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1.
Bioresour Technol ; 301: 122743, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31945684

RESUMO

The aim of this work was to investigate the potential of PEF technology for green extraction of microalgal pigments and lipids from fresh Chlorella sorokiniana suspensions. Efficiencies of PEF treatment and different solvent systems application to C.sorokiniana were compared to efficiencies of untreated biomass extraction. Differences in chlorophyll extraction of untreated and PEF treated C.sorokiniana were only seen at short extraction times. Beneficial PEF-effect was minimised for long-time extractions of larger algae quantities where yields aligned. Extraction attempts on C. sorokiniana lipids did not show increased extractability after PEF treatment, which underlined the statement of PEF representing a rather ineffective disruption method for microalgae holding rigid cell walls.


Assuntos
Chlorella , Microalgas , Biomassa , Clorofila , Eletricidade
2.
Water Res ; 171: 115445, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31954203

RESUMO

Ammonium removal by a coupling process of microalgae (Chlorella sorokiniana) with partial nitrifying granules was evaluated in batch reactors illuminated in a wide range of light intensities (0, 100, 450, and 1600 µmol photons m-2 s-1). Ammonium oxidation performance for different light exposure time showed that the granules had a light stress tolerance at 1600 µmol photons m-2 s-1 for up to 12 h, but continuous illumination induced severe inhibition on nitrifying bacteria thereafter. Ammonium removal efficiencies at the end of tests were 66%, 62%, 5%, and -10% (due to ammonification) for 0, 100, 450, and 1600 µmol photons m-2 s-1, respectively. The nitrogen mass balance shows co-occurrence of microalgal growth taking up 24% of fed ammonium and nitrifying bacteria oxidizing 38% of fed ammonium at 100 µmol photons m-2 s-1, while both nitrification and microalgal growth are inhibited at light intensity above 450 µmol photons m-2 s-1. In comparing results from this study with previous results, it was found that the ammonium removal pathway, i.e., nitrification or microalgal uptake, is regulated more strongly by daily average light intensity than by instantaneous light intensity. Empirical model equations to estimate the oxygen balance in consortium reactors categorized the effect of daily average light intensities on process performance as follows: (i) below 27 µmol photons m-2 s-1: insufficient oxygen for nitrification; (ii) 27 to 35: sufficient oxygen for nitrification via nitrite; (iii) 35 to 180: sufficient oxygen for nitrification via nitrate; (iv) above approximately 200-300: oversaturated dissolved oxygen, excess free ammonia and/or intensive light inhibitions.


Assuntos
Compostos de Amônio , Chlorella , Microalgas , Amônia , Reatores Biológicos , Nitrificação , Nitritos , Nitrogênio
3.
Bioresour Technol ; 301: 122762, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31972402

RESUMO

To assess the potential of Chlorella sp. GN1 for producing biodiesel raw materials in flat plate photobioreactors (FPPs) outdoors, we optimized the nitrogen sources and concentrations for the growth of the algae. The effects of different light paths of FPPs on the growth, lipid accumulation, and fatty acids of Chlorella sp. GN1 were also studied. As the light path of the FPPs was reduced, the alga could accumulate lipids rapidly, achieving high lipid content and lipid productivity outdoors. The highest lipid content obtained was 53.5%, when the light path was 5 cm. In addition, the lipid productivity was 66.7 mg L-1 day-1. The main fatty acids were C16/C18, accounting more than 90% of the total fatty acids. Results showed that Chlorella sp. GN1 had the ability to accumulate large quantities of lipids in FPPs outdoors and was a promising microalgal species for biofuel production.


Assuntos
Chlorella , Microalgas , Biocombustíveis , Biomassa , Ácidos Graxos , Luz , Lipídeos , Nitrogênio , Fotobiorreatores
4.
Environ Technol ; 41(4): 400-410, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29995593

RESUMO

Current algal-bacterial consortia require high hydraulic retention times (HRTs, 2-10 days) to efficiently remove pollutants from domestic wastewaters. A novel algal-bacterial biofilm reactor was developed for a much lower HRT. The results showed that an HRT of 12 h ensured 90% removal of organic matter and ammonium, and phosphate removal was approximately 30%. Decreasing the HRT to 8 h significantly deteriorated the reactor's pollutant removal efficiencies and increasing the HRT to 24 h did not improve these efficiencies. Illumination, which was light source for algae, was provided by a LED light. Activity tests showed that organic matter and ammonium removal rates resulting from illumination were 70% and 50%, respectively, of the rates when dissolved oxygen concentration was maintained at 2 mg/L. Chemical oxygen demand (COD) removal rates resulted from illumination and aeration were 18.63 and 25.38 mg COD/L.h, respectively. The phosphate removal rate was 0.26 and 0.43 mg/L.h when illumination and aeration were applied, respectively. The ammonium removal rates were approximately 10,390 and 5000 mg [Formula: see text] when the reactor was aerated or illuminated, respectively. These two rates were significantly higher than reported nitrification rates. Moreover, the percentage of Oscillatoria sp. increased from below 10% to over 90% under the applied organic load and temperature, while the percentage of fast growing algae, Chlorella, chroococcus sp and Scenedesmus sp., decreased from over 90% to below 10%. These results showed that an algal-bacterial biofilm reactor with a low reactor footprint was developed.


Assuntos
Chlorella , Águas Residuárias , Biofilmes , Reatores Biológicos , Estudos de Viabilidade , Nitrogênio , Eliminação de Resíduos Líquidos
5.
Bioresour Technol ; 297: 122445, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31780245

RESUMO

The objective of this work was to test the impact of anaerobic digester microorganisms on algal growth, composition, and nutrient removal from digestate. Culture studies were carried out to determine the impacts of the microbial community on treatment of poultry litter anaerobic digestate by two strains of green algae: Auxenochlorella protothecoides and Chlorella sorokiniana. The results showed that the community doubled the growth of A. protothecoides but had no impact on C. sorokiniana growth. A similar result was observed for nutrient removal where the microbial community increased the capacity of A. protothecoides to remove ammonium and phosphate. The impact of the microbial community on biomass composition was minimal for both algae types.


Assuntos
Chlorella , Microbiota , Anaerobiose , Biomassa , Nutrientes
6.
J Sci Food Agric ; 100(3): 1072-1079, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31650550

RESUMO

BACKGROUND: Acid-induced hydrolysis of proteins has been used to improve the solubility and functional properties of various proteins, and could be a promising tool to facilitate the use of currently underutilized insoluble microalgae protein-rich fractions in food applications. However, the results of a prior study showed an unusual resistance of an insoluble microalgae protein-rich fraction to acid hydrolysis at room temperature. RESULTS: In the present study, the insoluble protein-rich fraction extracted from microalgae Chlorella prothothecoides was treated with 0.5 mol L-1 hydrochloric acid at 25, 45, 65 or 85 °C for 0-4 h. The results showed that hydrolysis of the fraction at 85 °C for 4 h led to decreases in the amount of insoluble protein-rich aggregates and the formation of fragments with a lower molecular weight, as well as an increase in protein solubility by approximately 40%. Nevertheless, some aggregated insoluble protein-rich particles remained, even after hydrolysis at 85 °C for 4 h. CONCLUSION: The higher temperature improved the efficiency of the acid hydrolysis of the insoluble protein fraction from microalgae Chlorella prothothecoides, which is highly acid-resistant. Overall, an erosion-based mechanism was suggested for the acid hydrolysis of insoluble microalgae protein fraction. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.


Assuntos
Chlorella/química , Proteínas/química , Fracionamento Químico , Temperatura Alta , Ácido Clorídrico/química , Hidrólise , Microalgas/química , Peso Molecular , Proteínas/isolamento & purificação , Solubilidade
7.
Waste Manag ; 102: 198-203, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31678806

RESUMO

An estimation of the economy of Hermetia illucens and Chlorella pyrenoidosa cultivations as food waste treatment with benefits was carried out. For both organisms, a process scale was assumed to treat 56.3 t of wet food waste per day, which is equivalent to the amount of food waste appearing in a catchment area of 141,000 inhabitants. Using hypothetical insect and heterotrophic microalgae cultivation processes, a daily production of 3.64 t and 7.14 t dried biomass, respectively, can be achieved. For the cultivation of H. illucens, equipment and daily operational costs were estimated at 79,358.15 € and 5,281.56 €, respectively. Equipment and operational costs for the C. pyrenoidosa cultivation was 50 and 6 times higher, respectively. The higher costs reflect the more complex and advanced process compared to H. illucens cultivation. The internal return rate for a plant lifetime of 20 times revealed an economic benefit when C. pyrenoidosa biomass is produced. Nevertheless, both processes were found economically feasible when dried biomass is directly commercialized as food without any further downstream processing. However, extraction and purification of special chemicals, such as unsaturated fatty acids and pigments, can significantly increase the revenue.


Assuntos
Chlorella , Microalgas , Eliminação de Resíduos , Animais , Biomassa , Alimentos , Processos Heterotróficos , Insetos , Águas Residuárias
8.
Bioresour Technol ; 297: 122379, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31735698

RESUMO

Insufficient organics in anaerobic digestate of sludge limited algal mixotrophic culture and caused low lipids production. In this study, enhancing lipids production and pollutants removal by adding acidified starch wastewater was tested for Chlorella pyrenoidosa mixotrophic culture. The results showed that an optimal addition of acidified starch wastewater into anaerobic digestate of sludge (1:1, v/v) improved biomass and lipids production by 0.5-fold (to 2.59 g·L-1) and 3.2-fold (87.3 mg·L-1·d-1), respectively. The acidified starch wastewater addition also improved the quality of algal biodiesel with higher saturation (typically in C16:0 and C18:0). In addition, 62% of total organic carbon, 99% of ammonium and 95% of orthophosphate in mixed wastewater were effectively removed by microalgae. This study provides a promising way to improve biodiesel production and nutrients recovery from anaerobic digestate of sludge using waste carbon source.


Assuntos
Chlorella , Microalgas , Anaerobiose , Biomassa , Carbono , Lipídeos , Nutrientes , Esgotos , Águas Residuárias
9.
J Sci Food Agric ; 100(3): 1344-1349, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31605384

RESUMO

BACKGROUND: Water-soluble proteins extracted from the heterotrophically cultivated microalga Chlorella protothecoides have been shown to have a good solubility over a broad pH range, which makes them a promising candidate for beverage formulations. This study investigated the sensory properties of dispersions of a protein-rich extract from C. protothecoides at neutral and pH 3. RESULTS: Sensory acceptance tests of the pure extract revealed an overall low acceptance at pH 7 without sucrose addition. Sensory acceptance was significantly (P ≤ 0.05) increased by lowering the pH to 3 with citric acid, and the addition of 50 g kg-1 sucrose. Here, overall positive sensory acceptance ratings were achieved up to a protein extract concentration of 40 g kg-1 . Basic taste evaluations showed only low bitterness scores and no significant (P > 0.05) increase in bitterness with decreasing pH. CONCLUSION: It is suggested that protein-rich extracts from C. protothecoides have promising sensory properties in beverage formulations. © 2019 The Authors. Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.


Assuntos
Chlorella/química , Extratos Vegetais/química , Proteínas de Plantas/química , Bebidas/análise , Chlorella/crescimento & desenvolvimento , Processos Heterotróficos , Humanos , Concentração de Íons de Hidrogênio , Microalgas/química , Microalgas/crescimento & desenvolvimento , Extratos Vegetais/isolamento & purificação , Proteínas de Plantas/isolamento & purificação , Solubilidade , Paladar
10.
Bioresour Technol ; 298: 122502, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31830659

RESUMO

Aqueous phase (AP) is the wastewater (byproduct) produced during hydrothermal treatment of biomass. This study aims to investigate the effect of AP recirculation on hydrochar from different types of biomass. Therefore, Chlorella (CL) and soybean straw (SS) were hydrothermally carbonized (HTC) at 220 °C for 240 min with AP recirculation for four cycles, respectively. The yield of hydrochar was increased from 20.5% to 26.7% for CL and from 47.7% to 54.7% for SS. More carbon distribution in hydrochar was observed, which increased the energy recovery from biomass by HTC by 10%-12%. Most fuel properties such as elemental compositions of the hydrochar were only slightly influenced by the AP recirculation. Furthermore, AP was used for algal cultivation, and the maximum biomass density of ~1.2 (inoculum optical density 680 nm of ~ 0.2) was obtained in CL AP without recirculation and in SS AP with three times of recirculation, respectively.


Assuntos
Chlorella , Microalgas , Biomassa , Carbono , Soja , Temperatura Ambiente
11.
Bioresour Technol ; 298: 122521, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31830660

RESUMO

Anaerobic co-digestion of primary sludge and raw microalgae (Scenedesmus and Chlorella) was performed in a lab-scale semi-continuous anaerobic membrane bioreactor to assess the biological performance and identify the microbial community involved in the co-digestion process. The reactor was operated at 35 °C for 440 days, working at a solids retention time of 100 days. The system achieved 73% biodegradability and showed high stability in terms of pH and volatile fatty acids. An enriched microbial community was observed. Of the several phyla, Chloroflexi and Proteobacteria were the most abundant. Cellulose-degraders phyla (Bacteroidetes, Chloroflexi and Thermotogae) were detected. Syntrophic microorganisms played an important role in intermediate degradation, enhancing methane production, mainly carried out by Methanosaeta. A nutrient-rich effluent (400 mg NH4-N·L-1 and 29 mg PO4-P·L-1) and digestate (860 mg N·L-1 and 151 mg P·L-1) were obtained. The bio-nutrients released from anaerobic co-digestion could be reused for microalgae cultivation or agricultural applications.


Assuntos
Chlorella , Microalgas , Anaerobiose , Reatores Biológicos , Metano , Esgotos
12.
Bioresour Technol ; 297: 122516, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31830716

RESUMO

Cultivating microalgae on wastewaters is an effective way to produce algal biomass whereas harvesting microalgae is a costly operation. This study we examined the feasibility of co-culturing a high-value microalga with an auto-flocculating strain to enable efficient recovery of biomass. Experiments were conducted to co-cultivate Chlorella zofingiensis with Tribonema sp. on swine wastewater diluted by fishery wastewater under different conditions. The result showed the optimal inoculum ratio of Tribonema sp. to Chlorella zofingiensis was 1:1. The removal efficiencies of pollutants (NH4+-N, TN, TP, and COD) and lipid content were high when the co-culture ratios of Tribonema sp. were high. Also, some larger chain fatty acids, specifically C20:5 and C22:6 were present when the two strains co-culture. The recovery efficiency increased with the increasing proportion of auto-flocculating Tribonema sp.. Algae co-culture has the potential to address limitations in substrate utilization by individual strains, also improve the recovery of biomass.


Assuntos
Chlorella , Microalgas , Animais , Biomassa , Técnicas de Cocultura , Pesqueiros , Nitrogênio , Suínos , Águas Residuárias
13.
Bioresour Technol ; 297: 122517, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31830719

RESUMO

Effects of different mixing ratios between synthetic municipal wastewater (MW) and magnesium (Mg2+)-enriched nickel laterite ore wastewater (NLOWW) on growth of Chlorella sorokiniana (C. sorokiniana), photosynthetic activities, cellular biocomposition, nutrient and Mg2+ removal were investigated in photobioreactors. In the culture without NLOWW, wrinkled cells were observed with low biomass production. The culture mixed with 0.13% NLOWW obtained 1.89-fold higher biomass yield, 3.77-fold enhanced photosynthetic activity (Fv/Fm value), and improved nutrient removal (nitrogen by 102.2%, phosphorus by 39.3%). However, excessive Mg2+ at 100% NLOWW produced highest reactive oxygen species suppressing microalgal growth. The Mg2+ removal capacity increased with NLOWW loading. Moreover, microalgal assimilation primarily contributed to nutrient removal while absorption was the dominant Mg2+ removal pathway. Carbohydrate content in biomass increased with Mg2+ loading. Finally, the approach for MW/NLOWW treatment was demonstrated as economically feasible with revenue of $75.6 per kilogram biomass through a comprehensive economic model.


Assuntos
Chlorella , Microalgas , Biodegradação Ambiental , Biomassa , Níquel , Nitrogênio , Nutrientes , Fósforo , Águas Residuárias
14.
Bioresour Technol ; 297: 122489, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31818721

RESUMO

A low-cost small-scale high-rate algal pond (HRAP) was constructed to investigate the synergistic potential of a novel oleaginous microalga, Chlorella sorokiniana for phyco-mitigation, and biodiesel production using raw urban wastewater. An enhanced nutrient removal (97%), total organic carbon (74%), alkalinity (70%) and hardness (75%) from the wastewater was obtained. The microalga dominated in the HRAP as ~90% increase in the dissolved oxygen with high biomass (1.13 g/L) was noted. The microalga biomass showed sufficient lipid content (~31% of dry cell weight) as compared to control (Bold's Basal media). The total lipid profiling of the microalga cultivated in wastewater showed augmentation in the levels of both storage and neutral lipids with good quality fatty acids composition. Moreover, the sucker fishes grew healthy in the treated wastewater with an increase in body weight.


Assuntos
Chlorella , Microalgas , Aquicultura , Biocombustíveis , Biomassa , Águas Residuárias
15.
J Agric Food Chem ; 68(5): 1186-1197, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31855431

RESUMO

A bioactive polysaccharide from microalga Chlorella pyrenoidosa (CPP) was successively prepared via DEAE-52 and G-100 columns. Nuclear magnetic resonance analysis showed that the main glycosidic bonds were composed of 1,2-linked-α-l-Fucp, 1,4-linked-α-l-Rhap, 1,4-linked-ß-l-Araf, 1-linked-α-d-Glcp, 1,3-linked-ß-d-GlcpA, 1,4-linked-ß-d-Xylp, and 1,3,6-linked-ß-d-Manp. Its molecular weight was 5.63 × 106 Da. The hypolipidemic effect and intestinal flora regulation of CPP on diet-induced rats were evaluated through histopathology and biochemistry analyses. CPP could improve plasma and liver lipid metabolism and accelerate the metabolism of the cecal total bile acids and short-chain fatty acids. CPP has also upregulated the adenosine-monophosphate-activated protein kinase α and downregulated the acetyl-CoA carboxylase, sterol regulatory element-binding protein 1c, and ß-hydroxy ß-methylglutaryl-CoA expressions. Moreover, with the 16S rRNA gene sequencing, it was revealed that the composition of intestinal flora changed drastically after treatment, such as the bloom of Coprococcus_1, Lactobacillus, and Turicibacter, whereas there was a strong reduction of the [Ruminococcus]_gauvreauii_group. The above results illustrated that CPP might be served as an effective ingredient to ameliorate lipid metabolism disorders and intestinal flora in hyperlipidemia rats.


Assuntos
Chlorella/química , Microbioma Gastrointestinal/efeitos dos fármacos , Hiperlipidemias/tratamento farmacológico , Microalgas/química , Extratos Vegetais/administração & dosagem , Polissacarídeos/administração & dosagem , Animais , Bactérias/classificação , Bactérias/efeitos dos fármacos , Bactérias/genética , Bactérias/isolamento & purificação , Humanos , Hiperlipidemias/metabolismo , Hiperlipidemias/microbiologia , Metabolismo dos Lipídeos/efeitos dos fármacos , Masculino , Extratos Vegetais/química , Polissacarídeos/química , Ratos , Ratos Wistar
16.
Sci Total Environ ; 699: 134365, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31677459

RESUMO

Methane production from microalgae can be enhanced through anaerobic co-digestion with carbon-rich substrates and thus mitigate the inhibition risk associated with its low C:N ratio. Acclimated microbial communities for microalgae disruption can be used as a source of natural enzymes in bioenergy production. However, co-substrates with a certain microbial diversity such as primary sludge might shift the microbial structure. Substrates were generated in a Water Resource Recovery Facility (WRRF) and combined as follows: Scenedesmus or Chlorella digestion and microalgae co-digestion with primary sludge. The study was performed using two lab-scale Anaerobic Membrane Bioreactors (AnMBR). During three years, different feedstocks scenarios for methane production were evaluated with a special focus on the microbial diversity of the AnMBR. 57% of the population was shared between the different feedstock scenarios, revealing the importance of Anaerolineaceae members besides Smithella and Methanosaeta genera. The addition of primary sludge enhanced the microbial diversity of the system during both Chlorella and Scenedesmus co-digestion and promoted different microbial structures. Aceticlastic methanogen Methanosaeta was dominant in all the feedstock scenarios. A more remarkable role of syntrophic fatty acid degraders (Smithella, Syntrophobacteraceae) was observed during co-digestion when only microalgae were digested. However, no significant changes were observed in the microbial composition during anaerobic microalgae digestion when feeding only Chlorella or Scenedesmus. This is the first work revealing the composition of complex communities for semi-continuous bioenergy production from WRRF streams. The stability and maintenance of a microbial core over-time in semi-continuous AnMBRs is here shown supporting their future application in full-scale systems for raw microalgae digestion or co-digestion.


Assuntos
Microalgas , Eliminação de Resíduos Líquidos/métodos , Biocombustíveis , Reatores Biológicos , Chlorella , Estudos Longitudinais , Microbiota , Scenedesmus
17.
Bioresour Technol ; 295: 122242, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31629282

RESUMO

Phytohormones comprise a variety of trace bioactive compounds that can stimulate cell growth and promote metabolic shifts. In the present work, a two-stage screening strategy was innovatively established to identify positive phytohormones for enhancement of astaxanthin and lipid coproduction in microplate-based cultures of mixotrophic Chromochloris zofingiensis. The results showed that auxins were the most efficient stimulators for astaxanthin accumulation. The maximum content of 13.1 mg/g and yield of 89.9 mg/L were obtained using indole propionic acid (10 mg/L) and indoleacetic acid (7.8 mg/L), representing the highest levels of astaxanthin in this microalga reported to date. Total lipids with the highest content (64.5% DW) and productivity (445.7 mg/L/d) were coproduced with astaxanthin using indoleacetic acid. Statistical analysis revealed close relations between phytohormones and astaxanthin and lipid biosynthesis. This study provides a novel original strategy for improving astaxanthin and lipid coproduction in C. zofingiensis using the selected phytohormones as positive stimulators.


Assuntos
Chlorella , Microalgas , Lipídeos , Reguladores de Crescimento de Planta , Xantofilas
18.
Bioresour Technol ; 296: 122320, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31678704

RESUMO

Thiamphenicol (TAP) is a typical medicament in animal husbandry and aquaculture for treating diverse infections. In this work, thiamphenicol biodegradation performance via microalgae was tested. The cultivation results showed that TAP could be biodegraded via the target algae. Chlorella sp. L38 presented strong adaptive ability to high concentration TAP. Biodegradation, biosorption and bioaccumulation were the dominant metabolic fates. Biodegradation contributed around 97% of the total removal efficiency at the TAP concentration of 46.2 mg·L-1. The removal of TAP by Chlorella L38 and UTEX1602 agreed with the kinetic range of zero-order reaction, and the shortest half-lives were 3.2 d and 5.0 d. Based on the identification of metabolites, the metabolic pathway of TAP by microalgae was proposed, including chlorination, chlorine substitution, dehydration and hydroxylation. Therefore, biological treatment via microalgae has the potential for TAP purification.


Assuntos
Chlorella , Microalgas , Tianfenicol , Animais , Aquicultura , Biodegradação Ambiental
19.
J Environ Manage ; 254: 109825, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31733467

RESUMO

Microalgae harvesting is one of the major bottlenecks for the production of high-value microalgal products on a large scale, which encourages investigations of harvesting methods with better cost-benefits. Among these harvesting techniques, flotation stands out as a promising method, however it is still minimally explored when compared to the sedimentation method. In this study, the pH modulation followed by dissolved air flotation (DAF) was tested as a harvesting method for Chlorella sorokiniana cultivated in wastewater. The main aims of this study were to optimize the operational parameters of coagulation (pH, velocity gradient, and mixing time) and flotation (recirculation rate), check their reproducibility and resilience with the variability of wastewater characteristics, and evaluate the final wastewater quality after treatment using an optimized harvesting method. Parameter optimization was carried out using the one-factor-at-a-time method. The optimal parameters were a velocity gradient of 500 s-1, mixing time of 30 s, pH 12, and 20% of recirculation rate. High efficiencies were obtained for C. sorokiniana removal (96.5-97.9%), making it a successful process. Moreover, the photobioreactor effluent quality was also improved significantly after microalgae harvesting, with high nutrient removal (88.6-95.1% of total Kjeldahl nitrogen and 91.8-98.3% of total phosphorus) and organic matter removal (80.5-86.8% of chemical oxygen demand). The results showed the pH modulation and DAF as an effective process for wastewater treatment and biomass harvesting. This study also indicated the importance of operational optimization, not studied until now, in which the achieved results could be potentially applied as practical guidelines for microalgae harvesting on a large scale.


Assuntos
Chlorella , Microalgas , Biomassa , Concentração de Íons de Hidrogênio , Reprodutibilidade dos Testes , Águas Residuárias
20.
Chemosphere ; 239: 124672, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31494319

RESUMO

Environmental factors such as temperature and light are the most determinants in the photosynthetic productivity in microalgae. However, under extreme of these conditions, certain resistant microalgae strains possess additional abilities such as growth in the presence of high concentrations of metals and some can improve in combinations of more than one abiotic stress. Therefore, the aim of this research was to evaluate the efficiency in photosynthetic production through the oxygen balance to variations in photon intensity, and under temperature changes in a Cd-resistant strain (DcRCd100) compared to the wild-type strain (Dc1Mwt) of Dictyosphaerium chlorelloides. The results showed that the DcRCd100 strain has the maximum efficiency at 200  µmol m-2 s-1 on photosynthesis net (Pn) (96.32 ±â€¯3.63% nmol O2 ml-1 min-1) as the threshold light saturation, and an adaptation to maintain this maximum photosynthetic gross (Pg) rate at 30 °C (94.99 ±â€¯10.03% nmol O2 ml-1 min-1) due to possible modifications in the photosynthetic apparatus that is reflected in the net evolution rate of O2 to deal with such evaluated conditions. While, Dc1Mwt strain its maximum photosynthetic efficiency was at 300 µmol m-2 s-1 and 21 °C (97.72 ±â€¯2.99 and 99.85 ±â€¯0.30%nmol O2 ml-1 min-1, respectively) and in optimal response to the oxygen balance that is normally achieved by this mesophilic genus. These results provide a new prediction of mechanisms in the oxygen evolution in photosynthesis that rules the correlation between resistance and adaptation to extreme abiotic conditions in metal resistant strains of eukaryotic microalgae.


Assuntos
Cádmio/toxicidade , Chlorella/efeitos dos fármacos , Microalgas/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Adaptação Fisiológica/fisiologia , Chlorella/crescimento & desenvolvimento , Microalgas/crescimento & desenvolvimento , Oxigênio/metabolismo , Taxa Respiratória
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