Continuous UV-C/H2O2 and UV-C/Chlorine applied to municipal secondary effluent and nanofiltration retentate: Removal of contaminants of emerging concern, ecotoxicity, and reuse potential.

As global effects of water scarcity raise concerns and environmental regulations evolve, contemporary wastewater treatment plants (WWTPs) face the challenge of effectively removing a diverse range of contaminants of emerging concern (CECs) from municipal effluents. This study focuses on the assessment of advanced oxidation processes (AOPs), specifically UV-C/H2O2 and UV-C/Chlorine, for the removal of 14 target CECs in municipal secondary effluent (MSE, spiked with 10 µg L-1 of each CEC) or in the subsequent MSE nanofiltration retentate (NFR, no spiking). Phototreatments were carried out in continuous mode operation, with a hydraulic retention time of 3.4 min, using a tube-in-tube membrane photoreactor. For both wastewater matrices, UV-C photolysis (3.3 kJ L-1) exhibited high efficacy in removing CECs susceptible to photolysis, although lower treatment performance was observed for NFR. In MSE, adding 10 mg L-1 of H2O2 or Cl2 enhanced treatment efficiency, with UV-C/H2O2 outperforming UV-C/Chlorine. Both UV-C/AOPs eliminated the chronic toxicity of MSE toward Chlorella vulgaris. In the NFR, not only was the degradation of target CECs diminished, but chronic toxicity to C. vulgaris persisted after both UV-C/AOPs, with UV-C/Chlorine increasing toxicity due to potential toxic by-products. Nanofiltration permeate (NFP) exhibited low CECs and microbial content. A single chlorine addition effectively controlled Escherichia coli regrowth for 3 days, proving NFP potential for safe reuse in crop irrigation (<1 CFU/100 mL for E. coli; <1 mg L-1 for free chlorine). These findings provide valuable insights into the applications and limitations of UV-C/H2O2 and UV-C/Chlorine for distinct wastewater treatment scenarios.

Microcystin-LR (MC-LR) inhibits green algae growth by regulating antioxidant and photosynthetic systems.

Microcystins release from bloom-forming cyanobacteria is considered a way to gain competitive advantage in Microcystis populations, which threaten water resources security and aquatic ecological balance. However, the effects of microcystins on microalgae are still largely unclear. Through simulated culture experiments and the use of UHPLC-MS-based metabolomics, the effects of two microcystin-LR (MC-LR) concentrations (400 and 1,600 µg/L) on the growth and antioxidant properties of three algae species, the toxic Microcystis aeruginosa, a non-toxic Microcystis sp., and Chlorella vulgaris, were studied. The MC-LR caused damage to the photosynthetic system and activated the protective mechanism of the photosynthetic system by decreasing the chlorophyll-a and carotenoid concentrations. Microcystins triggered oxidative stress in C. vulgaris, which was the most sensitive algae species studied, and secreted more glycolipids into the extracellular compartment, thereby destroying its cell structure. However, C. vulgaris eliminated reactive oxygen species (ROS) by secreting terpenoids, thereby resisting oxidative stress. In addition, two metabolic pathways, the vitamin B6 and the sphingolipid pathways, of C. vulgaris were significantly disturbed by microcystins, contributing to cell membrane and mitochondrial damage. Thus, both the low (400 µg/L) and the high (1,600 µg/L) MC-LR concentration inhibited algae growth within 3 to 7 days, and the inhibition rates increased with the increase in the MC-LR concentration. The above results indicate that the toxin-producing Microcystis species have a stronger toxin tolerance under longer-term toxin exposure in natural water environments. Thus, microcystins participates in interspecific interaction and phytoplankton population regulation and creates suitable conditions for the toxin-producing M. aeruginosa to become the dominant species in algae blooms.

Formation and toxicity alteration of halonitromethanes from Chlorella vulgaris during UV/chloramination process involving bromide ion.

Frequent algal blooms cause algal cells and their algal organic matter (AOM) to become critical precursors of disinfection by-products (DBPs) during water treatment. The presence of bromide ion (Br-) in water has been demonstrated to affect the formation laws and species distribution of DBPs. However, few researchers have addressed the formation and toxicity alteration of halonitromethanes (HNMs) from algae during disinfection in the presence of Br-. Therefore, in this work, Chlorella vulgaris was selected as a representative algal precursor to investigate the formation and toxicity alteration of HNMs during UV/chloramination involving Br-. The results showed that the formation concentration of HNMs increased and then decreased during UV/chloramination. The intracellular organic matter of Chlorella vulgaris was more susceptible to form HNMs than the extracellular organic matter. When the Br-: Cl2 mass ratio was raised from 0.004 to 0.08, the peak of HNMs total concentration increased 33.99%, and the cytotoxicity index and genotoxicity index of HNMs increased 67.94% and 22.80%. Besides, the formation concentration and toxicity of HNMs increased with increasing Chlorella vulgaris concentration but decreased with increasing solution pH. Possible formation pathways of HNMs from Chlorella vulgaris during UV/chloramination involving Br- were proposed based on the alteration of nitrogen species and fluorescence spectrum analysis. Furthermore, the formation laws of HNMs from Chlorella vulgaris in real water samples were similar to those in deionized water samples. This study contributes to a better comprehension of HNMs formation from Chlorella vulgaris and provides valuable information for water managers to reduce hazards associated with the formation of HNMs.

Enhancing the biodiesel production in the green alga Chlorella vulgaris by heavy metal stress and prediction of fuel properties from fatty acid profiles.

The green microalga Chlorella vulgaris was used as a test organism during this study for evaluation of the impact of different heavy metal stress, Mn2+, Co2+, and Zn2+, on enhancing the biodiesel production. The algal cultures were grown for 13 days under heavy metal stress after which were subjected to estimation of growth, some primary metabolites, lipid, and fatty acid profiles. The maximum lipid accumulation (283.30 mg/g CDW) was recorded in the algal culture treated with 3 µM cobalt nitrate. Application of 2 mM manganese chloride; 1, 2, and 3 µM cobalt nitrate; and 0.2, 0.4, and 0.6 mM zinc sulfate caused highly significant increases in the lipid contents amounting to 183.8, 191.4, 230.6, 283.3, 176.3, 226.0, and 212.1 mg/g CDW, respectively, in comparison to control (153.4 mg/g CDW). The maximum proportion of saturated fatty acids (SFA) (64.44%) was noted in the culture treated with 6 mM MnCl2 due to the existence of palmitic acid (C16:0), stearic acid (C18:0), and pentadecylic acid (C15:0) which are represented by 53.59%, 5.96%, and 1.37%, respectively, of the total FAs. Relative increase in energy compound (REEC) showed that 1, 2, and 3 µM Co2+ lead to the highest stimulation in lipid and carbohydrate contents to 0.207, 0.352, and 0.329 × 103%, respectively. Empirical formulas were used for the assessment of biodiesel fuel properties based on FAME composition. The estimated properties met the prescribed international standard criteria.

Presence of humic acid in the environment holds promise as a potential mitigating factor for the joint toxicity of polystyrene nanoplastics and herbicide atrazine to Chlorella vulgaris: 96-H acute toxicity.

Increasing amounts of amino-functionalized polystyrene nanoplastics (PS-NH2) are entering aquatic ecosystems, raising concerns. Hence, this study investigated 96-h acute toxicity of PS-NH2 and its combination with the pesticide atrazine (ATZ) in the absence/presence of humic acid (HA) on the microalgae Chlorella vulgaris (C. vulgaris). Results showed that both PS-NH2 and PS-NH2+ATZ reduced algal growth, photosynthetic pigments, protein content, and antioxidant capacity, while increasing enzymatic activities. Gene expression related to oxidative stress was altered in C. vulgaris exposed to these treatments. Morphological and intracellular changes were also observed. The combined toxicity of PS-NH2+ATZ demonstrated a synergistic effect, but the addition of environmentally relevant concentration of HA significantly alleviated its toxicity to C. vulgaris, indicating an antagonistic effect due to the emergence of an eco-corona, and entrapment and sedimentation of PS-NH2+ATZ particles by HA. This study firstly highlights the role of HA in mitigating the toxicity of PS-NH2 when combined with other harmful compounds, enhancing our understanding of HA's presence in the environment.

Prediction of acute toxicity for Chlorella vulgaris caused by tire wear particle-derived compounds using quantitative structure-activity relationship models.

Tire wear particles (TWPs) enter aquatic ecosystems through various pathways, such as rainwater and urban runoff. Additives in TWPs can harm aquatic organisms in these ecosystems. Therefore, it is essential to investigate their toxicity to aquatic organisms. In our study, we initially recorded the median effective concentrations of 21 TWP-derived compounds on Chlorella vulgaris growth, ranging from 0.04 to 8.60 mg/L. Subsequently, through an extensive review of the literature, we incorporated 112 compounds with specific toxicity endpoints to construct the QSAR model using genetic algorithm and multiple linear regression techniques, followed by the construction of the consensus model and the quantitative read-across structure-activity relationship (q-RASAR) model. Meanwhile, we employed rigorous internal and external validation measures to assess the performance of the model. The results indicated that the developed q-RASAR model exhibited strong adaptation, robustness, and reliable prediction, with q-RASAR indicators of Q2LOO = 0.7673, R2tr = 0.8079, R2test = 0.8610, Q2Fn = 0.8285-0.8614, and CCCtest = 0.9222. Based on an external dataset containing 128 emerging TWP-derived compounds, the model's applicability domain coverage was 90.6 %. The q-RASAR model predicted that the structure of diphenylamine was associated with higher toxicity, possibly liked to the SpMax2_Bhm and LogBCF descriptors. The established model reliably provides prediction and fills a critical data gap. These findings highlight the potential risks posed by emerging TWP-derived compounds to aquatic organisms.

Combined toxic effects of polystyrene nanoplastics and lead on Chlorella vulgaris growth, membrane lipid peroxidation, antioxidant capacity, and morphological alterations.

In recent years, there has been a significant rise in the utilization of amino-functionalized polystyrene nanoplastics (PS-NH2). This surge in usage can be attributed to their exceptional characteristics, including a substantial specific surface area, high energy, and strong reactivity. These properties make them highly suitable for a wide range of industrial and medical applications. Nevertheless, there is a growing apprehension regarding their potential toxicity to aquatic organisms, particularly when considering the potential impact of heavy metals like lead (Pb) on the toxicity of PS-NH2. Herein, we examined the toxic effects of sole PS-NH2 (90 nm) at five concentrations (e.g., 0, 0.125, 0.25, 0.5, and 1 mg/L), as well as the simultaneous exposure of PS-NH2 and Pb2+ (using two environmental concentrations, e.g., 20 µg/L for Pb low (PbL) and 80 µg/L for Pb higher (PbH)) to the microalga Chlorella vulgaris. After a 96-h exposure, significant differences in chlorophyll a content and algal growth (biomass) were observed between the control group and other treatments (ANOVA, p < 0.05). The algae exposed to PS-NH2, PS-NH2 + PbL, and PS-NH2 + PbH treatment groups exhibited dose-dependent toxicity responses to chlorophyll a content and biomass. According to the Abbott toxicity model, the combined toxicity of treatment groups of PS-NH2 and PbL,H showed synergistic effects. The largest morphological changes such as C. vulgaris' size reduction and cellular aggregation were evident in the medium treated with elevated concentrations of both PS-NH2 and Pb2+. The toxicity of the treatment groups followed the sequence PS-NH2 < PS-NH2 + PbL < PS-NH2 + PbH. These results contribute novel insights into co-exposure toxicity to PS-NH2 and Pb2+ in algae communities.

Impact of organic matter molecular weight on hexavalent chromium enrichment in green microalgae.

In lightly polluted water containing heavy metals, organic matter, and green microalgae, the molecular weight of organic matter may influence both the growth of green microalgae and the concentration of heavy metals. This study elucidates the effects and mechanisms by which different molecular weight fractions of fulvic acid (FA), a model dissolved organic matter component, facilitate the bioaccumulation of hexavalent chromium (Cr(VI)) in a typical green alga, Chlorella vulgaris. Findings show that the addition of FA fractions with molecular weights greater than 10 kDa significantly enhances the enrichment of total chromium and Cr(VI) in algal cells, reaching 21.58%-31.09 % and 16.17 %-22.63 %, respectively. Conversely, the efficiency of chromium enrichment in algal cells was found to decrease with decreasing molecular weight of FA. FA molecular weight within the range of 0.22 µm-30 kDa facilitated chromium enrichment primarily through the algal organic matter (AOM) pathway, with minor contributions from the algal cell proliferation and extracellular polymeric substances (EPS) pathways. However, with decreasing FA molecular weight, the AOM and EPS pathways become less prominent, whereas the algal cell proliferation pathway becomes dominant. These findings provide new insights into the mechanism of chromium enrichment in green algae enhanced by medium molecular weight FA.

Alleviating binary toxicity of polystyrene nanoplastics and atrazine to Chlorella vulgaris through humic acid interaction: Long-term toxicity using environmentally relevant concentrations.

In this study, microalgae Chlorella vulgaris (C. vulgaris) were simultaneously exposed to environmental concentrations of amino-functionalized polystyrene nanoplastics (PS-NH2; 0.05, 0.1, 0.2, 0.3 and 0.4 mg/L) and the world's second most used pesticide, the herbicide atrazine (ATZ; 10 µg/L), in the absence and presence of humic acid (HA; 1 mg/L) for 21 days. Due to the low concentrations of PS-NH2, the majority of them could not cause a significant difference in the end-points of biomass, chlorophylls a and b, total antioxidant, total protein, and superoxide dismutase and malondialdehyde compared to the control group (p > 0.05). On the other hand, by adding ATZ to the PS-NH2, all the mentioned end-point values showed a considerable difference from the control (p < 0.05). The exposure of PS-NH2+ATZ treatments to the HA could remarkably reduce their toxicity, additionally, HA was able to decrease the changes in the expression of genes related to oxidative stress (e.g., superoxide dismutase, glutathione reductase, and catalase) in the C. vulgaris in the most toxic treatment group (e.g., PS-NH2+ATZ). The synergistic toxicity of the PS-NH2+ATZ group could be due to their enhanced bioavailability for algal cells. Nevertheless, the toxicity alleviation in the PS-NH2+ATZ treatment group after the addition of HA could be due to the eco-corona formation, and changes in their zeta potential from positive to negative value, which would increase their electrostatic repulsion with the C. vulgaris cells, in such a way that HA also caused a decrease in the formation of C. vulgaris-NPs hetero-aggregates. This research underscores the complex interplay between PS-NH2, ATZ, and HA in aquatic environments and their collective impact on microalgal communities.

Concentration-dependent effects of spinetoram on nontarget freshwater microalgae: A comparative study on Chlorella vulgaris and Microcystis aeruginosa.

The rising global demand for agricultural products is leading to the widespread application of pesticides, such as spinetoram, resulting in environmental pollution and ecotoxicity to nontarget organisms in aquatic ecosystems. This research focused on assessing the toxicity of spinetoram at various concentrations (0, 0.01, 0.1, 0.5, 1.0, and 3.0 mg L-1) on two common freshwater microalgae, Chlorella vulgaris and Microcystis aeruginosa, to shed light on the ecotoxicological effects of insecticides. Our findings demonstrate that M. aeruginosa is more sensitive to spinetoram than is C. vulgaris, with a concentration-dependent reduction in the growth rate observed for M. aeruginosa, whereas only the highest concentration of spinetoram adversely affected C. vulgaris. At a concentration of 0.01 mg L-1, the growth rate of M. aeruginosa unexpectedly increased beginning on day 7, indicating a potential hormetic effect. Although initial exposure to spinetoram improved the photosynthetic efficiency of both microalgae strains at all concentrations, detrimental effects became apparent at higher concentrations and with prolonged exposure. The photosynthetic efficiency of C. vulgaris recovered, in contrast to that of M. aeruginosa, which exhibited limited recovery. Spinetoram more significantly inhibited the effective quantum yield of PSII (EQY) in M. aeruginosa than in C. vulgaris. Although spinetoram is not designed to target phytoplankton, its toxicity can disrupt primary productivity and modify phytoplankton-consumer interactions via bottom-up control mechanisms. This study enhances our understanding of spinetoram's ecotoxicity and potential effects on aquatic ecosystems.

Microplastics leachate may play a more important role than microplastics in inhibiting microalga Chlorella vulgaris growth at cellular and molecular levels.

The leaching of microplastics (MPs) additives and their negative effects on aquatic organisms remain to be systematically elucidated. In this study, the toxicological effects of MPs leachate (micro-sized polyethylene (mPE) and micro-sized polyvinyl chloride (mPVC) acceleratedly leached by UVA for 15, 90, and 180 days in seawater) on microalga Chlorella vulgaris in terms of cell growth inhibition, oxidative stress, and transcriptomes were investigated. The leachate components of MPs aged for 90 days were further identified to elucidate the corresponding toxicity mechanisms of MPs on microalgal cells. The results revealed that both leachates of mPE and mPVC inhibited cell growth and increased oxidative stress in C. vulgaris, accompanied by a growth inhibition rate to microalgal cells of 4.0%-36.2% and 7.1%-48.2%, respectively. At the same mass concentration, the toxicological effects on C. vulgaris followed the order of mPVC leachate > mPE > mPE leachate > mPVC, whereas MPs leaching time indicated no change in MPs leaching toxicity. Furthermore, the gene functions of "translation, ribosomal structure and biogenesis" were mostly affected by MPs leachate. Compared to mPE leachate and pure MPs, the stronger inhibitory effects of mPVC leachate on microalgal cells may be attributed to the fact that more substances were leached from the polymer of mPVC, including Zn, farnesol isomer a, 2,6-di-tert-butyl-4-methylphenol, and acetyl castor oil methyl ester. In summary, this study provides a better understanding of the ecotoxicological influences of MPs and MPs leachate, and offers a warning on the ecological risk caused by plastic additives.

Simulating the Interplay between the Uptake of Inorganic Phosphate and the Cell Phosphate Metabolism under Phosphorus Feast and Famine Conditions in Chlorella vulgaris.

Using a mathematical simulation approach, we studied the dynamics of the green microalga Chlorella vulgaris phosphate metabolism response to shortage and subsequent replenishing of inorganic phosphate in the medium. A three-pool interaction model was used to describe the phosphate uptake from the medium, its incorporation into the cell organic compounds, its storage in the form of polyphosphates, and culture growth. The model comprises a system of ordinary differential equations. The distribution of phosphorous between cell pools was examined for three different stages of the experiment: growth in phosphate-rich medium, incubation in phosphate-free medium, and phosphate addition to the phosphorus-starving culture. Mathematical modeling offers two possible scenarios for the appearance of the peak of polyphosphates (PolyP). The first scenario explains the accumulation of PolyP by activation of the processes of its synthesis, and the decline in PolyP is due to its redistribution between dividing cells during growth. The second scenario includes a hysteretic mechanism for the regulation of PolyP hydrolysis, depending on the intracellular content of inorganic phosphate. The new model of the dynamics of P pools in the cell allows one to better understand the phenomena taking place during P starvation and re-feeding of the P-starved microalgal cultures with inorganic phosphate such as transient PolyP accumulation. Biotechnological implications of the observed dynamics of the polyphosphate pool of the microalgal cell are considered. An approach enhancing the microalgae-based wastewater treatment method based on these scenarios is proposed.

One-pot fabrication of Ag @Ag2O core-shell nanostructures for biosafe antimicrobial and antibiofilm applications.

Microbial contamination is one of the major dreadful problems that raises hospitalization, morbidity and mortality rates globally, which subsequently obstructs socio-economic progress. The continuous misuse and overutilization of antibiotics participate mainly in the emergence of microbial resistance. To circumvent such a multidrug-resistance phenomenon, well-defined nanocomposite structures have recently been employed. In the current study, a facile, novel and cost-effective approach was applied to synthesize Ag@Ag2O core-shell nanocomposites (NCs) via chemical method. Several techniques were used to determine the structural, morphological, and optical characteristics of the as-prepared NCs. XRD, Raman, FTIR, XPS and SAED analysis revealed a crystalline hybrid structure of Ag core and Ag2O shell. Besides, SEM and HRTEM micrographs depicted spherical nanoparticles with size range of 19-60 nm. Additionally, zeta potential and fluorescence spectra illustrated aggregated nature of Ag@Ag2O NCs by - 5.34 mV with fluorescence emission peak at 498 nm. Ag@Ag2O NCs exhibited higher antimicrobial, antibiofilm, and algicidal activity in dose-dependent behavior. Interestingly, a remarkable mycocidal potency by 50 µg of Ag@Ag2O NCs against Candida albican; implying promising activity against COVID-19 white fungal post-infections. Through assessing cytotoxicity, Ag@Ag2O NCs exhibited higher safety against Vero cells than bulk silver nitrate by more than 100-fold.

Aged microplastics decrease the bioavailability of coexisting heavy metals to microalga Chlorella vulgaris.

Environmental aging of ubiquitous microplastics (MP) occurs through the action of biotic and abiotic factors, and aged MP exhibit different physicochemical properties and environmental behavior from virgin MP. This study aimed to investigate the aged micro-sized polystyrene (mPS) and polyvinyl chloride (mPVC), and the heavy metals copper (Cu) and cadmium (Cd), and examine the effects of their combined toxicities on microalga Chlorella vulgaris. Results showed that the presence of MP inhibited cell growth as compared with the control, the inhibition rate (I) decreased as concentrations of MP rose and aged MP exhibited stronger inhibition of cells than did virgin MP. The largest I was achieved in each culture with the MP concentration of 0.01 g/L, in which aged mPS with the maximal of 36.84% (Iaged mPS) followed by aged mPVC (Iaged mPVC = 30.03%), virgin mPS (Ivirgin mPS = 29.10%) and virgin mPVC (Ivirgin mPVC = 16.72%). Addition of the heavy metals Cu2+ and Cd2+ significantly inhibited cell growth, and toxicity increased with concentrations in a range of 0.5-2.0 mg/L; the maximum I values were 19.50% (ICu) and 85.14% (ICd), respectively. The combined toxicity of aged MP + Cu or aged MP + Cd was less than that of individual heavy metals. In particular, as compared with the maximal ICd of 85.14% achieved by single Cd2+, the toxicity of Cd2+ was greatly reduced when combined with aged mPS and mPVC, with the I value decreased to 27.55% (Iaged mPS) and 32.51% (Iaged mPVC), respectively. Both single and combined treatments caused cell damage to the microalga, accompanied by increased superoxide dismutase (SOD) and intracellular malonaldehyde (MDA) content.

Acute toxicity and ecological risk assessment of 4,4'-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone and 4-MBC in ultraviolet (UV)-filters.

Ultraviolet (UV) filters are used in cosmetics, personal care products and packaging materials to provide sun protection for human skin and other substances. Little is known about these substances, but they continue to be released into the environment. The acute toxicity of 4,4'-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone and 4-MBC to Chlorella vulgaris and Daphnia magna were analyzed in this study. The 96 h-EC50 values of 4,4'-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone and 4-MBC on C. vulgaris were 183.60, 3.50 and 0.16874 mg/L, respectively. The 48 h-LC50 of 4,4'-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone and 4-MBC on D. magna were 12.50, 3.74 and 0.54445 mg/L, respectively. The toxicity of a mixture of 4,4'-dihydroxybenzophenone and 4-MBC showed addictive effect on C. vulgaris, while the toxicity of mixtures of 4,4'-dihydroxybenzophenone and 2,4,4'-trihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone and 4-MBC as well as 4,4'-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone and 4-MBC all showed antagonistic effect on C. vulgaris. The induced no-effect concentrations of 4,4'-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone and 4-MBC by the assessment factor (AF) method were 0.0125, 0.00350 and 0.000169 mg/L, respectively.

Synthesis, characterization and investigation of algal oxidative effects of water-soluble copper phthalocyanine containing sulfonate groups.

In this study, the chemical and algicidal properties of the newly synthesized compound (2) were evaluated and its algal oxidative effects were determined in Arthrospira platensis and Chlorella vulgaris. First, we have reported on the synthesis and characterization of highly water-soluble copper (II) phthalocyanine (2), containing sodium 2-mercaptoethanesulfonate (2) substituents at the peripheral positions. Some spectroscopic techniques were used to characterize the new synthesized compound (2). In terms of biological properties, C. vulgaris were more tolerance to compound (2) than A. platensis depending to growth parameters. When SOD (Superoxide dismutase) activity significantly increased at 0.25 ppb and 1.5 ppb concentrations in A. platensis cultures, it increased at 6 ppb concentration in C. vulgaris cultures. GR (Glutathione reductase) activity decreased at 1 ppb and 1.5 ppb concentrations while APX (Ascorbate peroxidase) activity did not show a significant change at any concentrations in A. platensis cultures. GR activity showed a significant increase at 6 ppb concentration, while APX activity increased at all concentrations compared to control in C. vulgaris cultures. MDA (malondialdehyde) and H2O2 content decreased at 1 and 1.5 ppb concentrations but there were significant increases in the proline content at all concentrations compared to the control in A. platensis. MDA, H2O2 and free proline contents showed a significant increase at 0.5 ppb concentration in C. vulgaris. In conclusion, compound (2) have algicidal effects, and also it causes to oxidative stress in these organisms.

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.

Lipid accumulation patterns and role of different fatty acid types towards mitigating salinity fluctuations in Chlorella vulgaris.

Mangrove-dwelling microalgae are well adapted to frequent encounters of salinity fluctuations across their various growth phases but are lesser studied. The current study explored the adaptive changes (in terms of biomass, oil content and fatty acid composition) of mangrove-isolated C. vulgaris UMT-M1 cultured under different salinity levels (5, 10, 15, 20, 30 ppt). The highest total oil content was recorded in cultures at 15 ppt salinity (63.5% of dry weight) with uncompromised biomass productivity, thus highlighting the 'trigger-threshold' for oil accumulation in C. vulgaris UMT-M1. Subsequently, C. vulgaris UMT-M1 was further assessed across different growth phases under 15 ppt. The various short, medium and long-chain fatty acids (particularly C20:0), coupled with a high level of C18:3n3 PUFA reported at early exponential phase represents their physiological importance during rapid cell growth. Accumulation of C18:1 and C18:2 at stationary growth phase across all salinities was seen as cells accumulating substrate for C18:3n3 should the cells anticipate a move from stationary phase into new growth phase. This study sheds some light on the possibility of 'triggered' oil accumulation with uninterrupted growth and the participation of various fatty acid types upon salinity mitigation in a mangrove-dwelling microalgae.

Kinetics Growth and Recovery of Valuable Nutrients from Selangor Peat Swamp and Pristine Forest Soils Using Different Extraction Methods as Potential Microalgae Growth Enhancers.

Soil extracts are useful nutrients to enhance the growth of microalgae. Therefore, the present study attempts for the use of virgin soils from Peninsular Malaysia as growth enhancer. Soils collected from Raja Musa Forest Reserve (RMFR) and Ayer Hitam Forest Reserve (AHFR) were treated using different extraction methods. The total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), and dissolved organic carbon (DOC) concentrations in the autoclave methods were relatively higher than natural extraction with up to 132.0 mg N/L, 10.7 mg P/L, and 2629 mg C/L, respectively for RMFR. The results of TDN, TDP, and DOC suggested that the best extraction methods are autoclaved at 121 °C twice with increasing 87%, 84%, and 95%, respectively. Chlorella vulgaris TRG 4C dominated the growth at 121 °C twice extraction method in the RMRF and AHRF samples, with increasing 54.3% and 14%, respectively. The specific growth rate (µ) of both microalgae were relatively higher, 0.23 d-1 in the Ayer Hitam Soil. This extract served well as a microalgal growth promoter, reducing the cost and the needs for synthetic medium. Mass production of microalgae as aquatic feed will be attempted eventually. The high recovery rate of nutrients has a huge potential to serve as a growth promoter for microalgae.

Cochliomycin G, a 14-membered resorcylic acid lactone from a marine-derived fungus Cochliobolus lunatus.

Cochliomycin G (1), a new 14-membered resorcylic acid lactone, together with six known analogues (2-7), was isolated from the culture broth of a marine-derived fungus Cochliobolus lunatus. The planar structure of 1 was established by extensive NMR spectroscopy, and the absolute configuration was elucidated by the combination of empirical rules, CD data, and 13C chemical shift calculations. Compound 1 exhibited potent antifouling activity against Chlorella vulgaris, Chaetoceros socialis, and Navicula exigua, with EC50 values of 1.09, 0.92, and 0.61 µg/mL, respectively.