Chlorella Vulgaris Growth Research Articles

Mixotrophic cultivation of microalgae to enhance the biomass and lipid production with synergistic effect of red light and phytohormone IAA

Microalgal cultivation still presents a big challenge in commercial application due to the small size and low density of microalgae. The effect of phytohormones or light spectra on enhancing microalgal growth has been individually demonstrated at the bench scale. However, the synergistic action of phytohormones and light spectra on algal growth and lipid production remains unclear. In this study, the optimal carbon and nitrogen concentrations, as well as the optimum dosage of the phytohormone indole-3-acetic acid (IAA), for the growth of Chlorella vulgaris were first evaluated under mixotrophic cultivation. A light spectrum experiment was then conducted in an incubator equipped with white and red light. Results show that optimal mixotrophic cultivation conditions were 10 g L−1 glucose, 2250 mg L−1 sodium nitrate and 10 mg L−1 IAA. Under the optimum IAA treatment and irradiation with red light, the highest biomass, lipid content and lipid productivity were 28.34%, 3.53 g L−1 and 140.04 mg L−1 d−1, respectively. As compared to white light, the synergistic action of red light and IAA stimulated biomass production and lipid accumulation by algal cell metabolism and carbon source bioconversion. Furthermore, the post-optimized C. vulgaris had the potential for biodiesel production. These results provide new insights for the highly efficient cultivation of microalgae.

Tubular photobioreactors illuminated with LEDs to boost microalgal biomass production

This work proposes distinct configurations for tubular photobioreactors (PBRs) illuminated with specific and adequate light wavelength provided by LEDs. The PBRs are characterized by an involute/flat reflective surface around/below a cylindrical borosilicate glass tube that is illuminated by a LEDs panel located above. Reflectors can enlarge the absorber tube's illuminated area, enabling a uniform (spatial and temporal) light distribution across the culture vessel. Additionally, high-energy-efficient LEDs can minimize heat generation and energetic-related costs. Coupling these two factors can result in higher light utilization efficiency and photosynthetic activity. Depending on the reflector design, almost all the light arriving at the collector aperture can be collected and available for microalgal cultivation. Chlorella vulgaris (C. vulgaris) growth was evaluated as a function of the reflector geometry (flat (F), simple double parabola (SP) and traditional double parabola (DP)) and material (anodized aluminum with (MS) and without (R85) protective coating and stainless steel (SS)). C. vulgaris growth as a function of time was found to be in good agreement with the actinometric results, where the parabolic reflectors (SP and DP) made of higher specular reflectance materials (R85 and MS) were the most efficient systems. Conversely, energy-based specific growth rates slightly increased as the photon flux decreased, signaling an energetic efficiency loss due to the low transmissibility of microalgal suspensions. Additional tests using two absorber tubes (spaced between 12.5 and 75.0 mm) over the R85-F reflector were also carried out, showing that the distance of 50.0 mm led to the best compromise between the specific growth rates and biomass productivities per square meter of solar collector. Under these conditions, higher efficiency on the photonic energy usage was attained compared to the single-tube test.

Isolation and characterization of α ‐amylase encoding gene in Bacillus amyloliquefaciens PAS

Amylolytic bacteria are a source of amylase, which is an essential enzyme to support microalgae growth in the bioreactor for microalgae culture. In a previous study, the highest bacterial isolate to hydrolyze amylum (namely PAS) was successfully isolated from Ranu Pani, Indonesia, and it was identified as Bacillus amyloliquefaciens. That bacterial isolate (B. amyloliquefaciens PAS) also has been proven to accelerate Chlorella vulgaris growth in the mini bioreactor. This study aims to detect, isolate, and characterize the PAS’s α‐amylase encoding gene. This study was conducted with DNA extraction, amplification of α‐amylase gene with polymerase chain reaction (PCR) method with the specific primers, DNA sequencing, phylogenetic tree construction, and protein modeling. The result showed that α‐amylase was successfully detected in PAS bacterial isolate. The α‐amylase DNA fragment was obtained 1,468 bp and that translated sequence has an identity of about 98.3% compared to the B. amylolyquefaciens α‐amylase 3BH4 in the Protein Data Bank (PDB). The predicted 3D protein model of the PAS’s α‐amylase encoding gene has amino acid variations that predicted affect the protein’s structure in the small region. This research will be useful for further research to produce recombinant α‐amylase.

Analysis of the optimum pH and salinity conditions for the cultivation and biomass production of Chlorella vulgaris from cassava waste

Biofuel serves as an alternative energy to the common fossil fuels currently in use globally and are drawing increasing attention worldwide as substitutes for petroleum-derived transportation fuels to help address challenges associated with petroleum derived fuels. Third generation biofuels, also termed advanced biofuels, are produced from fast growing microalgae and are potential replacements for conventional fuels. The growth and biomass production of these microalgae is dependent on the conditions they are cultivated such as pH and Salinity. Cassava waste mixtures were cultivated on Chlorella vulgaris stock culture at different concentration ratio at ambient temperature, natural light and dark conditions at 670nm absorbance for 14 days. Optimum growth was obtained at 160:40 for cassava peel water to cassava waste water CP:CW. pH variations 6.0, 6.5, 7.0, 7.5, 8.0, 8.5 and 9.0 were checked to determine the optimum pH for the growth and biomass production of Chlorella vulgaris on the optimum cassava waste mixture concentration. It revealed that at pH 6.5, optimal growth and biomass production was achieved, minimal growth was observed at pH 8.0 while minimal biomass was produced at pH 9.0. Salinity variations of 5, 10, 15, 20, 25, 30, 35 and 40 mg/l were used to determine the growth response and biomass production of Chlorella vulgaris. It revealed that salinity variation at 10ppm will be necessary for highest growth on the cassava waste as well as in biomass production. The use of optimal pH and salinity can significantly increase biomass production thus enhancing biofuel production.

C. vulgaris growth batch tests using winery waste digestate as promising raw material for biodiesel and stearin production.

The recovery of high added value compound from waste stream is fundamental to keep biotechnological processes sustainable. In this study, anaerobic digestion of two highly produced organic waste was integrated with microalgae-based processes both to treat liquid digestate and recover high value compounds. Chlorella vulgaris growth was assessed for lipids accumulation and subsequent recovery, using two types of digestate: organic waste and sewage sludge digestate (DIG-OFMSW) and wine lees digestate (DIG-WL). Growth tests were carried out in batch mode and results showed a slightly higher final biomass concentration from DIG-WL (1.36±0.09gl-1) compared to DIG-OFMSW (1.05±0.13gl-1) and a clearly different lipids accumulation yield (28.86±0.05% in DIG-WL compared to 6.1±0.2% of DIG-OFMSW, on total solids). Lipid characterization showed a high oleic acid accumulation (69.52±0.50%w/w in DIG-WL) that positively influence biodiesel properties and a low linolenic acids content (below 0.30%w/w) that comply with European law EN14214 for biodiesel (linolenic acid content lower than 12%w/w). In addition, due to the high concentration of palmitic and stearic acids detected at the end of test, this oil can be used as new substrate to produce stearin, normally produced from palm oil.

Dynamic modelling of microalgae growth under micro-aeration conditions

Microalgae cultivation is a critical prerequisite of biomass and biofuels production, which is conductive to the reduction of fossil energy consumptions, but there are the hydrodynamic challenges. This study proposed a dynamic modelling of microalgae growth using experimental and computational fluid dynamics (CFD) methods. Photosynthesis performances of unicellular microalgae in photobioreactors (PBRs) were investigated. In a regions-dividing airlift PBR-B, flow field and cell-cycle progression of Chlorella vulgaris were studied. It demonstrated adverse effects of the Karman Vortex Street on microalgae exponential growth. High-levels biomass productivity in flow stagnate region emerges. In a PBR-O, cell density and fluorescence intensity of Chlorella vulgaris were elevated by 2.62 % and 46.69 % in the 9th day of cultivation. Therefore, Chlorella vulgaris growth profiles were predicted using this mathematical modelling successfully. It benefits for the retrofits of commercial shear-sensitivity microalgae culture that require aeration in bio-energy industry.

Regulation of carbon source metabolism in mixotrophic microalgae cultivation in response to light intensity variation

Microalgae are one of the promising sources for renewable energy production, and the light intensity variation can affect the biofuel generation and carbon assimilation of mixotrophic microalgae. To reveal the response of carbon assimilation to light intensity, the effect of light intensity on the carbon source metabolism of Chlorella vulgaris under mixotrophic cultivation was investigated in this study. Moreover, the optimal carbon source composition for mixotrophic microalgae cultivation was evaluated using bicarbonate (HCO3−) and carbonate (CO32−) as inorganic carbon sources, and glucose and acetate as organic carbon sources. The optimal light intensity for Chlorella vulgaris growth was at the range of 8000–12000 lux. For the accumulation of biochemical components, low light intensity was beneficial to protein accumulation, and high light intensity was advantageous for carbohydrate and lipid accumulation. With HCO3− and glucose, the maximum lipid content reached 37.0% at a light intensity of 12000 lux. The citrate synthase activity was negatively correlated with light intensity, showing an opposite trend to biomass production. High light intensity had a positive impact on Rubisco expression, which promoted the microalgae growth and carbon fixing. The energy produced by heterotrophic metabolic activities increased at low light intensity, and the enhancement of biomass production with high light intensity was mainly caused by the improved photoreaction efficiency during the mixotrophic cultivation.

Effects of Temperature and Nitrogen Concentration on Growth and Lipid Accumulation of the Green Algae Chlorella vulgaris for Biodiesel

This study investigated the effect of different temperatures and different nitrogen concentrations on the lipid content and biomass of Chlorella microalgae. In this study, algae were cultured in five media with different amounts as 3, 1.5, 0.80, 0.40 g/L, and three temperatures (10, 20, 30 °C). The results of the experiments showed that the optimal temperature and nitrogen concentration for the biomass increase in Chlorella vulgaris are 30°C and 3 g/L, respectively. It was observed that biomass decreased and lipid amount increased due to the decrease in nitrogen concentration. The high lipid amount of 20.80% dry weight (DW) was obtained from the algae produced at 30°C in the free-nitrate medium. The contribution of temperature change to lipid production was not as effective as nitrogen deficiency in the study. According to the fatty acid analysis results made by GC-FID, C. vulgaris seems suitable for biodiesel production because it contains medium-length (C16-C18) fatty acid chains.

Feasibility of the Hybrid Use of Chlorella vulgaris Culture with the Conventional Biological Treatment in Urban Wastewater Treatment Plants

Currently, most wastewater treatment plants do not meet the legal requirements, especially regarding phosphorus and nitrogen contents. In this work, real primary urban wastewater (P-UW) was used as culture medium for the growth of Chlorella vulgaris. Experiments were carried out in batch photobioreactors at laboratory scale. To determine the maximum nutrient removal levels and the optimal pH value for C. vulgaris growth, the following pH values were studied: 5, 6, 7, 8, 9, 10, and 11. Additionally, two control experiments were conducted using UW and tap water at the same conditions but without microalgae inoculation. The operational conditions were agitation rate = 200 rpm, T = 25 °C, aeration rate = 0.5 L/min, and continuous light with illumination intensity = 359 µE m−2 s−1. Significant higher growth was obtained at pH = 7. The direct use of C. vulgaris for P-UW treatment demonstrated high removal percentages of organic (COD and BOD5 removal = 63.4% and 92.3%, respectively) and inorganic compounds (inorganic carbon removal = 99.6%). The final biomass was characterized by an accumulation of high energetic compounds, mainly carbohydrates, which ranged between 63.3% (pH = 5) and 82.8% (pH = 11) and represent a source of biofuels. These new achievements open up the possibility of new horizons in urban wastewater treatment.

Characterization of alginate extracted from Sargassum latifolium and its use in Chlorella vulgaris growth promotion and riboflavin drug delivery

Alginates derived from macroalgae have been widely used in a variety of applications due to their stability, biodegradability and biocompatibility. Alginate was extracted from Egyptian Sargassum latifolium thallus yielding 17.5% w/w. The chemical composition of S. latifolium is rich in total sugars (41.08%) and uronic acids (47.4%); while, proteins, lipids and sulfates contents are 4.61, 1.13 and 0.09%, respectively. NMR, FTIR and TGA analyses were also performed. Crystallinity index (0.334) indicates alginate semicrystalline nature. Sodium alginate hydrolysate was evaluated as Chlorella vulgaris growth promoter. The highest stimulation (0.7 g/L biomass) was achieved by using 0.3 g/L alginate hydrolysate supplementation. The highest total soluble proteins and total carbohydrates were 179.22 mg/g dry wt and 620.33 mg/g dry wt, respectively. The highest total phenolics content (27.697 mg/g dry wt.), guaiacol peroxidase activity (2.899 µmol min−1 g−1) were recorded also to 0.3 g/L alginate hydrolysate supplementation. Riboflavin-entrapped barium alginate-Arabic gum polymeric matrix (beads) was formulated to achieve 89.15% optimum drug entrapment efficiency (EE%). All formulations exhibited prolonged riboflavin release over 120 min in simulated gastric fluid, followed Higuchi model (R2 = 0.962–0.887) and Korsmeyer–Peppas model with Fickian release (n ranges from 0.204 to 0.3885).

Microalgae-based bioremediation of wastewaters - Influencing parameters and mathematical growth modelling

Microalgae have been increasingly recognized as relevant for bioremediation purposes, particularly for wastewater polishing. The implementation of microalgae systems requires efforts on the development of strategies to achieve a cost-effective process. Kinetic models are essential to understand microalgae growth, and for a large-scale implementation and operation under the desired standards. This work aims to assess the influence of wastewater composition, and selected external factors (temperature and photoperiod) on Chlorella vulgaris growth and bioremediation ability. Kinetic models (Monod, Schnute, Logistic, Richards and Gompertz) were used and critically compared to describe the microalga growth under the different operating conditions. The concentration of nitrate was found to be critical for growth under a controlled pH, regardless the presence of micronutrients. A mixotrophic growth, even under low concentrations of glucose, allowed C. vulgaris to be more resilient to variations in temperature and photoperiod, without affecting the bioremediation effectiveness. The microalga shown a low growth ability in acidic wastewaters with ammonium as a nitrogen source. The Monod, Logistic and Gompertz models perfectly fitted the microalga growth. Final results provide a set of conditions and associated kinetic parameters of relevance for C. vulgaris bioremediation as well as highlights the role of the microalga for wastewater polishing.

Interaction Effects of Temperature, Light, Nutrients, and pH on Growth and Competition of Chlorella vulgaris and Anabaena sp. Strain PCC

Interaction effects of temperature, light, nutrients, and pH on growth and competition of Chlorella vulgaris and Anabaena sp. strain PCC were evaluated using an orthogonal design method to elucidate how these environment factors promote the growth of beneficial algae and limit the growth of harmful algae. The optimal conditions for the growth of C. vulgaris in the mono-culture system were as follows: temperature, 35°C; light, 660 lx; N concentration, 0.36 mg L−1; P concentration, 0.1 mg L−1; and pH, 9.0; and those for Anabaena were as follows: temperature, 30°C; light, 6,600 lx; N concentration, 0.18 mg L−1; P concentration, 0.1 mg L−1; and pH, 7.0. The optimal conditions for the growth of C. vulgaris in the co-culture system were as follows: temperature, 25°C; light, 4,400 lx; N concentration, 0.18 mg L−1; P concentration, 0.5 mg L−1; and pH, 6.0; and those for Anabaena were as follows: temperature, 35°C; light, 4,400 lx; N concentration, 0.36 mg L−1; P concentration, 0.5 mg L−1; and pH, 6.0. Both competition-inhibition parameters of Anabaena against C. vulgaris and those of C. vulgaris against Anabaena were the largest under the following conditions: temperature, 30°C; light intensity, 6,600 lx; N concentration, 0.36 mg L−1; P concentration, 0.025 mg L−1; and pH, 8.0. According to the Lotka–Volterra competition model, Anabaena won in the competition in the co-culture system with the following conditions: 1) temperature, 15°C; light, 660 lx; total N (TN), 0.18 mg L−1; total P (TP), 0.025 mg L−1; pH, 6; 2) temperature, 15°C; light, 2,200 lx; TN, 0.36 mg L−1; TP, 0.025 mg L−1; pH, 7; 3) temperature, 15°C; light, 6,600 lx; TN, 3.6 mg L−1; TP, 0.5 mg L−1; pH, 9; 4) temperature, 30°C; light, 4,400 lx; TN, 0.18 mg L−1; TP, 0.05 mg L−1; pH, 9; 5) temperature, 35°C; light, 660 lx; TN, 3.6 mg L−1; TP, 0.05 mg L−1; pH, 8; and 6) temperature, 35°C; light, 2,200 lx; TN, 0.72 mg L−1; TP, 0.025 mg L−1; pH, 9. However, C. vulgaris could not win in the competition in the co-culture system under all conditions tested.

Study of Growth Kinetics of High Lipid Content Algae in Local Environment

In recent years algae has been receiving a lot of interest as an alternate source of biofuel. Fast growth and rich lipid content make algae a great candidate for producing eco-friendly and non-toxic biodiesel. The strain Chlorella vulgaris, has shown great potential as a source of oil. To optimize the mass culture of microalgae Chlorella vulgaris, it is necessary to develop growth kinetic model of Chlorella vulgaris. This work presents a comparative study on growth kinetics of Chlorella vulgaris in batch cultures in four different media, namely- CH, modified CH, Bold’s Basal (BB), and modified Bold’s Basal (BB). Spectroscopic analysis was supported by visual change of color in the algal biomass solution and the microscopic imaging, and was validated with dry cell mass measurement in this study. The data were analyzed to produce growth curves to find exponential phase for each medium. Exponential phases are the best period to harvest the culture. Hence the duration of exponential phase and the final biomass concentration at the end of exponential phase are two important parameters to determine the most suitable medium for mass culture. In this study the overall specific growth, doubling time and biomass productivity of Chlorella vulgaris for CH, modified CH, BB and modified BB media were measured. This study will help to find a suitable media to culture Chlorella vulgaris, a high lipid content algae in the local environment. The information can be used to design a system for mass culture of the strain for biodiesel production.
 Chemical Engineering Research Bulletin 21(2020) 133-138

The Effects of Triclosan on Physiological and Photosynthetic Characteristics of Chlorella vulgaris

Triclosan has been widely used as addition ingredient in personal care and medical antibacterial products, and the increasing amounts of triclosan discharged in aquatic environments pose a potential risk to aquatic ecological systems. In this study, we investigated the effects of exposure to varying triclosan concentrations on the growth, chlorophyll fluorescence and antioxidant enzyme activity of Chlorella vulgaris. The results showed that low-concentration triclosan (<0.75 mg/L) can stimulate the growth of Chlorella vulgaris, whereas 1.05 mg/L triclosan exhibited significant inhibition. Low-concentration triclosan (<0.75 mg/L) could improve the tolerance and utilization ability of Chlorella vulgaris in relation to strong light. We observed a significant increase in the malondialdehyde content of Chlorella vulgaris exposed to 1.05 mg/L triclosan. The intracellular superoxide dismutase and catalase (CAT) activities of Chlorella vulgaris exposed to triclosan were higher than the control groups, and the increase in this activity was positively correlated with the concentration of triclosan. The results also showed that excessive H2O2 may in turn damage the CAT structure and eventually inactivate CAT activity when Chlorella vulgaris is exposed to 1.05 mg/L triclosan. This study provided a theoretical basis which can be used to evaluate the ecological risk of triclosan in the aquatic environment.

Role of ZnO and Fe2O3 nanoparticle on synthetic saline wastewater on growth, nutrient removal and lipid content of Chlorella vulgaris for sustainable production of biofuel

The current investigation highlighted the capability of the Chlorella vulgaris growth in the artificial wastewater with different concentration of NaCl incorporated with difference concentration of nanoparticle ZnO and Fe2O3. Chlorella vulgaris cultured with ZnO and Fe2O3 at the concentration of 5 mg/L, 10 mg/L, 20 mg/L and 50 mg/L. The characterization of the nanoparticles was performed through analytical technique. This study found that, the nutrient removal was effective on ZnO compared to Fe2O3 against total nitrogen and total phosphorous. Further, the NaCl concentration in the wastewater affects the growth of the microalgae and biofuel production. With regard to the biomass concentration, the 20 mg/L ZnO and 50 mg/L Fe2O3 reported highest yield of 2.08 g/L and 2.02 g/L. On the other hand, the maximum lipid accumulation of ZnO and Fe2O3 were 14.25 wt% and 13.8 wt%. Secondly, the procured lipids were processed through transesterification process and characterized by Gas chromatography mass spectrometry (GC–MS). Compelling all the above it is concluded that the Chlorella vulgaris can be the suitable candidate for treatment of wastewater and production of bio-fuel.

Effect of light, CO2 and nitrate concentration on Chlorella vulgaris growth and composition in a flat-plate photobioreactor

The utilization of microalgal biomass for the production of biodiesel and bioethanol is viewed as a promising alternative to increase the offer of both biofuels in the future. In view of this, the autotrophic growth of the green microalga Chlorella vulgaris in a flat-plate photobioreactor was evaluated along with physiological characteristics, such as lipid and carbohydrate composition, and auxiliary parameters of the cultivation using response surface methodology (RSM). Mean biomass productivities of up to 0.262 ± 0.006 g L−1 day−1 were obtained with maximum light intensity and intermediate CO2 concentrations and the microalgal biomass averaged carbohydrate and lipid contents of 8% and 32% respectively. The light flux supplied to the cultivations and the amount of CO2 in the feed gas are variables with significant effect on the mean biomass productivity of the microalgae and help estimate the maximum final biomass concentration possible to be obtained. The behavior of associated parameters, such as increase in medium pH and O2 evolution, was measured and both varied according to different cultivation conditions.

Optimization and qualitative comparison of two vinasse pre-treatments aiming at microalgae cultivation

ABSTRACT The cultivation of microalgae is a possible destination for vinasse, a residue from the sugar and alcohol industry. This use can help reduce the costs of microalgae production and remediate this residue rich in nutrients. However, the physicochemical characteristics of vinasse limit its use for microalgae growth at low concentrations, except when the residue is pretreated. This work aimed at optimizing the vinasse pretreatments of centrifugation and adsorption by smectite clay and activated charcoal on laboratory scale in terms of amounts of materials used and time spent, making them more viable on larger scales. The optimized processes were then compared in productive, economic, and environmental terms. The dilution of treated vinasse with distilled water resulted in similar growth of Chlorella vulgaris to those obtained with the dilution in BG11 medium, indicating that the addition of nutrients in culture media is not necessary. Although microalgae growth occurs in higher concentrations of vinasse treated by adsorption, the results show that centrifugation required less processing time, has cheaper processing costs, and generated much less residue. Centrifugation treatment has greater economic and environmental viabilities and was more sustainable than the adsorption, even though the algae did not grow in the centrifuged residue in concentrations as high as it did after the adsorption treatment. Therefore, this article brings a new view about the economic and environmental aspects on the use of pretreated vinasse for microalgal growth, giving a lucrative destination for a highly polluting waste.

Enhancing microalgae growth and product accumulation with carbon source regulation: New perspective for the coordination between photosynthesis and aerobic respiration

The coordination between photosynthesis and aerobic respiration under mixotrophic cultivation can make a difference to the growth and biochemical composition of microalgae. However, the response of carbon metabolism to carbon source composition under mixotrophic microalgae cultivation has not been well studied. In this study, the synergistic effects of inorganic carbon (IC) and organic carbon (OC) supply on the growth and carbon metabolism of Chlorella vulgaris under mixotrophic cultivation were investigated. The increase of the proportion of HCO3− had a positive effect on the expression of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), which promoted the biomass production and carbon fixing. The activity of citrate synthase was attenuated with the increase of IC/OC ratio, indicating that the energy needed for the biomass production in groups with high IC/OC ratio was contributed by photoreaction. Biochemical analysis showed that CO32− was more efficient than HCO3− for carbohydrate and lipid accumulation of Chlorella vulgaris, and the highest amount of carbohydrate (30.2%) and lipid (35.8%) was recorded with the combined use of CO32− and glucose. The results could provide a new perspective on carbon metabolism and enzyme regulation in mixotrophic microalgae cultivation.

Effects of the antimalarial lumefantrine on Lemna minor, Raphidocelis subcapitata and Chlorella vulgaris

Lumefantrine is used to treat uncomplicated malaria caused by pure or mixed Plasmodium falciparum infections and as a prophylactic against recrudescence following artemether therapy. However, the pharmaceutical is released into the aquatic environment from industrial effluents, hospital discharges, and human excretion. This study assessed the effects of lumefantrine on the growth and physiological responses of the microalgae Chlorella vulgaris and Raphidocelis subcapitata (formerly known as Selenastrum capricornutum and Pseudokirchneriella subcapitata) and the aquatic macrophyte Lemna minor. The microalgae and macrophyte were exposed to 200−10000 μg l−1 and 16−10000 μg l−1 lumefantrine, respectively. Lumefantrine had a variable effect on the growth of the aquatic plants investigated. There was a decline in the growth of R. subcapitata and L. minor post-exposure to the drug. Contrarily, there was stimulation in the growth of Chlorella vulgaris. All experimental plants had a significant increase in lipid peroxidation, which was accompanied by an increase in malondialdehyde content. Peroxidase activity of L. minor increased only at low lumefantrine concentrations, while the opposite occurred at higher levels of the drug. Incubation in lumefantrine contaminated medium significantly up-regulated the activity of R. subcapitata cultures. Glutathione S-transferase of L. minor exposed to lumefantrine treatments had substantially higher activities than the controls. Our findings suggest lumefantrine could have adverse but variable effects on the growth and physiology of the studied aquatic plants.

Municipal Wastewater: A Sustainable Source for the Green Microalgae Chlorella vulgaris Biomass Production

The need to reduce the costs associated with microalgae cultivation encouraged scientific research into coupling this process with wastewater treatment. Thus, the aim of this work was to assess the growth of Chlorella vulgaris (Chlorophyta) in different effluents from a municipal wastewater treatment plant (WWTP), namely secondary effluent (SE) and sludge run-off (SR). Assays were performed, under the same conditions, in triplicate with 4 dilution ratios of the wastewaters (25%, 50%, 75% and 100%) with the standard culture medium bold basal medium double nitrated (BBM2N) as a control. The capability of C. vulgaris for biomass production, chlorophyll synthesis and nutrients removal in the SE and SR was evaluated. The 25% SE and 25% SR showed increased specific growth rates (0.47 and 0.55 day−1, respectively) and higher biomass yields (8.64 × 107 and 1.95 × 107 cells/mL, respectively). Regarding the chlorophyll content, the 100% SR promoted the highest concentration of this pigment (2378 µg/L). This green microalga was also able to remove 94.8% of total phosphorus of SE, while in 50% SR, 31.2% was removed. Removal of 73.9% and 65.9% of total nitrogen in 50% and 100% SR, respectively, was also observed. C. vulgaris growth can, therefore, be maximized with the addition of municipal effluents, to optimize biomass production, while cleansing the effluents.