Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.197
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Agric Food Chem ; 68(6): 1654-1665, 2020 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-31935099

RESUMO

Microalgae accumulate bioavailable selenium-containing amino acids (Se-AAs), and these are useful as a food supplement. While this accumulation has been studied in phototrophic algal cultures, little data exists for heterotrophic cultures. We have determined the Se-AAs content, selenium/sulfur (Se/S) substitution rates, and overall Se accumulation balance in photo- and heterotrophic Chlorella cultures. Laboratory trials revealed that heterotrophic cultures tolerate Se doses ∼8-fold higher compared to phototrophic cultures, resulting in a ∼2-3-fold higher Se-AAs content. In large-scale experiments, both cultivation regimes provided comparable Se-AAs content. Outdoor phototrophic cultures accumulated up to 400 µg g-1 of total Se-AAs and exhibited a high level of Se/S substitution (5-10%) with 30-60% organic/total Se embedded in the biomass. A slightly higher content of Se-AAs and ratio of Se/S substitution was obtained for a heterotrophic culture in pilot-scale fermentors. The data presented here shows that heterotrophic Chlorella cultures provide an alternative for Se-enriched biomass production and provides information on Se-AAs content and speciation in different cultivation regimes.


Assuntos
Aminoácidos/metabolismo , Chlorella/metabolismo , Chlorella/efeitos da radiação , Selênio/metabolismo , Aminoácidos/análise , Biomassa , Chlorella/classificação , Chlorella/crescimento & desenvolvimento , Processos Heterotróficos , Microalgas/química , Microalgas/crescimento & desenvolvimento , Microalgas/metabolismo , Microalgas/efeitos da radiação , Processos Fototróficos , Selênio/análise
2.
J Photochem Photobiol B ; 199: 111629, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31610433

RESUMO

The water-soluble semiconductor quantum dots (QDs) serve as optically detectable models of nanoparticles and are commonly applied as photoluminescent markers in biological systems. The unicellular algae represent a popular model system suitable to evaluate pollution-induced effects. There is growing experimental evidence that release of metal ions cannot account for potential toxicity of metal containing nanoparticles, however, the underlying mechanisms are not clearly understood. Surrounding environment and illumination conditions are among the most important factors affecting the stability of QDs as well as the interaction between nanoparticles and cells such as microalgae. The measurements of changes in photoluminescence (PL) of QDs and autofluorescence (AF) of microalgae can thus be used as a non-invasive screening method for detecting mutual effects of nanoparticles and algae cells on each other under natural conditions. In this study, CdTe quantum dots (a peak of PL at 550 nm) capped with a mercaptosuccinic acid (MSA) were introduced into aqueous ionic medium containing wild type green freshwater microalgae Scenedesmus and Chlorella sp. cells under artificial and natural ambient illumination. The spectroscopy and microscopy techniques were applied to observe both the influence of the microalgae on the spectral properties of negatively charged CdTe-MSA quantum dots and the effects of nanoparticles on the microalgae. The presence of algae cells revealed a protecting effect on both medium-dependent and radiation-induced changes in photoluminescence properties of QDs, which could be related with the increased stability of the capping layer. The effects on cellular AF intensity and the interaction of QDs with cellular surface depended on type of microalgae. The observed changes in AF spectral properties and AF induction signals can't be explained only by the photodegradation of QDs and have revealed the ability of nanoparticles to retard the photoadaptation of wild type microalgae under naturally varying illumination conditions.


Assuntos
Compostos de Cádmio/química , Corantes Fluorescentes/química , Microalgas/metabolismo , Pontos Quânticos/química , Telúrio/química , Tiomalatos/química , Chlorella/metabolismo , Água Doce , Luz , Scenedesmus/metabolismo , Espectrometria de Fluorescência , Propriedades de Superfície
3.
Ecotoxicol Environ Saf ; 185: 109691, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31563746

RESUMO

The rational use and the environmental safety of chiral pesticides have attracted significant research interest. Here, enantioselective toxic effects and the selective toxic mechanism of triticonazole (TRZ) against the aquatic microalgae Chlorella pyrenoidosa were studied. The 96h-EC50 values of rac-, (R)-(-)-, and (S)-(+)-TRZ were 1.939, 0.853, and 22.002 mg/L, respectively. At a concentration of 1 mg/L, the contents of photosynthetic pigments of C. pyrenoidosa exposed to (R)-(-)-TRZ were lower than if exposed to S-(+)-form and racemate. Transmission electron microscopic images showed that the R-(-)-form compromised the integrity of cells and disrupted the chloroplast structure. R-(-)-TRZ stimulated vast reactive oxygen species (ROS) and significantly increased superoxide dismutase (SOD) and catalase (CAT) activities, as well as malondialdehyde (MDA) content. For lipid accumulation experiments, nicotinamide adenine dinucleotide (NADH) and triacylglycerol (TAG) accumulations in algal cells treated with R-(-)-TRZ were 171.50% and 280.76%, respectively, compared with the control group. This far exceeded levels of algal cells treated with S-(+)- and rac-TRZ. Based on these data, R-(-)-TRZ was concluded to selectively affect the photosynthetic system, antioxidant system, and lipid synthesis of algal cells, thus causing enantioselective toxic effects of TRZ against C. pyrenoidosa, which indicating that the use of racemate may cause unpredictable environmental harm. Therefore, to reduce the hidden dangers of chiral pesticides for the ecological environment, the environmental risk of TRZ should be evaluated at the stereoselective level.


Assuntos
Chlorella/efeitos dos fármacos , Ciclopentanos/toxicidade , Fungicidas Industriais/toxicidade , Microalgas/efeitos dos fármacos , Triazóis/toxicidade , Poluentes Químicos da Água/toxicidade , Antioxidantes/metabolismo , Chlorella/metabolismo , Chlorella/ultraestrutura , Cloroplastos/efeitos dos fármacos , Cloroplastos/metabolismo , Ciclopentanos/química , Fungicidas Industriais/química , Malondialdeído/farmacologia , Microalgas/metabolismo , Microalgas/ultraestrutura , Fotossíntese/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Estereoisomerismo , Superóxido Dismutase/metabolismo , Triazóis/química , Poluentes Químicos da Água/química
4.
Environ Pollut ; 255(Pt 1): 113149, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31522007

RESUMO

Antibiotics have been widely detected in the ocean and have various impacts on the environment, while knowledge of their chronic influence on phytoplankton, especially red tide algae, is still limited. Dinoflagellates and green algae are common phytoplankton in marine ecosystems. The former is the main red tide algae, and the latter is an important primary producer. We investigated the long-term responses of two representative algae, Prorocentrum lima and Chlorella sp., to two common antibiotics (sulfamethoxazole (SMX) and norfloxacin (NFX)) at environmentally relevant levels (10 and 100 ng/L) during simulated natural conditions. The cell density and activities of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD)) were analyzed. The results showed that the influence of each antibiotic on Chlorella sp. was not significant (p > 0.05) during the first 10 days, but the influence of the antibiotics later began to show significant inhibition (p < 0.05) compared with the control group, especially during mixed exposure. P. lima was not inhibited, but its cell density increased. SMX had a superior stimulation effect on P. lima. The three enzymes activities of P. lima increased, and the antioxidant mechanism was not seriously impacted. However, for Chlorella sp., the activity of SOD increased while the activities of CAT and POD decreased, suggesting that this algae's antioxidant system was unbalanced due to oxidative stress. Based on our results, the growth of P. lima was different from green algae Chlorella sp. as well as other inhibited marine algae (such as diatom, golden algae) studied in previous studies. Therefore, as a typical pollutant in the ocean, antibiotics may play a positive role in the bloom of dinoflagellate red tides.


Assuntos
Antibacterianos/farmacologia , Chlorella/efeitos dos fármacos , Dinoflagelados/efeitos dos fármacos , Proliferação Nociva de Algas/efeitos dos fármacos , Norfloxacino/farmacologia , Sulfametoxazol/farmacologia , Poluentes da Água/farmacologia , Antioxidantes/metabolismo , Catalase/metabolismo , Chlorella/metabolismo , Dinoflagelados/metabolismo , Ecossistema , Peroxidase/metabolismo , Peroxidases/metabolismo , Superóxido Dismutase/metabolismo , Fatores de Tempo
5.
J Biosci ; 44(4)2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31502567

RESUMO

Constantly rising energy demands, finite fossil fuel reserves and deteriorating environmental conditions have invoked worldwide interest to explore the sustainable sources of renewable biofuels. Locally adapted photosynthetic oleaginous microalgae with rapid growth on variable temperatures could be an ideal way for bioremediating the wastewater (WW) while producing the feedstock for biodiesel. To test this notion, an unknown strain was isolated from a sewage fed lake (Neela-Hauz). It was discerned as Chlorella sorokiniana-I using the 16S rDNA and 18S rDNA barcodes. The culture conditions such as pH, illumination, different temperature ranges and growth medium were cohesively optimized prior to the assessment of C. sorokiniana-I's efficacy to remediate the WWand biodiesel production. The strain has thrived well up to 40°C when continuously grown for 15 days. The highest lipid accumulation and biomass productivity were recorded in 100% WW. Fatty acid methyl ester (FAME) content was observed to be more than twice in WW (47%), compared to control synthetic media, TAP (20%) and BG11 (10%), which indicate the importance of this new isolate for producing economically viable biodiesel. Moreover, it is highly efficient in removing the total nitrogen (77%), total phosphorous (81%), iron (67%) and calcium (42%) from the WW. The quality of WW was considerably improved by reducing the overall chemical oxygen demand (48%), biological oxygen demand (47%) and alkalinity (15%). Thus, C. sorokiniana-I could be an ideal alga for the tropical countries in the remediation of WW while producing feedstock for biodiesel in a cost-effective manner.


Assuntos
Biodegradação Ambiental , Chlorella/genética , Recuperação e Remediação Ambiental , Estágios do Ciclo de Vida/genética , Biocombustíveis , Biomassa , Chlorella/crescimento & desenvolvimento , Chlorella/metabolismo , Meios de Cultura , Ácidos Graxos/química , Ácidos Graxos/genética , Humanos , Lipídeos/química , Lipídeos/genética , Microalgas , Nitrogênio/metabolismo , Águas Residuárias/química
6.
Microb Pathog ; 135: 103658, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31398531

RESUMO

The increasing resistance of Pseudomonas aeruginosa towards antimicrobial agents has been a major cause for the escalation of untreatable diabetic foot ulcer cases around the globe. This demands research towards alternative natural products that inhibit biofilm formation by P. aeruginosa. The study focuses on enhancing as well as understanding the anti-biofilm property of lutein from Chlorella pyrenoidosa against MTCC strain of P. aeruginosa PAO1. C. pyrenoidosa was subjected to nutrient starvation (N-, S- and P-) and their growth, biomass, chlorophyll pigments and total carotenoids were estimated. Lutein extracted from nutrient starved C. pyrenoidosa were quantified using High Performance Liquid Chromatography (HPLC) and also used for quantification of biofilm formation, cell surface hydrophobicity (CSH), extracellular polymeric substances (EPS) and pyocyanin degradation. The results showed 20 µg/mL concentration of lutein showed maximum inhibition and degradation of biofilm formation, pyocyanin production, Cell Surface Hydrophobicity Extracellular Polymeric Substances, when compared to other concentrations. Azithromycin was used as a standard drug to compare the efficiency of lutein as a potential antibiofilm compound. Docking studies confirmed the interaction of lutein with the four proteins - LasI, LasR, RhlI and RhlR, involved in the quorum sensing mechanism during biofilm formation. Among them, RhlI protein was found to strongly interact and LasI exhibiting the least interaction with lutein. Gene expression analyses of las and rhl genes in P. aeruginosa PAO1 revealed a significant down regulation of both the genes in the cultures treated with different concentrations of lutein. Therefore, it can be understood that lutein is an effective antibiofilm agent and can be used in combination with generic drugs that are used for treating diseases such as diabetic foot ulcers, which are ineffective due to high biofilm forming capability of P. aeruginosa and other bacterial species.


Assuntos
Biofilmes/efeitos dos fármacos , Chlorella/metabolismo , Luteína/farmacologia , Pseudomonas aeruginosa/efeitos dos fármacos , Percepção de Quorum/efeitos dos fármacos , Azitromicina/farmacologia , Proteínas de Bactérias/genética , Biofilmes/crescimento & desenvolvimento , Biomassa , Carotenoides , Parede Celular/efeitos dos fármacos , Clorofila , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Interações Hidrofóbicas e Hidrofílicas/efeitos dos fármacos , Ligases/genética , Luteína/química , Microalgas , Simulação de Acoplamento Molecular , Pseudomonas aeruginosa/genética , Piocianina/metabolismo , Percepção de Quorum/genética , Transativadores/genética , Fatores de Transcrição/genética
7.
Bioresour Technol ; 291: 121783, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31326682

RESUMO

Microalgae are feedstocks for multiple product development based on algal biorefinery concept. The effects of light quality (white, red and blue light emitting diodes) and macro-element starvations on Chlorella sp. AE10 were investigated under 20% CO2 and 850 µmol m-2 d-1. Nitrogen and phosphorus starvations had negative effects on its growth rate. The biomass productivities were decreased from day 1 and the highest one was 1.90 g L-1 d-1 under white light conditions. Phosphorus starvation promoted carbohydrate accumulation under three LED light sources conditions and the highest carbohydrate content was 75.9% using red light. Blue light increased lutein content to 9.58 mg g-1. The content of saturated fatty acids was significantly increased from 37.51% under blue light and full culture medium conditions to 77.44% under blue light and nitrogen starvation conditions. Chlorella sp. AE10 was a good candidate for carbohydrate and lutein productions.


Assuntos
Carboidratos/biossíntese , Chlorella/metabolismo , Ácidos Graxos/biossíntese , Luteína/biossíntese , Biomassa , Chlorella/crescimento & desenvolvimento , Ácidos Graxos/análise , Luz , Nitrogênio/metabolismo , Fósforo/metabolismo
8.
Bioresour Technol ; 289: 121746, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31323709

RESUMO

This study focused on the effect of hydrothermal treatment (HTT) on biochemical methane potential (BMP) of Chlorella sp. The BMP was in the range of 119.16-485.90 mLCH4/gVS, and increased by 80.31%-210.16% after HTT, while reduced 23.94% at hydrothermal treatment severity (HTS) 5.21. The cell wall was more greatly disrupted with increasing HTS, accompanied with the increase of volatile fatty acids (VFAs) and fermentation inhibitors (5-HMF and more complex chemical compositions) recoveries. The reducing sugar yields were 0.94-3.65% and obtained its maximum at a retention time of 30 min. Illumina MiSeq sequencing clarified that, the phylum Chloroflexi with functions of hydrolysis and acidogenesis, decreased with increasing HTS. The family Methanosaetaceae belonging to acetoclastic methanogens, had an unexpected decrease at HTS 5.21. As the response, VFAs concentration was less than 1 g/L after biochemical metabolism, while high concentrations of VFAs and inhibitors at HTS 5.21 led to the poor performance.


Assuntos
Chlorella/metabolismo , Metano/metabolismo , Fenômenos Bioquímicos , Metabolismo dos Carboidratos , Carboidratos , Ácidos Graxos Voláteis/biossíntese , Hidrólise
9.
Bioresour Technol ; 289: 121741, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31323710

RESUMO

In this study, the effect of microalgal strains on the formation of algal-bacterial biofloc was investigated in liquid digestate pretreated by a sequencing batch reactor (SBR), which loaded much aerobic bacteria from activated sludge. Six microalgal strains resulted in three cases: no-bioflocculation (Scenedesmus obliquus and Botryococcus braunii), optimal-bioflocculation with high flocculation activity and good growth (Chlorella sp. BWY-1, Haematococcus pluvialis and Dictyosphaerium ehnenbergianum) and over-bioflocculation with high flocculation activity and bad growth (Chlorella vulgaris). Chlorella sp. BWY-1 provided a better level of flocculation activity and growth. Polysaccharides and proteins were present in EPS of algal-bacterial biofloc, and their distribution was confirmed by staining with alcian blue and fluorescein isothiocyanate (FITC).


Assuntos
Chlorella/metabolismo , Microalgas/metabolismo , Esgotos/microbiologia , Aquicultura , Floculação , Polissacarídeos/metabolismo
10.
Bioresour Technol ; 291: 121820, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31344639

RESUMO

Mixotrophy (M) assumes sum of autotrophic (A) and heterotrophic (H) growths. In this study, a novel split-mixotrophic cultivation strategy (SMCS) developed as better mixotrophy via offering mutual-benefits through gas-exchange at both headspaces while splitting both trophic modes. To quantify synergistic-growth effects in combined-autotrophy and combined-heterotrophy (CA&CH) of SMCS, gross O2-evolution, DIC and DO concentrations were compared with A, H and M. Average 12-14% and 26-32% increase in DIC and DO concentrations were determined respectively in CA and CH than A, H and M. Biomass yield in CA + CH was increased approx.1.5-folds higher than yields of A + H and M regimes. These results show SMCS as better cultivation strategy than the M by increased biomass and lipid yields. Challenges associated with organic carbon can be solved by SMCS viz. chlorophyll loss, organic carbon uptake inhibition. SMCS could be a breakthrough to integrate bacterial process with algae for better bioprocess economy and energy recovery.


Assuntos
Biomassa , Chlorella/metabolismo , Lipídeos/biossíntese , Processos Autotróficos , Chlorella/crescimento & desenvolvimento , Clorofila/metabolismo , Processos Heterotróficos
11.
Bioresour Technol ; 289: 121701, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31271917

RESUMO

The suitability of integrating biological and thermal transformation of microalgal biomass to design a biorefinery was studied. The mixed cultivation of Chlorella sp. and Bracteacoccus sp. in city wastewater produced 12 g L-1 of biomass (0.77 g L-1 day-1) and removed nitrates and phosphates by 68% and 75%, respectively. Microalgae outcompeted the contaminating microbes by raising the pH of wastewater to 9.93. The lipid-free residual biomass was pyrolyzed at four heating rates (10, 20, 30, 40 °C min-1) which showed a three-stage pyrolysis. The activation energies (182-256 kJ mol-1) and their corresponding lower enthalpies at the conversional fractions from 0.2 to 0.6 indicated that product formation was being favored. The values of pre-exponential factors (1015-17 s-1), Gibbs free energy (159-190 kJ mol-1) and entropy (43-81 J mol-1) showed efficient pyrolysis. The data may lead to establish a robust microalgal biorefinery to produce biomass and energy along with primary treatment of city wastewater.


Assuntos
Biomassa , Chlorella/metabolismo , Clorofíceas/metabolismo , Microalgas/metabolismo , Temperatura Alta , Cinética , Pirólise , Termodinâmica , Águas Residuárias
12.
Bioresour Technol ; 289: 121762, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31311731

RESUMO

In this work, glucose addition (0.7 g l-1) almost doubled hydrogen yield of Chlorella pyrenoidosa (121.1 ml l-1 vs 65.5 ml l-1), with a positive correlation between hydrogen production and glucose consumption (-0.977, P < 0.01). When the electrons transport from water photolysis to algal hydrogenase was inhibited, the hydrogen productivity declined by 21.1%; whereas it dramatically decreased by 70.9% when the algal nicotinamide adeninedinucleotide dehydrogenase (NADH) was inhibited. Therefore, in the presence of glucose, the electrons for algae based hydrogen production would be mainly from glucose glycolysis rather than water photolysis. Further deuterated-glucose trial indicated that the glucose might serve as an electron donor for algal hydrogenases. Finally, a tentative electron transport route from glucose to algal hydrogenase was proposed, hoping to provide more scientific direction for further algae-based hydrogen production improvement.


Assuntos
Chlorella/metabolismo , Hidrogênio/metabolismo , Hidrogenase/metabolismo , Transporte de Elétrons , Elétrons , Glucose/metabolismo , Fotólise
13.
Microb Cell Fact ; 18(1): 113, 2019 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-31253148

RESUMO

BACKGROUND: Microalgae have been proposed as potential platform to produce lipid-derived products, such as biofuels. Knowledge on the intracellular carbon flow distribution may identify key metabolic processes during lipid synthesis thus refining culture/genetic strategies to maximize cell lipid productivity. A kinetic metabolic model simulating cell metabolic behavior and lipid production was first applied in the microalgae platform Chlorella protothecoides under heterotrophic condition. It combines both physiology and flux information in a kinetic approach. Cell nutrition, growth, lipid production and almost 30 metabolic intermediates covering central carbon metabolism were included and simulated. RESULTS: Model simulations were shown to adequately agree with experimental data, which is suggesting that the proposed model copes with Chlorella protothecoides cells' biology. The dynamic metabolic flux analysis using the model showed a reversible starch flux from accumulation to decomposing when glucose reached depletion, while net lipid flux shows a quasi-constant rate. The sensitive flux parameters on starch and lipid metabolism suggested that starch synthesis is the major competing pathway that affects lipid accumulation in C. protothecoides. Flux analysis also demonstrated that high lipid yield under heterotrophic condition is accompanied with high lipid flux and low TCA activity. Meanwhile, the dynamic flux distribution also suggests a relatively constant ratio of glucose distributed to biomass, lipid, starch, nucleotides as well as pentose phosphate pathway. CONCLUSION: The model described not only experimental data, but also unraveled intracellular carbon flow distribution and identify key metabolic processes during lipid synthesis. Most of the metabolic kinetics also showed statistical significance for metabolic mechanism. Therefore, this study unravels the mechanisms of the glucose impact on the dynamic carbon flux distribution, thus improving our understanding of the links between carbon fluxes and lipid metabolism in C. protothecoides.


Assuntos
Chlorella/metabolismo , Lipídeos/biossíntese , Lipídeos/química , Carbono/metabolismo , Chlorella/química , Chlorella/crescimento & desenvolvimento , Glucose/metabolismo , Processos Heterotróficos , Cinética , Análise do Fluxo Metabólico , Microalgas/química , Microalgas/crescimento & desenvolvimento , Microalgas/metabolismo , Via de Pentose Fosfato , Amido/metabolismo
14.
Bioresour Technol ; 289: 121686, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31238290

RESUMO

Chlorella kessleri accumulates triacylglycerol usable for biodiesel-fuel production to >20% dry cell weight in three days when cultured in three-fold diluted seawater, which imposes the combinatory stress of hyperosmosis and nutrients limitation. The quantitative behavior of major C-compounds, and related-gene expression patterns were investigated in Chlorella cells stressed with hyperosmosis, nutrients limitation, or their combination, to elucidate the C-metabolism for economical seawater-based triacylglycerol accumulation. Combinatory-stress cells showed repressed protein synthesis with initially accumulated starch being degraded later, the C-metabolic flow thereby being diverted to fatty acid and subsequent triacylglycerol accumulation. This C-flow diversion was induced by cooperative actions of nutrients-limitation and hyperosmosis. Semi-quantitative PCR analysis implied positive rewiring of the diverted C-flow into triacylglycerol in combinatory-stress cells through upregulation of gene expression concerning fatty acid and triacylglycerol synthesis, and starch synthesis and degradation. The information of regulatory C-metabolism will help reinforce the seawater-based triacylglycerol accumulation ability in algae including Chlorella.


Assuntos
Carbono/metabolismo , Chlorella/metabolismo , Triglicerídeos/biossíntese , Biocombustíveis , Ácidos Graxos/metabolismo , Água do Mar , Amido/metabolismo
15.
Chemosphere ; 233: 363-372, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31176899

RESUMO

Titanium dioxide nanoparticles (TiO2 NPs) find applications in our day-to-day life because of unique physicochemical properties. Their release into the aquatic environment poses a possible risk to the organisms. However, the continuing exposure of NPs might reduce their bioavailability to marine organisms owing to aggregation and sedimentation in the aqueous systems thus significantly reducing their toxic impact. In this regard, the present study investigates the effect of continuous exposure of TiO2 NPs to marine microalgae Chlorella sp. under UV-A irradiation through "tanks in series" mode of experiments. In a three-cycle experiment, concentration of TiO2 NPs in the first cycle was fixed at 62.6 µM, and the interacted nanoparticles was subsequently exposed to fresh batches of algae in the next two cycles. After the interaction, the NPs underwent severe aggregation (mean hydrodynamic diameter 3000 ±â€¯18.2 nm after cycle I) leading to gravitational settling in the medium and thus decreased bioavailability. The aggregation can be attributed to interactions between the particles themselves (homo-aggregation) further aggravated by the presence of the algal cells (hetero-aggregation). Cellular viability after cycle I was found to be only 24.2 ±â€¯2.5%, and it was enhanced to 96.5 ±â€¯2.8% after the cycle III in the course of continuous exposure. The results were validated with estimation of oxidative stress markers such as intracellular ROS (total ROS, superoxide and hydroxyl radicals) and LPO after each cycle of exposure. The continuing decrease in the EPS across the cycles further confirmed the diminishing toxicity of the NPs.


Assuntos
Organismos Aquáticos/efeitos dos fármacos , Chlorella/efeitos dos fármacos , Microalgas/efeitos dos fármacos , Nanopartículas/toxicidade , Titânio/toxicidade , Poluentes Químicos da Água/toxicidade , Organismos Aquáticos/metabolismo , Disponibilidade Biológica , Chlorella/metabolismo , Exposição Ambiental , Microalgas/metabolismo , Modelos Teóricos , Nanopartículas/química , Estresse Oxidativo/efeitos dos fármacos , Tamanho da Partícula , Titânio/química , Titânio/metabolismo , Raios Ultravioleta , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo
16.
Chemosphere ; 234: 796-805, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31247489

RESUMO

Naphthenic acids (NAs) originate from bitumen and are considered a major contributor to acute toxicity in oil sands process-affected water (OSPW) produced from bitumen extraction processes. To reclaim oil sands tailings and remediate OSPW, in-pit fluid fine tailings can be water-capped as end pit lakes (EPL). Addressing NAs present in OSPW, either through removal, dilution or degradation, is an objective for oil sands reclamation. EPLs can remediate NAs through degradation or dilution or both. To assess and understand degradation potential, Chlorella kessleri and Botryococcus braunii were tested for their tolerance to, and ability to biodegrade, three model NAs (cyclohexanecarboxylic acid, cyclohexaneacetic acid, and cyclohexanebutyric acid). Water sourced from the industry's first EPL, the Base Mine Lake (BML), was used alone as an inoculum or co-cultured with C. kessleri to biodegrade cyclohexanecarboxylic acid and cyclohexanebutyric acid. All cultures metabolized the model compounds via ß-oxidation. Biodegradation by the co-culture of C. kessleri and BML inoculum was most effective and rapid: the cyclohexaneacetic acid generated from cyclohexanebutyric acid could be further degraded by the co-culture, while the cyclohexaneacetic acid generated could not be consumed by pure algal cultures or BML inoculum alone. Adding C. kessleri greatly increased the diversity of the microbial community in the BML inoculum; many known hydrocarbon and NA degraders were identified from the 16S rRNA gene sequencing from this co-culture. This more diverse microbial community could have potential for EPL remediation.


Assuntos
Biodegradação Ambiental , Ácidos Carboxílicos/metabolismo , Lagos/microbiologia , Microalgas/metabolismo , Campos de Petróleo e Gás/microbiologia , Acetatos/metabolismo , Inoculantes Agrícolas/metabolismo , Butiratos/metabolismo , Chlorella/metabolismo , Cicloexanos/metabolismo
17.
J Agric Food Chem ; 67(19): 5579-5586, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-31038310

RESUMO

The growth and astaxanthin production of Chlorella zofingiensis were examined under both heterotrophic and photoautotrophic conditions, and it was found that, in comparison to the photoautotrophic mode, the heterotrophic mode led to high algal densities but attenuated intracellular astaxanthin accumulation. Following the heterotrophy-photoautotrophy transition, a considerable increase in the astaxanthin content was observed, accompanied by the upregulation of key carotenogenic genes, including phytoene synthase (PSY), ß-carotenoid hydroxylase (CHYb), ß-carotenoid ketolase 1 (BKT1), and ß-carotenoid ketolase 2 (BKT2). In contrast, the astaxanthin content and carotenogenic genes underwent an opposite change following the photoautotrophy-heterotrophy transition, suggesting the key role of light in stimulating astaxanthin biosynthesis. To improve the astaxanthin production by C. zofingiensis, a novel heterotrophy-photoinduction culture strategy without dilution was developed and evaluated. The astaxanthin content and productivity reached 2.7 mg g-1 of dry weight and 9.9 mg L-1 day-1, respectively, which were 4.0- and 2.5-fold higher than that obtained under the heterotrophic condition.


Assuntos
Chlorella/metabolismo , Chlorella/efeitos da radiação , Carotenoides/metabolismo , Chlorella/enzimologia , Chlorella/genética , Fermentação , Geranil-Geranildifosfato Geranil-Geraniltransferase/genética , Geranil-Geranildifosfato Geranil-Geraniltransferase/metabolismo , Luz , Xantofilas/biossíntese
18.
Bioresour Technol ; 287: 121414, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31078813

RESUMO

An increase in the total lipid content in algal cells under stress conditions is often accompanied by an increase in reactive oxygen species (ROS). However, the link between these two events is unclear. In this study, the regulatory mechanism of ROS formation on lipid accumulation in C. pyrenoidosa was investigated using a Fenton-like reaction. A high Spearman correlation coefficient of 0.901 was obtained between the Hydroxyl radical (OH) level and lipid content. Importantly, the increase in the total lipid content was clearly coupled with a significant increase in the intracellular OH concentration rather than increases in the H2O2 and O2- concentrations. Transcriptome data confirms that most of the differential expression genes (DEGs) involved in fatty acid and glycerolipid biosynthesis were up-regulated by the increased OH under stress conditions. These results reveal that lipid accumulation in algal cells was promoted by OH.


Assuntos
Chlorella/metabolismo , Lipídeos/biossíntese , Espécies Reativas de Oxigênio/metabolismo , Peróxido de Hidrogênio/metabolismo , Radical Hidroxila/metabolismo , Espaço Intracelular/metabolismo
19.
Environ Pollut ; 250: 914-921, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31085478

RESUMO

China has been faced with severe haze pollution, which is hazardous to human health. Among the air pollutants, PM2.5 (particles with an aerodynamic diameter ≤ 2.5 µm) is the most dangerous because of its toxicity and impact on human health and ecosystems. However, there has been limited research on PM2.5 particle toxicity. In the present study, we collected daily PM2.5 samples from January 1 to March 31, 2018 and selected samples to extract water-soluble species, including SO42-, NO3-, WSOC, and NH4+. These samples represented clean, good, slight, moderate, and heavy pollution days. After extraction using an ultrasonic method, PM2.5 solutions were obtained. We used Chlorella as the test algae and studied the content of chlorophyll a, as well as the variation in fluorescence when they were placed into the PM2.5 extraction solution, and their submicroscopic structure was analyzed using transmission electron microscopy (TEM). The results showed that when the air quality was relatively clean and good (PM2.5 concentration ≤ 75 µg m-3), the PM2.5 extraction solutions had no inhibiting effects on Chlorella, whereas when the air quality was polluted (PM2.5 concentration > 75 µg m-3) and heavily polluted (PM2.5 concentration > 150 µg m-3), with increasing PM2.5 concentrations and exposure time, the chlorophyll a content in Chlorella decreased. Moreover, the maximum photochemical quantum yield (Fv/Fm) of Chlorella obviously decreased, indicating chlorophyll inhibition during polluted days with increasing PM2.5 concentrations. The effects on the chlorophyll fluorescence parameters were also obvious, leading to an increase of energy dissipated per unit reaction center (DIo/RC), suggesting that Chlorella could survive when exposed to PM2.5 solutions, whereas the physiological activities were significantly inhibited. The TEM analysis showed that there were few effects on Chlorella cell microstructure during clean days, whereas plasmolysis occurred during light- and medium-polluted days. With increasing pollution levels, plasmolysis became more and more apparent, until the organelles inside the cells were thoroughly destroyed and most of the parts could not be recognized.


Assuntos
Poluentes Atmosféricos/toxicidade , Poluição do Ar/análise , Chlorella/efeitos dos fármacos , Monitoramento Ambiental/métodos , Material Particulado/toxicidade , Poluentes Atmosféricos/análise , China , Chlorella/metabolismo , Clorofila A/metabolismo , Humanos , Tamanho da Partícula , Material Particulado/análise , Solubilidade , Testes de Toxicidade , Água/química
20.
Environ Sci Pollut Res Int ; 26(20): 20815-20828, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31111387

RESUMO

The effects of iron (Fe), zinc (Zn), and molybdenum (Mo) on the biomass yield, lipid content, lipid yield, and fatty acid composition of Chlorella sp. NC-MKM, Graesiella emersonii NC-M1, Scenedesmus acutus NC-M2, and Chlorophyta sp. NC-M5 were studied. Among them, G. emersonii NC-M1 recorded the highest percentage increase in lipid content (140.3%) and neutral lipid (50.9%) under Zn-supplemented condition compared to the control. Also, it showed a 105% and 41.88% increase in lipid yield and neutral lipid under Fe-supplemented condition compared to the control. However, Chlorella sp. NC-MKM recorded an elevation in lipid yield (70.3% rise) and neutral lipid (24.32% rise) compared to the control in Mo-supplemented condition. The enhanced production of reactive oxygen species (ROS) and antioxidant enzyme (SOD and POD) under Fe-, Zn-, and Mo-supplemented condition supports the lipid accumulation. FAME analysis showed that the overall percentage of SFA and MUFA increased after the addition of Fe, Zn, and Mo in a culture medium compared to the control which is vital for a good-quality biodiesel. Further, biodiesel properties derived from FAMEs such as CN, SV, IV, CFPP, OS, υ, ρ, and HHV were found in accordance with biodiesel standard.


Assuntos
Ferro/farmacologia , Metabolismo dos Lipídeos/efeitos dos fármacos , Microalgas/efeitos dos fármacos , Molibdênio/farmacologia , Zinco/farmacologia , Biocombustíveis , Chlorella/efeitos dos fármacos , Chlorella/metabolismo , Clorófitas/efeitos dos fármacos , Clorófitas/metabolismo , Meios de Cultura/química , Meios de Cultura/farmacologia , Ácidos Graxos/análise , Lipídeos/química , Microalgas/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Scenedesmus/efeitos dos fármacos , Scenedesmus/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA