Scenedesmus Quadricauda Research Articles

Evaluation of an electro-flotation-oxidation process for harvesting bio-flocculated algal biomass and simultaneous treatment of residual pollutants in coke wastewater following an algal-bacterial process

This study investigated the feasibility of employing an electro-flotation-oxidation process that employs a pair of boron-doped diamond (BDD) and aluminum (Al) electrodes for electrochemical harvesting of green microalgae (Scenedesmus quadricauda) and treatment of residual pollutants in coke effluent, following an algal-bacterial process. Electro-coagulation-flotation with polarity exchange and with direct electro-flotation at 15mAcm−2 or more for 40min allowed almost complete harvesting of microalgae. Similar harvesting efficiencies were achieved using direct electro-flotation, without electro-coagulation, under different electrical densities because algal biomass formed flocs with the other microorganisms in the activated sludge (AS). These results also indicate that the proposed approach of inducing bioaggregation via floc-forming microorganisms with microalgae is an efficient alternative to chemical flocculation, because it can minimize the release of toxic metal coagulants during electrochemical harvesting. During sequential electro-oxidation, anodic oxidation using the BDD electrode simultaneously mineralized residual soluble chemical oxygen demand (SCOD) and thiocyanate (SCN−), which are not degraded by algal-bacterial mixed cultures. Although the degradation rate of SCN− was much higher than that of SCOD under certain current densities, further investigation is needed to clarify the mechanism of SCN− mineralization during BDD-anodic oxidation. To satisfy the standard level of electrical power consumption for wastewater treatment, an electric current density below 15mAcm−2 must be supplied. The proposed electrochemical approach involving bioflocculation could be used as an efficient post treatment of microalgae-mediated process for treating coke wastewater.

Ionic liquids toxicity on fresh water microalgae, Scenedesmus quadricauda, Chlorella vulgaris &Botryococcus braunii; selection criterion for use in a two-phase partitioning bioreactor (TPPBR)

A promising method of Carbon dioxide (CO2) valorization is to use green microalgae photosynthesis to process biofuel. Two Phase Partitioning Bioreactors (TPPBR) offer the possibility to use non-aqueous phase liquids (NAPL) to enhance CO2 solubility; thus making CO2 available to maximize algae growth. This requires relatively less toxic hydrophobic Ionic Liquids (ILs) that comprise a new class of ionic compounds with remarkable physicochemical properties and thus qualifies them as NAPL candidates. This paper concerns the synthesis of ILs with octyl and butyl chains as well as different cations containing aromatic (imidazolium, pyridinium) and non-aromatic (piperidinum, pyrrolidinium) rings for CO2 absorption studies. The authors measured their respective toxicity levels on microalgae species, specifically, Scenedesmus quadricauda, Chlorella vulgaris and Botryococcus braunii.Results revealed that octyl-based ILs were more toxic than butyl-based analogues. Such was the case for bmim-PF6 at double saturation with an absorbance of 0.11, compared to Omim-PF6 at 0.17, bmim-NTf2 at 0.02, and Omim-NTf2 at 0.14, respectively. CO2 uptake results for ILs bearing octyl-based chains compared to the butyl analog were 54% (nCO2/nIL) (i.e., moles of CO2 moles of IL) and 38% (nCO2/nIL), respectively.Conclusively, 1-butyl-1-methylpiperidinium absorbed 13% (nCO2/nIL) and appeared the least toxic, having an absorbance of 0.25 at 688 nm (double saturation at 7 d) compared to 1-butyl-3-methylimidazolium, which showed the highest toxicity with zero absorbance. Accordingly, these findings suggest that 1-butyl-1-methylpiperidinium is capable of transporting CO2 to a system containing green microalgae without causing significant harm; thus allowing its use in TPPBR technology.

Single cell lipid profiling of Scenedesmus quadricauda CASA-CC202 under nitrogen starved condition by surface enhanced Raman scattering (SERS) fingerprinting

Oleaginous microalgae tend to accumulate neutral lipids as their energy reserve mainly in the form of triacylglycerol (TAG) which can be utilized as the precursor molecule for biodiesel and other nutraceutical application. The TAG level and the fatty acid composition of microalgae modulated by exposing the algal strains to different physicochemical, nutritional and environmental factors. Nitrogen starvation is considered as an important and practically feasible way by which the lipid content can be enriched in large scale production. In the present investigation, Scenedesmus quadricauda CASA-CC202, oleaginous microalgae with high biomass productivity has been subjected to nitrogen starvation and the stress mediated lipids were analyzed on a single cell basis. As a new insight, we have successfully identified the unsaturated and saturated functionalities of fatty acids by surface enhanced Raman scattering (SERS) spectral footprint under nitrogen starved condition in acidic and, neutral pH. In addition, other macromolecules like chlorophyll, carotenoids, proteins and carbohydrates were also selectively mapped. Most promising SERS mapping pattern of single algal cells depicts high lipid rich component under nitrogen starved condition and degree of unsaturation vs. saturation has been validated through SERS spectral analysis by comparing with the Raman spectra of standard fatty acids. Moreover, the present investigation, clearly distinguish the lipids from other macromolecules like protein, carbohydrate and photosynthetic pigments in whole cell. Finally, SERS based analysis dually by spectral and mapping techniques of lipid enriched S. quadricauda CASA-CC202 has been superimposed with Nile red staining of the same algal cells which unambiguously identify the neutral lipid components under the starved condition.

Ascorbic acid affects short-term response of Scenedesmus quadricauda to cadmium excess

Impact of ascorbate biosynthetic inhibitor (lycorine, LYC) on short-term cadmium (Cd) action (1h, 100μM) was studied in the green alga Scenedesmus quadricauda with 1h or 24h of LYC co-application. LYC suppressed Cd-induced increase in ascorbic acid and enhanced oxidative symptoms (ROS fluorescence) by modulating activities of antioxidative enzymes after 24h of addition (decrease in superoxide dismutase, catalase and ascorbate peroxidase activities). Prolonged (24h) exposure to LYC also affected content of Cd and quantitative changes of thiols (glutathione and phytochelatin 2) while Cd itself revealed interesting responses in algae maintained in the buffer for various time: these data indicate that in the studies involving axenic algal cultures, transfer of cells from sterile to non-sterile conditions modulates metal uptake. Among aliphatic organic acids, α-ketoglutaric, lactic and malic acids were variously influenced by Cd or lycorine, suggesting shift in the respiration and fermentation. It is concluded that ascorbic acid is involved in the protection of cells against Cd-induced ROS over-accumulation and metabolic changes were more expressive in the samples with 24h co-application of LYC though side impacts of LYC cannot be excluded. DESI-Orbitrap MS for the identification and visualization of lycorine was also successfully tested here for the first time.

Biodegradation of naproxen by freshwater algae Cymbella sp. and Scenedesmus quadricauda and the comparative toxicity

Naproxen is one of the most prevalent pharmaceuticals and of great environment concern. Information about bioremediation of naproxen by algae remains limited and no study has been reported on the degradation mechanism and the toxicity of NPX on algae. In this study, both Cymbella sp. and Scenedesmus quadricauda showed complete growth inhibition (100%) at 100mgL−1 within 24h. Biochemical characteristics including chlorophyll a, carotenoid contents and enzyme activities for these two microalgae were affected by NPX at relatively high concentrations after 4d of exposure. Degradation of naproxen was accelerated by both algae species. Cymbella sp. showed a more satisfactive effect in the bioremediation of NPX with higher removal efficiency. A total of 12 metabolites were identified by LC-MS/MS and the degradation pathways of naproxen in two algae were proposed. Hydroxylation, decarboxylation, demethylation, tyrosine conjunction and glucuronidation contributed to naproxen transformation in algal cells.

Effects of biocide treatments on durability of wood and bamboo/high density polyethylene composites against algal and fungal decay

ABSTRACTThe main objective of this study was to investigate the algal and fungal resistance of biocide‐treated wood flour (WF)/high density polyethylene (HDPE) and bamboo flour (BF)/HDPE composites. The biocides included 4,5‐dichloro‐2‐octyl‐isothiazolone (DCOIT), zinc pyrithione (ZPT), and carbendazim (MBC). Resistance to algae and fungi was evaluated by artificially accelerated tests. Treated and untreated samples were exposed to algae (Chlorella vulgaris, Ulothrix sp., Scenedesmus quadricauda, and Oscillatoria sp.) and fungi (Coriolus versicolor and Poria placenta) for 21 days and 12 weeks, respectively. The volatile components of WF and BF extractives were analyzed by gas chromatography‐mass spectrometry (GC‐MS). The results indicated that incorporation of DCOIT, ZPT, and MBC effectively enhanced the durability of WF/HDPE and BF/HDPE composites against algal and fungal decay. Accordingly, DCOIT, ZPT, and MBC can be used as potential biocides for both WF/HDPE and BF/HDPE composites. GC‐MS analysis suggested that palmitic acid, oleic acid, stigmasta‐3,5‐dien‐7‐one, and vanillin in WF possibly provided some resistance to fungal attack, whereas di (2‐ethylhexyl) phthalate and linoleic acid in BF were responsible for algal resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45148.

Improvement of cyanobacterial-killing biologically derived substances (BDSs) using an ecologically safe and cost-effective naphthoquinone derivative

In previous studies, naphthoquinone (NQ) compounds have been shown to be effective, selective, and ecologically safe algicides for controlling harmful algal blooming species (HABs) or winter bloom species, such as Stephanodiscus hantzschii. However, there are no reports on NQ-based algicides for use with cyanobacterial blooming species. In this study, we developed 31 NQ compounds to investigate algicides for mitigating cyanobacterial blooms. In addition, to better apply these compounds in the field, we reduced the number of production steps to develop a cost-effective algicide. In preliminary testing, we screened NQ compounds that showed the best algicidal activity on target cyanobacteria, including Aphanizomenon, Dolichospermum, Microcystis, Oscillatoria, and Nostoc species. The compound NQ 2-0 showed the highest algicidal activity (90%) at a low concentration (≥1μM) on target algae. These were very limiting algicidal effects of 1µM NQ 2-0 observed against non-target algae, such as diatoms (Stephanodiscus hantzschii, Cyclotella meneghiniana, Synedra acus, and Aulacoseira granulata) or green algae (Cosmarium bioculatum and Scenedesmus quadricauda), and the effect did not exceed 15–25% (except against S. quadricauda). NQ 2-0 (1μM) showed no eco-toxicity, as represented by the survival rates of Pseudokirchneriella subcapitata (100%), Daphnia magna (100%), and Danio rerio (100%). Additionally, a chronic eco-toxicity assessment showed no toxicity toward the survival, growth or reproduction of D. magna. Moreover, NQ 2-0 quickly dissipated from field water samples and had a half-life of approximately 3.2 days. These results suggest that NQ 2-0 could be a selective and ecologically safe algicide to mitigate harmful cyanobacterial blooms.

Effects of CO2 sequestration on lipid and biomass productivity in microalgal biomass production

The study is focused on the technology and manipulation of production strategies for the cultivation of biomass from four strains of microalgae. Species of microalgae studied are: Chlorella vulgaris, Dunaliella, Scenedesmus quadricauda and Synechococcus spp. The effects of the rate and amount of CO2 removal from the atmosphere and sequestration with dissolved oxygen on lipid production from accumulated biomass were studied. Also, the rate of sequestration of both total and dissolved carbon was investigated. Daily measurements of total, organic and inorganic carbon sequestrated, optical densities, proximate analysis and kinetic parameters of the growing and cultivated microalga were monitored and carried out during the two phases of cultivation: dark and light phases. The values of maximum rate of carbon (IV) oxide removed, rmax varied from 11.73mgL−1min−1 to 18.84mgL−1min−1 from Chlorella vulgaris to Synechoccocus spp. Important parameters such as biomass productivity, maximum pH values obtained at cultivation, lipid content of the produced biomass and the hydraulic detection time for all four strains of microalgae were considered and presented in comparison and with their individual and collective effects. The ratios of the rate of CO2 absorption constant and the constant for the CO2 desorption rate (k1/k2) occurred highest in Dunaliella suggesting that with a high uptake of CO2, the algal strain is more effective in CO2 sequestration. The best biomass producer in this study was the C. vulgaris (Xmax=5400mgL−1 and Px=35.1mgLh−1) where biomass productivity is Px and the maximum cellular concentration is Xmax. C. vulgaris has the highest lipids productivity of 27% while Synechoccocus has the least (11.72%). In general, biomass productivity may be inversely related; this fact may be explained by greater metabolic involvement of lipid biosynthesis. This pioneer study may be advanced further to developing models for strategic manipulation and optimisation approach in micro algal biomass cultivation.

Norfloxacin disrupts Daphnia magna-induced colony formation in Scenedesmus quadricauda and facilitates grazing

Environmental pollutants can negatively affect grazer-induced defenses in phytoplankton species and lead to the disruption of phytoplankton-zooplankton relationships. However, it is still not known whether norfloxacin (NOR), a widely used antibiotic, has such effects on plankton systems when released into the environment. Here, we investigated the colony-forming ability of the green alga Scenedesmus quadricauda as well as the behavior (hopping frequency and duration of quiescence) and grazing rate of the cladoceran Daphnia magna, when exposed to different NOR concentrations (0, 50, 500, 5000 and 50,00ugL−1), to determine the effects of NOR on the S. quadricauda-D. magna relationship. Colony size was generally unaffected by NOR but significantly increased when subjected to the stress of adding grazers; however, the combined effects of adding grazers and increasing NOR concentrations led to consistently decreased colony size compared to only adding grazers. The hopping frequency and the time spent on swimming of D. magna individuals decreased while their grazing rate increased with increasing NOR concentrations. Thus, NOR seemed to inhibit grazer-induced colony formation in S. quadricauda, resulting in more algal cells being consumed by grazers, despite inhibiting grazers’ feeding behavior. Considering that phytoplankton-zooplankton interaction plays an important role in determining ecological process of aquatic ecosystems, ecosystem function might be more affected by NOR contamination than previously recognized.

HORIZONTAL TRANSFER OF PLASMID DNA BETWEEN DIFFERENT BACTERIA SPECIES UNDER MICROBIAL INTERACTIONS

Horizontal transfer of plasmid DNA was investigated under phytoplankton metabolites / zooplankton predation exposure condition, to obtain some basic information about the prosperity and decay of GMO (genetically modified microorganisms) in filed release was investigated in this study. Escherichia coli HB101, E.coli C600, E.coli S17-1, Pseudomonas aeruginosa PAO1 (gram-negative) and Bacillus cereusMC (gram-positive) as recipient strain of plasmid DNA, E.coli HB101/pBR325, E.coli C600/RP4 and E.coliS17-1/pSUP104 as donor of plasmid DNA, were supplied. As phytoplankton, Microcystis aeruginosa(cyanophyceae), Melosira varians (bacillariophyceae) and Scenedesmus quadricauda (chlorophyceae) collected from Lake Tega as donor of metabolites, were supplied. As zooplankton, Tetrahymena pyriformis(cilliata) and Philodina erythrophthalma (rotifer) collected from Lake Tega as predator were supplied. The results can be concluded as follows; 1) Phytoplankton metabolites leads acceleration of horizontal transfer between not only same strains but also different strain in spite of whether transmissible or not, 2) Zooplankton predation leads decrease of bacterial individual number and horizontal transfer of plasmid DNA, and 3) Horizontal plasmid DNA transfer is influenced greatly, because the natural ecosystem includes phytoplankton as producer and zooplankton as consumer in the same time.

Antioxidant responses of different microalgal species to nonylphenol-induced oxidative stress

The antioxidant responses of four green microalgae, i.e., Chlorella vulgaris, Chlorella sp., Selenastrum capricornutum and Scenedesmus quadricauda, under control, low (0.1 mg L−1) and high (1.0 mg L−1) nonylphenol (NP) concentration were studied. The antioxidant responses of microalgae to NP depended on both NP concentrations and exposure time. The effects of NP on antioxidant responses were most obvious on the first day of exposure and the effects decreased with prolonged exposure time. At low NP concentration, there were no significant changes in activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), or in glutathione (GSH) content, in all four species, while high concentration of NP led to different changes in these parameters. In NP-tolerant species, i.e., C. vulgaris and Chlorella sp., activities of SOD, CAT and POD increased remarkably when exposed to high NP concentration, while the increase was less evident or insignificant in Se. capricornutum and Sc. quadricauda, the two NP-sensitive species. On the other hand, the malondialdehyde (MDA) content declined gradually with increase in NP concentrations, particularly in C. vulgaris and Chlorella sp. Similarly, NP exposure caused an inhibition of glutathione peroxidase (GPX) activity in all four species. However, the changes of glutathione reductase (GR) and glutathione S-transferase (GST) activity did not seem to correlate with the NP tolerance of microalgae. These results suggested that various antioxidant mechanisms were involved in microalgae when exposed to NP, and the NP-tolerant species displayed more evident and rapid changes in some antioxidant responses than the NP-sensitive ones.

Test procedures for measuring the (sub)chronic effects of chemicals on the freshwater cyclopoid Eucyclops serrulatus

The purpose of this study has been to describe test procedures for measuring the (sub)chronic effects of chemicals on the freshwater cyclopoid Eucyclops serrulatus. To this end we have adapted the setting of the standard full life-cycle protocol of the marine harpacticoid A. tenuiremis to E. serrulatus. We have tested the effects of 4 different diets, two temperatures and two rearing volumes on the survival, development, reproduction and population growth rates of this species. Our results have highlighted that full life-cycle tests can be run using 2 mL-glass vials, a diet consisting of a mixture of living cells of Chlorella sorokiniana and Scenedesmus quadricauda, at either 25 °C (test duration: 42 days) or 18 °C (test duration: 51 days). However, the best performance in terms of survival, development, reproducibility and population growth rates with this species was obtained at 18 °C, albeit with significantly longer test duration. Subchronic tests in 2 mL-glass vials with the mixture microalgal diet at both temperatures are available options if considered appropriate for the objectives of a given study. In particular, developmental tests from nauplius to copepodid may profitably be performed in about 11 days at 18 °C and in 6 days at 25 °C. Under the same test conditions, subchronic tests from copepodid to adult may be run in 19 days at 18 °C and in 16 days at 25 °C.

The formation of haloacetamides, as an emerging class of N-DBPs, from chlor(am)ination of algal organic matter extracted from Microcystis aeruginosa, Scenedesmus quadricauda and Nitzschia palea

The formation of haloacetamides, as an emerging class of N-DBPs, from AOM disinfection extracted from Microcystis aeruginosa, Scenedesmus quadricauda and Nitzschia palea.

Allelopathic effects of Microcystis aeruginosa on green algae and a diatom: Evidence from exudates addition and co-culturing

Allelopathic interactions among phytoplankton species are regarded as one of the important factors contributing to phytoplankton species competition and succession. The role and extent of allelopathic effects of blooming freshwater cyanobacteria on other phytoplankton species in eutrophied waters, however, are still unknown. We examined the allelopathic effect of Microcystis aeruginosa on two common green algae (Scenedesmus quadricauda, Chlorella pyrenoidosa) and a diatom (Cyclotella meneghiniana) by adding exudates from different growth phases and in co-culture tests. Exudates of M. aeruginosa from the exponential growth phase and the stationary phase significantly inhibited the growth of S. quadricauda, C. pyrenoidosa and C. meneghiniana, whereas those from the decline phase increased their growth. The presence of M. aeruginosa extremely inhibited the growth of all tested species in co-cultures within 24h. Our results indicate that under the tested environmental conditions (25°C, light 80μmol quanta m−2s−1, manual shaking twice a day), allelopathic effects of M. aeruginosa on other phytoplankton species can significantly contribute to their competitive success.

Toxicity of aqueous vanadium to zooplankton and phytoplankton species of relevance to the athabasca oil sands region

Vanadium (V) is an abundant trace metal present in bitumen from the Athabasca Oil Sands (AOS) region in Alberta, Canada. The upgrading of bitumen can result in the production of large volumes of a carbonaceous material referred to as petroleum coke that contains V at elevated levels compared to the native bitumen. Previous studies have shown that coke has the capacity to leach ecotoxicologically relevant levels of V into water it contacts, yet limited data are available on the toxicity of aqueous V to planktonic organisms. Therefore, this study set out to evaluate the acute and chronic toxicity of V (as vanadate oxyanions) to freshwater zooplankton and phytoplankton species that are either commonly-used laboratory species, or species more regionally-representative of northern Alberta. Four cladoceran (2-d and 21-d tests) and two algal (3-d tests) species were exposed to V to obtain both acute and chronic toxicity estimates. Acute V toxicity (LC50s) ranged from 0.60mgV/L for Ceriodaphnia quadrangula to 2.17mgV/L for Daphnia pulex. Chronic toxicity estimates (EC50s) for cladoceran survival and reproduction were nearly identical within species and ranged from a low of 0.13 to a high of 0.46mgV/L for Daphnia dentifera and D. pulex, respectively. The lack of sublethal V toxicity in daphnia suggests a direct mechanism of toxicity through ion imbalance. Growth inhibition (EC50) of green algae occurred at concentrations of 3.24 and 4.12mgV/L for Pseudokirchneriella subcapitata and Scenedesmus quadricauda, respectively. Overall, cladocerans were more sensitive to V than green algae, with survival of the field-collected D. dentifera being approximately 2.5 to 3.5 times more sensitive to acute and chronic V exposure than the standard test species D. pulex. However, there were no significant differences in V toxicity between the field-collected cladocerans Simocephalus serrulatus and C. quadrangula, compared to the respective standard species D. pulex and Ceriodaphnia dubia. Similarly, there were no significant differences in sensitivity to V in the two algal species evaluated. Based on V concentrations reported in laboratory-generated coke leachates, zooplankton survival could be adversely impacted under conditions of chronic leachate exposure if V concentrations in the environment exceed 0.1mg/L. Furthermore, toxicity thresholds from commonly-used planktonic test species would likely have sufficed for derivation of a V water quality guideline (WQG) for protection of local aquatic communities near oil sands operations, but the new data presented here on V toxicity to more regionally-representative species will strengthen the database for WQG derivation.

Green microalgae in removal and biotransformation of estradiol and ethinylestradiol

Estrogens, a group of steroid hormones, are serious environmental pollutants due to their persistence, ubiquity, and endocrine-disrupting toxicity. Natural and synthetic estrogens, such as 17β-estradiol (E2) and 17α-ethinylestradiol (EE2), respectively, have been found in the influent of municipal wastewater treatment plants. The removal and biotransformation of mixed or single E2 and EE2 by six microalgal species, including three local isolates of Chlamydomonas sp. (WW), Chlorella sp. (2f5aia), and Chlorella sp. (1uoai) and three commercially available species, namely Scenedesmus quadricauda (= Desmodesmus communis) (SQ), Selenastrum capricornutum (SC), and Chlorella vulgaris (CV), were compared. The biological removal of estrogen was incubation time- and species-dependent. Among six species, SC had the highest removal ability for both E2 and EE2; their removal increased with incubation time and achieved 93.9 and 75.3 % removal, respectively, at the end of incubation. After 7-day incubation, the removal percentage of mixed EE2 by SC was significantly higher than that of single EE2 (P ≤ 0.05). Differences in the removal percentages of E2 and EE2 between commercial and local species were not significant, as reflected by the comparable removal efficiency among three Chlorella species, CV, 1uoai, and 2f5aia, with the highest removal of E2, either in mixed or in single treatment, at day 2. In all species, the percentages of E2 or EE2 taken up into cells were very low (0.2–9.6 %) when compared to the respective biological removal percentages. E2 was easily transformed into estrone (E1) and some unknown products by all microalgal species, while the products for EE2 transformation could not be identified due to the limited availability of the standards for metabolites.

Comparative transcriptomics reveals molecular components associated with differential lipid accumulation between microalgal sp., Scenedesmus dimorphus and Scenedesmus quadricauda

Scenedesmus is considered as a potential oil-producing green microalgae having higher lipid content with suitable fatty acid profile (high oleic acid) for biodiesel production. Comparative transcriptome analysis of two Scenedesmus sp., viz. Scenedesmus dimorphus (26%) and Scenedesmus quadricauda (14%) having equivalent biomass and variable lipid content was performed to uncover molecular mechanisms controlling differential lipid production. 76,969 and 40,979 CDSs were predicted from the transcriptomes of S. dimorphus and S. quadricauda respectively, which were subsequently mapped to metabolic pathways. Overall up-regulation of metabolic pathways contributing precursors to storage lipid biosynthesis was observed in S. dimorphus. Glyceraldehyde 3-phosphate dehydrogenase, enolase, acetyl-CoA synthetase, pyruvate dehydrogenase, ATP citrate lyase, glycerol kinase, citrate synthase were identified as major regulators of high lipid content in S. dimorphus. Further, WRINKLED1 transcription factor significantly correlated with high lipid accumulation as revealed by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) in three growth stages of two species. This study provides a broad view of storage lipid production in Scenedesmus species with potential implications in designing suitable genetic interventions towards increase in lipid content vis-à-vis central carbon metabolism.

Stimulatory effect of auxins on the growth and lipid productivity of Chlorella pyrenoidosa and Scenedesmus quadricauda

This study investigated the impact of various auxins on microalgal growth and cellular composition. Two freshwater algae, i.e., Chlorella pyrenoidosa and Scenedesmus quadricauda were used. Results were analyzed using principal component analysis (PCA) and canonical correspondence analysis (CCA). The stimulatory effect of auxins on lipid content and lipid production was found to be as follows: indole-3-propionic acid (IPA)>indole-3-acetic acid (IAA)>indole-3-butyric acid (IBA)>naphthalene acetic acid (NAA). This is the first report of an increased stimulatory effect of IPA on microalgae that differs from previous study. A concentration of 60mgL−1 IPA caused the maximum growth rate, which increased 3 fold compared to the control. Lipid productivity in the samples treated with auxins was generally higher than the controls, and reached 4 fold higher with the addition of IPA. Using PCA, this study provided evidence that IBA and NAA show similar stimulatory effects on cellular composition. The increase in biomass and lipid productivity demonstrates the potential application of plant hormones for improving microalgae growth in commercial-scale cultivation and thus reducing the cost of biofuel production.

Flocculation and mechanism of self-flocculating lipid producer microalga Scenedesmus quadricauda for biomass harvesting

In this study, the extracellular polymeric substance of Scenedesmus quadricauda called EPS-S.q and its bioflocculatoin mechanism were investigated. Results showed EPS-S.q was successfully used as bioflocculating agent for S. quadricauda biomass harvesting and flocculation efficiency of up to 86.7% to S. quadricauda cells could be achieved in presence of Zn2+. EPS-S.q was the flocculating agent for self-flocculating microalga S. quadricauda and bioflocculation mechanism was polymer bridging. The sugar and protein mass fraction of dry EPS-S.q was sugar 56.7% and protein 41%. The infrared spectrum further indicated the presence of hydroxyl, carboxyl and amino groups. Moreover, pH decrease induced the flocculation of S. quadricauda and 78.4% of flocculation efficiency was the highest at pH 3. In addition, chemical flocculant FeCl3 was efficiently used for S. quadricauda harvesting and up to 96.8% of flocculation efficiency could be achieved for S. quadricauda culture with biomass concentration 0.21–0.39 g L−1 at pH 7.

Cultivating Chlorella vulgaris and Scenedesmus quadricauda microalgae to degrade inorganic compounds and pesticides in water.

This work evaluates the possibility of cultivating Scenedesmus quadricauda and Chlorella vulgaris microalgae in wastewater from the hydroponic cultivation of tomatoes with the aim of purifying the water. S. quadricauda and C. vulgaris were also used in purification tests carried out on water contaminated by the following active ingredients: metalaxyl, pyrimethanil, fenhexamid, iprodione, and triclopyr. Fifty-six days after the inoculum was placed, a reduction was found in the concentration of nitric nitrogen, ammonia nitrogen, and soluble and total phosphorus. The decrease was 99, 83, 94, and 94%, respectively, for C. vulgaris and 99, 5, 88, and 89%, respectively, for S. quadricauda. When the microalgae were present, all the agrochemicals tested were removed more quickly from the water than from the sterile control (BG11). The increase in the rate of degradation was in the order metalaxyl>fenhexamid>iprodione>triclopyr>pyrimethanil. It was demonstrated that there was a real degradation of fenhexamid, metalaxyl, triclopyr, and iprodione, while in the case of pyrimethanil, the active ingredient removed from the substrate was absorbed onto the cells of the microalgae. It was also found that the agrochemicals used in the tests had no significant effect on the growth of the two microalgae. The experiment highlighted the possibility of using cultivations of C. vulgaris and S. quadricauda as purification systems for agricultural wastewater which contains eutrophic inorganic compounds such as nitrates and phosphates and also different types of pesticides.