Freshwater Microalga Scenedesmus Sp Research Articles

Efficient removal of thiamethoxam by freshwater microalgae Scenedesmus sp. TXH: Removal mechanism, metabolic degradation and application

Neonicotinoids, as the most widely used pesticides in the world, help improve the production of crops. Meanwhile, it also brings potential threats to surrounding environments and other organisms because of its wide use and even abuse. In this study, Scenedesmus sp. TXH isolated from a wastewater treatment plant was used to remove the neonicotinoid pesticide thiamethoxam (THIA). The removal efficiency, degradation pathway, metabolite fate of THIA and physicochemical effects on microalgae cells were studied. Meanwhile, the feasibility of using microalgal technology to remove THIA from municipal wastewater was also explored. The results showed that 5–40 mg/L of THIA slightly promoted the growth of microalgae, while 60 mg/L THIA severely inhibited microalgal growth. It was observed that malondialdehyde content and superoxide dismutase activity in 60 mg/L THIA group increased significantly (p < 0.05) in the early stage of the experiment, indicating that THIA caused oxidative damage to microalgae. Scenedesmus sp. TXH showed high-efficient degradation ability and high resistance to THIA, with 100% removal of THIA at 5, 20 and 40 mg/L groups and 97.5% removal of THIA at 60 mg/L group on day 12. THIA was mainly removed by biodegradation, accounting for 78.18%, 93.50%, 96.81% and 91.35% under 5, 20, 40 and 60 mg/L on day 12, respectively. Six degradation products were identified, and four potential degradation pathways were proposed. In practical wastewater, the removal efficiency of total dissolved nitrogen, total dissolved phosphorus, ammonia nitrogen and THIA reached 85.68%, 90.00%, 98.43% and 100%, respectively, indicating that Scenedesmus sp. TXH was well adapted to the wastewater and effectively removed THIA and conventional pollutants.

Efficient Removal of Imidacloprid by Freshwater Microalgae Scenedesmus Sp. Txh: Effects and the Biodegradation Pathway

Efficient Removal of Imidacloprid by Freshwater Microalgae Scenedesmus Sp. Txh: Effects and the Biodegradation Pathway

Effect of Mild Salinity Stress on the Growth, Fatty Acid and Carotenoid Compositions, and Biological Activities of the Thermal Freshwater Microalgae Scenedesmus sp.

Carotenoids have strong antioxidant activity as well as therapeutic value. Their production has been induced in algae under stressful culture conditions. However, the extreme culture conditions lead to the Programmed Cell Death (PCD) of algae, which affects their growth and productivity. This study was performed to evaluate the effect of salinity on the physiological and biochemical traits of Scenedesmus sp., thermal freshwater microalgae from Northern Tunisia. It was cultured under different NaCl concentrations ranging from 0 to 60 g/L. Results showed a good growth and high contents of total chlorophyll and carotenoids in Scenedesmus sp. cultured at 10 g/L of NaCl (salt-stressed 10 (Ss10)). The pigment composition of the Ss10 extract was acquired using HPLC–MS, and showed that the carotenoid fraction is particularly rich in xanthophylls. Moreover, the antioxidant (DPPH and FRAP) and enzymatic inhibition (tyrosinase and elastase) activities of the Ss10 extract were higher compared to those of the control culture. In addition, the cytotoxicity test on B16 cells showed that the Ss10 extract was non-toxic for all tested concentrations below 100 µg/mL. It also showed a rich unsaturated fatty acid (FA) composition. Therefore, these findings suggest that Scenedesmus sp. strain cultivated under mild stress salinity could be a source of biomolecules that have potential applications in the nutraceutical and cosmeceutical industries.

Media optimization for cultivation freshwater microalga Scenedesmussp. under controlled conditions.

Media optimization for cultivation freshwater microalga Scenedesmussp. under controlled conditions.

The “Fingerprint” of a freshwater microalga Scenedesmus sp. LX1: Visualizing the composition of its soluble algal products

In this study, a fingerprint analysis method along with the EEM fluorescence spectra was used to characterize the SAPs released by Scenedesmus sp. LX1 during the growth process. Resin fractionation was used firstly to divide the SAPs into six resin fractions, and then size exclusion chromatography (SEC) was performed to separate each resin fraction into several subfractions with different molecular weights (MW). The fingerprint graph integrated the information revealed by resin fractionation as well as that by SEC, showing that main components of SAPs changed from the hydrophilic subfractions with MW of 102-103 Da to the hydrophobic subfractions with MW of 103-104 Da. Comparing these results with the EEM fluorescence spectra of different resin fractions, the change of the main matters within SAPs could be inferred.

NMR-Based Metabolomic Approach To Elucidate the Differential Cellular Responses during Mitigation of Arsenic(III, V) in a Green Microalga.

Nuclear magnetic resonance (NMR)-based metabolomic approach is a high-throughput fingerprinting technique that allows a rapid snapshot of metabolites without any prior knowledge of the organism. To demonstrate the applicability of NMR-based metabolomics in the field of microalgal-based bioremediation, novel freshwater microalga Scenedesmus sp. IITRIND2 that showed hypertolerance to As(III, V) was chosen for evaluating the metabolic perturbations during arsenic stress in both its oxidation states As(III) and As(V). Using NMR spectroscopy, we were able to identify and quantify an array of ∼45 metabolites, including amino acids, sugars, organic acids, phosphagens, osmolytes, nucleotides, etc. The NMR metabolomic experiments were complemented with various biophysical techniques to establish that the microalga tolerated the arsenic stress using a complex interplay of metabolites. The two different arsenic states distinctly influenced the microalgal cellular mechanisms due to their altered physicochemical properties. Eighteen differentially identified metabolites related to bioremediation of arsenic were then correlated to the major metabolic pathways to delineate the variable stress responses of microalga in the presence of As(III, V).

Surface-Active Ionic Liquid Cholinium Dodecylbenzenesulfonate: Self-Assembling Behavior and Interaction with Cellulase.

The conventional sodium dodecylbenzenesulfonate (NaDBS) has been converted into an efficient and nontoxic anionic surface-active ionic liquid, cholinium dodecylbenzenesulfonate (Cho[DBS]). We have investigated its self-assembling behavior, interaction with the enzyme cellulase, and ecotoxicity. The surface-active properties at the air–liquid interface and the aggregation behavior of Cho[DBS] in water have been determined using tensiometry, isothermal titration calorimetry (ITC), conductometry, and dynamic light scattering (DLS). The enzyme activity was observed using dinitro salicylic acid analysis. The enhanced enzyme activity was explained through active-site exfoliation and structural constancy of cellulase in the micellar medium using the results from fluorescence, circular dichroism, DLS, and ITC. The nontoxic nature was confirmed by toxicity analysis on the freshwater microalgae Scenedesmus sp.

Enhanced growth and fatty acid accumulation of microalgae Scenedesmus sp. LX1 by two types of auxin

Microalgae are potential candidates for the production of valuable products, such as renewable biodiesel, health products and pigments. However, low biomass productivity has restricted their large-scale applications. In this study, the effects of two auxins (one natural type of indole-3-acetic acid (IAA) and the other synthetic type of 2,4-dichlorophenoxyacetic acid (2,4-D)) on the growth and fatty acid methyl esters (FAMEs) production of a freshwater microalgae Scenedesmus sp. LX1 were investigated. Both auxins showed a “low dosage-promotion and high dosage-inhibition” effect on the growth and FAMEs accumulation. The optimum dosage of IAA and 2,4-D were 1mgL−1 and 0.1mgL−1, respectively. Moreover, the IAA could increase the monounsaturated fatty acid content. The auxins may promote the growth by enhancing the photosynthetic activity through increasing chlorophyll contents. Therefore, auxin significantly enhanced microalgal growth and FAMEs accumulation, and has a potential for application in developing efficient microalgal cultivation.

Effects of fish silage on growth and biochemical characteristics of fresh water microalga Scenedesmus sp. MB 23

Scenedesmus sp. MB 23 was cultivated in fish silage to study the effects of different concentrations on the growth and biochemical characteristics, particularly the protein, carbohydrate and lipid properties. Fish silage with 12% concentration was most effective for the growth and biomass production of Scenedesmus sp. The microalga reached maximum cell density (2433.89 × 104 cells/mL), chlorophyll-a concentration (2.766 μg/mL), specific growth rate (0.48/d) and biomass (2.73 g/L) on this medium. In mass culture, enhanced production of protein (123.87 mg/g dry weight of alga), carbohydrate (44.904 mg/g dry weight of alga) and lipid (84.21 mg/g dry weight of alga) was found using 9% fish silage. The effective reduction (up to 90%) in the concentrations of nitrate, phosphorus and ammonia in the final fish silage medium proved the removal efficiency of Scenedesmus sp. The enhanced production of Scenedesmus sp. MB 23 indicated that effective bioremediation of fish waste can be conducted using algal mass production in fish silage. The study also proved that microalgae grown in fish silage have great industrial potential and can be used as a source of feed and biofuel.

Accumulation characteristics of soluble algal products (SAP) by a freshwater microalga Scenedesmus sp. LX1 during batch cultivation for biofuel production

Algae cultivation is the essential basis for microalgal biofuel production. Soluble algal products (SAP) are significant obstacle to large-scale, high-cell-density cultivation processes. SAP accumulation during batch cultivation of Scenedesmus sp. LX1 (a unique strain accumulating lipid substantially while growing fast under low-nutrient conditions) with different initial nitrogen concentrations (7.4–34.0mgNL−1) was investigated. The SAP content varied in the range of 3.4–17.4mgDOCL−1 at stationary phase, with average yield per cell of 0.5–2.5pgDOCcell−1. High SAP accumulation up to 15.2–17.4mgDOCL−1 were observed with initial nitrogen above 20.2mgNL−1. The maximum SAP production rate per unit culture volume (rSAP) was 2.6mgDOC(Ld)−1 and that per cell (νSAP) was 1.5pgDOC(celld)−1. The rSAP increased with cell growth rate and decreased with cell density linearly. The SAP accumulation was majorly due to the release of growth-associated products.

Growth and lipid accumulation properties of a freshwater microalga Scenedesmus sp. under different cultivation temperature

Microalgal lipid is a promising feedstock for biodiesel production. Effect of cultivation temperature on the growth and lipid accumulation properties of a freshwater microalga Scenedesmus sp. LX1 was studied. Scenedesmus sp. LX1 could grow in a wide range of temperature (10∼30°C), and the growth activation energy was 49.3 kJ·mol(-1). The optimal temperature to produce microalgal biomass and lipid was 20°C, and after 15 days of batch cultivation the productivities of 313.3 g biomass·(g P)(-1), 112 g lipid (g P)(-1) and 14.7 g TAGs·(g P)(-1) were obtained. The content of polyunsaturated fatty acids decreased with the increase of cultivation temperature. The reactive oxygen species (ROS) levels at 10°C and 20°C were higher than that under higher temperature. For the first time the cultivation temperature, ROS level, specific growth rate and lipid content per microalgal biomass were correlated together.

Effects of different nitrogen and phosphorus concentrations on the growth, nutrient uptake, and lipid accumulation of a freshwater microalga Scenedesmus sp.

Microalgae have high potential to remove inorganic nutrients from wastewater and to produce biodiesel. Effects of nitrogen and phosphorus concentrations on growth, nutrient uptake, and lipid accumulation of a freshwater microalga Scenedesmus sp. LX1 were studied. Scenedesmus sp. LX1’s growth was in accordance with the Monod model. The following Monod parameters were obtained: the N- and P-saturated maximum growth rate was 2.21 × 10 6 cells mL −1 d −1, and the half-saturation constants of N and P uptake were 12.1 mg L −1 and 0.27 mg L −1, respectively. In the nitrogen/phosphorus ratio of 5:1–12:1, 83–99% nitrogen and 99% phosphorus could be removed. In conditions of nitrogen (2.5 mg L −1) or phosphorus (0.1 mg L −1) limitation, Scenedesmus sp. LX1 could accumulate lipids to as high as 30% and 53%, respectively, of its algal biomass. The lipid productivity/unit volume of culture, however, was not enhanced. Further research should be made on how to enhance both lipid content and lipid productivity.

Growth and nutrient removal properties of a freshwater microalga Scenedesmus sp. LX1 under different kinds of nitrogen sources

Microalgae have received much attention for the inorganic nutrient removal in tertiary treatment of domestic wastewater. Effect of different kinds of nitrogen sources on the growth and nitrogen/phosphorus removal properties of a newly isolated freshwater microalga, Scenedesmus sp. LX1, from a low-nutrient environment condition was studied and reported in this paper. The order of specific growth rate of the microalga with different nitrogen sources was NH 4-N > urea-N > NO 3-N. With nitrate or urea as nitrogen source, the microalga could grow well and remove both nitrogen and phosphorus efficiently (90% nitrogen and nearly 100% phosphorus were removed). However, with ammonium as the nitrogen source, the maximum algal density was relatively low, and the nitrogen and phosphorus removal efficiencies were as low as 31.1% and 76.4%, respectively. This was caused by the inhibitory effect of algal culture's acid pH due to H + releasing from NH 4 + during algal cultivation process.