The Biosorption Capacity of the Marine Microalga Phaeodactylum tricornutum for the Removal of Toluidine Blue from Seawater.

A wide variety of dyes, such as toluidine blue (TB), are used daily for a multitude of purposes. After use, many of these compounds end up in aqueous effluents, reaching natural environments, including marine environments. The removal of these pollutants from marine environments must be considered a priority problem. The search for natural techniques, such as biosorption, is a preferred option to eliminate pollution from natural environments. However, biosorption studies in seawater are scarce. For this reason, the living biomass of the marine microalga Phaeodactylum tricornutum was studied to determine its ability to remove TB from seawater. The kinetics of the biosorption process, the isotherms, and the effect of light and pH were determined. This biomass showed a maximum TB removal capacity of 45 ± 2 mg g-1 in the presence of light. Light had a positive effect on the TB removal capacity of this living biomass. The best fitting kinetics was the pseudo-second order kinetics. The efficiency of the removal process increased with increasing pH. This removal was more effective at alkaline pH values. The results demonstrated the efficacy of P. tricornutum living biomass for the efficient removal of toluidine blue dye from seawater both in the presence and absence of light.

Efficient Removal of Methylene Blue Using Living Biomass of the Microalga Chlamydomonas moewusii: Kinetics and Equilibrium Studies.

The efficiency of the living biomass of the microalga Chlamydomonas moewusii in removing methylene blue dye is determined. The kinetics, equilibrium isotherms, and the effects on this process of the pH, contact time, and initial concentration of the dye are studied. Fourier transform infrared spectrometry and point of zero charge are used to characterize the biomass and explore the process. The maximum removal capacity derived from the Langmuir isotherm is 212.41 ± 4.55 mg/g after 7 h of contact time at pH 7. The removal process is rapid because kinetic studies revealed that the best fit of the data is with pseudo-third-order kinetics. The removal efficiency is dependent on the pH; as the pH increased, the efficiency is higher. These results show that the living biomass of this microalga is a very efficient biosorbent and therefore very suitable for the removal of methylene blue from aqueous solutions.

Eco-friendly rapid removal of triclosan from seawater using biomass of a microalgal species: Kinetic and equilibrium studies.

Triclosan is an important emerging pollutant. It has become ubiquitous due to its incomplete elimination in municipal wastewater treatment plants causing serious environmental problems. Biomass from microorganisms as sorbent of pollutants can be an eco-friendly alternative for triclosan removal. In this work, the elimination of triclosan using biomass (dead and living) of the marine microalga Phaeodactylum tricornutum was characterized in cultures exposed to light and in a complex solution (seawater). Maximum removal capacity, isotherms, kinetics, FTIR characterization, pH effect and reuse were evaluated and discussed. Photodegradation of triclosan was also evaluated. Both biomasses showed similar effectiveness; around 100% of pollutant was eliminated when its concentration was 1 mg L-1 in only 3 h using a biomass concentration of 0.4 g L-1. A pseudo-second order model guided the biosorption process. Considering the photodegradation as a first-order process, the whole process (photodegradation + biosorption) was suitably modelled with pseudo-third order and Elovich kinetics. Biosorption increased with the decrease in pH. Temkin isotherm showed the best fit for the experimental data. Both biomasses showed good reuse after five cycles, losing only 7% in efficiency. P. tricornutum biomass is an attractive eco-material for triclosan elimination with low-cost and easy handling than other sorbents.

Bioremediation of oxytetracycline in seawater by living and dead biomass of the microalga Phaeodactylum tricornutum.

Due to its use, a large amount of Oxytetracycline (OTC) is released into water, which has a detrimental impact on aquatic ecosystems and human health. Although there are different physicochemical methods (mainly photodegradation) to remove OTC, there is increasing interest in the use of bioremediation. The sorption characteristics of OTC using living and dead biomass of the microalga Phaeodactylum tricornutum have been investigated in this study. Kinetics, isotherms and maximum elimination capacity were tested and discussed. Kinetic studies showed that the OTC removal by living biomass followed a sigmoidal model. However, the dead biomass followed a pseudo-first order model. The living biomass showed higher efficiency than the dead biomass with maximum sorption capacities of 29.18mgg-1 and 4.54mgg-1, respectively. Combination of living biomass and photodegradation under the culture conditions eliminated 13.2mgL-1 of OTC during 11h of culture and with an initial OTC concentration of 15mgL-1. With an initial OTC concentration of 2.5mgL-1, 97% of OTC was removed. This removal was mainly caused by bioremediation than by photodegradation. The results proved the potential practical application of the living P. tricornutum biomass for a low-cost and efficient removal of OTC from seawater.

Influence of sulphate on the reduction of cadmium toxicity in the microalga Chlamydomonas moewusii.

Cadmium is considered as one of the most hazardous metals for living organism and ecosystems. Environmental factors play an important role since they alter the toxicity of metals by varying the bioavailability of these elements for the organisms. The aim of the present study was to investigate, using the freshwater microalga Chlamydomonas moewusii, the existence of an interaction between cadmium and sulphate as a factor that varied the toxicity of this metal. Different cell parameters such as cell growth, content of chlorophylls and biosynthesis of phytochelatins (PCs) were determined. A two-way ANOVA showed that the interaction had a significant effect size of 21% (p<0.001) for the growth of this microalga and around of a 6% on the content of chlorophylls/cell. The effect of this inhibition was that when the concentration of sulphate increased, a lower toxic effect of cadmium on the growth and on the content of chlorophylls was observed. In addition, the increase of sulphate concentration allowed the biosynthesis of a higher amount of PCs and/or PCs with higher chain length. This higher biosynthesis was responsible for the reduction of the toxic effect of cadmium and explained the interaction.

Effects of sodium sulfate on the freshwater microalga Chlamydomonas moewusii: implications for the optimization of algal culture media.

The study of the microalgal growth kinetics is an indispensable tool in all fields of phycology. Knowing the optimal nutrient concentration is an important issue that will help to develop efficient growth systems for these microorganisms. Although nitrogen and phosphorus are well studied for this purpose, sulfur seems to be less investigated. Sulfate is a primary sulfur source used by microalgae; moreover, the concentration of this compound is increasing in freshwater systems due to pollution. The aim of this study was to investigate the effects of different sodium sulfate concentrations in the culture medium on growth and growth kinetics of the freshwater microalga Chlamydomonas moewusii. Production of biomass, chl content, kinetic equations, and a mathematical model that describe the microalgal growth in relation with the concentration of sodium sulfate were obtained. The lowest concentration of sodium sulfate allowing optimal growth was 0.1 mM. Concentrations higher than 3 mM generated a toxic effect. This work demonstrates that this toxic effect was not directly due to the excess of sulfate ion but by the elevation of the ionic strength. An inhibition model was successfully used to simulate the relationship between specific growth rate and sodium sulfate in this microalga.

Isobolographic analysis of the interaction between cadmium (II) and sodium sulphate: toxicological consequences.

Sulphate is an essential nutrient for autotrophic organisms and has been shown to have important implications in certain processes of tolerance to cadmium toxicity. Sodium sulphate is the main salt of sulphate in the natural environments. The concentration of this salt is increasing in the aquatic environments due to environmental pollution. The aim of this study was to investigate, using an analysis of isobolograms, the type and the degree of the interaction between Cd(II) and sodium sulphate in the freshwater microalga Chlamydomonas moewusii. Two blocks of experiments were performed, one at sub-optimal sodium sulphate concentrations (<14.2 mg/L) and the other at supra-optimal concentrations (>14.2 mg/L). Three fixed ratios (2:1, 1:1, and 1:2) of the individual EC50 for cadmium and sodium sulphate were used within each block. The isobolographic analysis of interaction at sub-optimal concentrations showed a stronger antagonistic effect with values of interaction index (γ) between 1.46 and 3.4. However, the isobologram with sodium sulphate at supra-optimal concentrations revealed a slight but significant synergistic effect between both chemicals with an interaction index between 0.54 and 0.64. This synergic effect resulted in the potentiation of the toxic effects of cadmium, synergy that was related to the increase of the ionic strength and of two species of cadmium, CdSO4 (aq), and Cd(SO4)2(2-) , in the medium. Results of the current study suggest that sodium sulphate is able to perform a dual antagonist/synergist effect on cadmium toxicity. This role was concentration dependent.

Isotherm studies for the determination of Cd (II) ions removal capacity in living biomass of a microalga with high tolerance to cadmium toxicity.

The biosorption characteristics of Cd (II) ions using the living biomass of the marine diatom Phaeodactylum tricornutum were investigated. This microalga is a highly tolerant species to cadmium toxicity; for this reason, it is interesting to know its potential for use in the removal of this metal. The use of living biomass offers better possibilities than that of dead biomass since cadmium can also be bioaccumulated inside the cells. For this purpose, tolerant species are necessary. P. tricornutum is within this category with an EC50,96h of 19.1 ± 3.5 mg Cd (II)/L, and in the present manuscript, it is demonstrated that this microalga has a very good potential for bioremediation of Cd (II) ions in saline habitats. Cadmium removed by the cells was divided into three fractions: total, intracellular and bioadsorbed. The experiments were conducted for 96 h in natural seawater with a concentration range of 1-100 mg Cd (II)/L. Each fraction was characterized every 24 h by sorption isotherms. The experimental isotherm data were analyzed using the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin equations. The biosorption was well described by Langmuir isotherm followed by Freundlich. The worst model was Temkin. The biosorption capacity of this microalga for Cd (II) ions was found to be 67.1 ± 3.2 mg/g after 96 h with approximately 40 % of this capacity in the intracellular fraction. The bioconcentration factor determined was 2,204.7 after 96 h and with an initial Cd (II) concentration of 1 mg/L.

Sulphate, more than a nutrient, protects the microalga Chlamydomonas moewusii from cadmium toxicity.

Sulphur is an essential macroelement that plays important roles in living organisms. The thiol rich sulphur compounds, such as cysteine, γ-Glu-Cys, glutathione and phytochelatins participate in the tolerance mechanisms against cadmium toxicity. Plants, algae, yeasts and most prokaryotes cover their demand for reduced sulphur by reduction of inorganic sulphate. The aim of this study was to investigate, using a bifactorial experimental design, the effect of different sulphate concentrations in the nutrient solution on cadmium toxicity in the freshwater microalga Chlamydomonas moewusii. Cell growth, kinetic parameters of sulphate utilization and intracellular concentrations of low-molecular mass thiol compounds were determined. A mathematical model to describe the growth of this microalga based on the effects of sulphate and cadmium was obtained. An ANOVA revealed an interaction between them, 16% of the effect sizes was explained by this interaction. A higher amount of sulphate in the culture medium allowed a higher cadmium tolerance due to an increase in the thiol compound biosynthesis. The amount of low-molecular mass thiol compounds, mainly phytochelatins, synthesized by this microalga was significantly dependent on the sulphate and cadmium concentrations; the higher phytochelatin content was obtained in cultures with 4 mg Cd/L and 1mM sulphate. The maximum EC50 value (based on nominal cadmium concentration) reached for this microalga was 4.46 ± 0.42 mg Cd/L when the sulphate concentration added to the culture medium was also 1mM. An increase in the sulphate concentration, in deficient environments, could alleviate the toxic effect of this metal; however, a relative excess is also negative. The results obtained showed a substrate inhibition for this nutrient. An uncompetitive model for sulphate was chosen to establish the mathematical model that links both factors.

Cadmium toxicity on the freshwater microalga Chlamydomonas moewusii Gerloff: Biosynthesis of thiol compounds.

Cadmium (Cd) toxicity and production of different thiols (phytochelatins, glutathione, gamma-Glu-Cys and cysteine) were studied in the microalga Chlamydomonas moewusii exposed to different concentrations of this metal (1, 2, 4, 6, 8, and 10 mg/L) for 96 h. The inhibitory effect of Cd on growth was demonstrated. The value of EC50 (metal concentration which reduces the population growth to 50% of the control) obtained for this microalga was estimated at 4.1 +/- 0.8 mg/L of Cd after 96 h of exposure. The amount of thiol compounds synthesized by C. moewusii changed with Cd concentration. Cysteine concentrations were significantly higher compared to those of gamma-Glu-Cys and glutathione in all the Cd concentrations assayed. The amino acid cysteine reached its higher levels in those cultures in which a decrease in the concentration of phytochelatins (PCs) was observed. Both cysteine and glutathione concentrations showed significant differences along the Cd concentrations assayed, while the amount of gamma-Glu-Cys detected remained stable. The PCs detected were of two, three, and four subunits. The level of PC(2) was higher than that of PC(3) and PC(4). PC(4) was detected only in the cultures exposed to the Cd concentrations of 1 and 2 mg/L, in which the synthesis of phytochelatins was higher. A rapid increase in the production of PC(2) and PC(3) was observed up to a Cd concentration of 2 mg/L, after which their levels began to decrease. Phytochelatins were not detected in cultures without Cd (controls) and in those exposed to the maximum Cd concentration (10 mg/L), in which cell growth was completely inhibited.

A capillary zone electrophoresis for determination of thiolic peptides in biological samples.

A new method to improve the analyses of thiolic peptides (cysteine, gammaGlu-Cys, glutathione, phytochelatins and desglycyl-phytochelatins) derivatized with monobromobimane (mBrB) in complex biological samples by CZE is described. The method involves a SPE using Sep-Pak Light C18 Cartridges after derivatization and a later CZE analysis. Elution of mBrB-thiols was achieved with 10 mM HCl + 70% methanol v/v in deionised water. Electrophoretic parameters, such as BGE pH and concentration, different organic additives (methanol and trifluoroethanol), applied voltage and capillary length were studied in order to establish suitable analytical conditions. Optimum separation of the mBrB-thiolic peptides was obtained with 100 mM sodium borate buffer at pH 7.60. The electrophoretic conditions were +15 kV, capillary length of 90 cm from inlet to detector (98 cm total length, 50 microm ID), samples were loaded into the capillary by hydrodynamic injection (50 mbar, 20 s) and detection was performed at 390 nm. The improved method showed good reproducibility, linearity and sensitivity. The LODs and LOQs estimated using a standard of GSH were 1.41 and 4.69 microM respectively.