Cl. developed massively in the southern part of the Liman; Ceratoneis closterium (Ehr.) Reimann et JCLewin and Tabularia fasciculata (Ag.C) DMWilliams et Round – in the coastal part; Chaetoceros socialis – in the central, Navicula sp. – in the northern. Correlation and ordination analysis revealed that salinity is the main factor determining the development of plankton microphytes at the studied sites. Oxygen content, depth and temperature are also important factors in the bottom horizon. The content of nutrients is more significant on the surface horizon. Regarding the salinity, 35 species-indicators of salinity were identified, of which 11% were indifferent (freshwater-brackish-water), 37 – mesogalobes (brackish-water) and 51 polyhalobes (marine). In comparison with the studies of the 1980s and 2000s, it was found that the share of freshwater-brackish-water species has decreased significantly, and freshwater algae were absent. Further increase in salinity will lead to raising of the proportion of eurygaline species, such as diatoms Achnanthes brevipes, Halamphora coffeaeformis, Navicula salinarum, N. pontica, N. cancellata, Nitzschia hybrida, Tabularia fasciculata, Ceratoneis closterium, Cocconeis scutellum. These species can withstand fairly large salinity ranges and are the first who massively develop in salinized water bodies.

Effect of nutrient concentration on growth and saxitoxin production of Raphidiopsis raciborskii (Cyanophyta) interacting with Monoraphidium contortum (Chlorophyceae)

Raphidiopsis raciborskii is the dominant species in several subtropical aquatic ecosystems. This study addressed the influence of nutrient concentration on cyanobacteria growth and saxitoxin synthesis. Therefore, we performed bioassays of interaction between the Chlorophyceae Monoraphidium contortum and R. raciborskii simulating oligotrophic and supereutrophic environments. Experiments were carried out in a climatized room for 15 days in pure cultures of each species (control) and mixed (interaction). The biomass growth (biovolume) and specific growth rates were measured. Saxitoxin was analyzed using the ELISA biochemical method. In the oligotrophic environment, the cell volume of R. raciborskii decreased. This species also showed senescence in interaction with M. contortum. However, there were no statistical differences in the saxitoxin synthesis in both conditions. In the supereutrophic environment, the growth of R. raciborskii and saxitoxin production was similar in both the control and interaction conditions. However, M. contortum growth decreased in interaction with the cyanobacteria. The increase in trophic status from oligo- to supereutrophic contributes to the growth of M. contortum in subtropical aquatic ecosystems, but the decrease in the area/volume ratio of cyanobacteria and the saxitoxin synthesis is an evident survival strategy in oligotrophic environments.

Effect of CO2 on the generation of biomass and lipids by Monoraphidium contortum: A promising microalga for the production of biodiesel

In this work, the effect of different concentrations of CO2 (0.03, 2.5, 5.0, 7.5, and 10%) was evaluated on the generation of biomass, the productivity of lipids, the consumption of nitrate and phosphate, the lipid profile, and the quality of biodiesel obtained by Monoraphidium contortum. The maximum productivity of biomass (529.26 mg·L−1·d−1) and of lipids (37.52 mg·L−1·d−1) was obtained by M. contortum with 7.5% CO2. The lipids were transformed to biodiesel through a transesterification reaction; the major components of biodiesel obtained from M. contortum oil were oleic and palmitic acid. Fuel properties were estimated and found to be within the limits for biodiesel of the American Standard for Testing Materials (ASTM 6751:2006) and the European Union Standards (EN 14214:2008). The results obtained with M. contortum in this study justify its transformation into biodiesel of adequate quality.

Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis.

Fourier transform infrared (FTIR) and Raman spectroscopic techniques were employed to analyze the biomolecular transitions and lipid accumulation in three freshwater green microalgal species, Monoraphidium contortum (M. contortum), Pseudomuriella sp. and Chlamydomonas sp. during various phases of their growth. Biomolecular transitions and lipid [hydrocarbons, triacylglycerides (TAGs)] accumulation within the microalgal cells were identified using second derivatives of the FTIR absorption spectroscopy. Second derivative analysis normalized and resolved the original spectra and led to the identification of smaller, overlapping bands. Both relative and absolute content of lipids were determined using the integrated band area. M.contortum exhibited higher accumulation of lipids than the other two species. The integrated band area of the vibrations from saturated (SFA) and unsaturated lipids (UFA) enabled quantification of fatty acids. The percentage of SFA and UFA was determined using GC, FTIR and Raman spectroscopy. From the spectral data, the order of increasing concentration of SFA among the three microalgal species was M.contortum > Chlamydomonas sp. >Pseudomuriella sp. The spectral results on fatty acids were consistent with the separation of lipids by gas chromatography. The results emphasized the significance of FTIR and Raman spectroscopic methods in monitoring the biomolecular transitions and rapid quantification of lipids, without the need for extraction of lipids.