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1.
Sci Total Environ ; 729: 138666, 2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32498154

RESUMO

Cyanobacteria and microalgae are abundant biota groups in eutrophic freshwater ecosystems, serving as a food source for many aquatic organisms, including the larvae of non-biting midges (Chironomidae). Many species of cyanobacteria are toxin producers, which can act as stressors to other organisms. The present study aimed to analyze and compare the effects of dietary exposure to the common toxic cyanobacteria Anabaena sp. and non-toxic microalgae Chlorella sp. in Chironomus riparius larvae. Microcystin was detected and quantified in the methanolic extract of Anabaena sp. using the HPLC-DAD technique, and it was identified as microcystin-LR. Both Anabaena sp. and Chlorella sp. were suitable food sources to enable the survival of C. riparius larvae in laboratory conditions, causing negligible mortality and significant differences in the larval mass (ANOVA and Post hoc LSD test; p < 0.05) and hemoglobin concentration (Student's t-test; p < 0.05). Oxidative stress parameters such as advanced oxidation protein products (AOPP), thiobarbituric acid reactive substances (TBARS), catalase (CAT) and superoxide dismutase (SOD) activity, and DNA damage, were also investigated. One-way ANOVA, followed by the Post hoc LSD test, showed a significant increase in AOPP and CAT for the group of larvae fed with Chlorella sp. The same test showed moderate DNA damage in both groups of larvae, with greater damage in the group fed with Anabaena sp. Thus, Chlorella sp. and microcystin-LR producing Anabaena sp. are food sources that did not result in any drastic acute effect on the population level of C. riparius larvae. However, sub-individual-level endpoints revealed significant effects of the treatments, since they caused oxidative stress and DNA damage that may pose a danger to successive generations of test organisms.


Assuntos
Anabaena , Chironomidae , Chlorella , Animais , Ecossistema , Larva , Fitoplâncton , Poluentes Químicos da Água
2.
J Environ Manage ; 268: 110693, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32510435

RESUMO

The demand for systems that efficiently and sustainably recover value-added compounds and materials from waste streams is a major challenge. The use of wastewater as a source for recovery of carbon and nutrients is an attractive and sustainable alternative. In this study, anaerobically treated black water was treated in photobioreactors (PBRs) inoculated with Chlorella sorokiniana, and the process was investigated in terms of phosphorus and nitrogen removal, biomass growth, and the removal of pathogens. The consumption of bicarbonate (alkalinity) and acetate (volatile fatty acids) as carbon sources by microalgae was investigated. The average nutrient removal achieved was 66% for N and 74% for P. A high consumption of alkalinity (83%) and volatile organic acids (76%) was observed, which suggests that these compounds were used as a source of carbon. The biomass production was 73 mg L-1 day-1, with a mean biomass of 0.7 g L-1 at the end of the batch treatment. At the end of the experiments, a log removal/inactivation of 0.51 log for total coliforms and 2.73 log for Escherichia coli (E. coli) was observed. The configuration used, a flat-panel PBR operated in batch mode without CO2 supplementation, is a cost-effective and environmentally sustainable method for recovering of nutrients and production of algal biomass.


Assuntos
Chlorella , Microalgas , Biomassa , Escherichia coli , Nitrogênio , Nutrientes , Fósforo , Fotobiorreatores , Águas Residuárias , Água
3.
Bioresour Technol ; 310: 123472, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32388205

RESUMO

The aim of this work was to propose a novel process to make Chlorella pyrolyzed and in situ upgraded to fuel over amphiphilic SO3H-SBA-15 catalysts. This strategy is developed to build a Pickering emulsion system through the w/o (water/decalin) droplets. Chlorella catalytic pyrolysis has been conducted under the different heating rates to get the activation energy 166 kJ/mol (α = 0.5) according to the kinetic-free model. Palmitic acid, as a model compound, was employed for TG and DRIFTS analysis to elucidate the pyrolysis and deoxygenation reaction pathway. n-hexadecane pyrolysis at 3 MPa N2 illustrated the peak cracking temperature declining from thermally 422 °C to catalytically 413 °C. N2 physisorption of the fresh and post-reaction catalysts indicated that there is little catalyst decay. With improved thermal stability and hydrophobicity, the SO3H-SBA-15 catalysts showed enhanced performance for Chlorella pyrolysis, and revealed the promising application for better fuel production in aqueous conversion.


Assuntos
Chlorella , Catálise , Cinética , Pirólise , Dióxido de Silício
4.
Bioresour Technol ; 309: 123380, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32325378

RESUMO

Contamination of freshwater raceway ponds impedes the commercial cultivation of microalgae. Acclimatization of freshwater microalgae to hypersaline conditions offers a means to reduce contamination. A freshwater Chlorella species was cultured in a gradient of salinities ranging from 5 to 40‰ and pulse amplitude modulated fluorometry recorded photosynthetic functioning. While the average salinity of seawater is 35‰, optimum acclimatization occurred at 20‰, at which point the growth rate (1.6 µg chl a L-1d-1) was not significantly different from the control (1.8 µg chl a L-1d-1). The maximum relative electron transfer rate was lower (9 to 12 µmol m-2s-1) at 5 to 20‰ as compared to 40‰ (28 µmol m-2s-1) where no algal growth was recorded. ATP and NADPH were thus shunted towards synthesis of molecules that offset cytoplasmic osmotic stress. Culturing this Chlorella strain in raceway ponds under saline conditions may reduce contamination and improve productivity.


Assuntos
Chlorella , Microalgas , Aclimatação , Fluorometria , Água Doce
5.
Water Res ; 176: 115735, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32224330

RESUMO

Graphene oxide (GO) sheets are unstable in aqueous environments, and the effect of photo-transformation on GO toxicity to freshwater algae (Chlorella pyrenoidosa) was investigated. Our results demonstrated that GO underwent photo-reduction under 25-day sunlight irradiation, and the transformation was generally completed at Day 8. The toxicological investigation showed that 8-day sunlight irradiation significantly increased growth inhibition of GO (25 mg/L) to algal cells by 11.2%, due to enhanced oxidative stress and stronger membrane damage. Low molecular weight (LMW) species were produced during the 8-day GO transformation, and they were identified as two types of aromatic compounds, which played a crucial role in increasing toxicity. The combined toxicity of GO and Cu2+ ions before and after light irradiation was further investigated. Antagonistic effect was observed between the toxicity of pristine GO and co-existing Cu2+ ions. After co-irradiation of GO and Cu2+ ions for 8 days, their combined toxicity was unexpectedly lower or insignificant in comparison with the treatments of pristine GO, or pristine GO in the presence of Cu2+ ions. Two mechanisms were revealed for this finding: (1) Cu2+ ions suppressed the photo-transformation of GO; (2) the toxicity of free Cu2+ ions was decreased through the adsorption/retention of Cu2+ ions and formation of Cu-based nanoparticles (e.g., Cu2O and Cu2S) on the photo-transformed GO. The provided data are helpful for better understanding the environmental process and risk of GO under natural conditions.


Assuntos
Chlorella , Grafite , Poluentes Químicos da Água , Água Doce , Íons , Metais
6.
Bioresour Technol ; 307: 123253, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32244074

RESUMO

A single helical baffle (SHB), consisting of twisted turns, was developed to convert straight flow into spiral flow in a Chlorella PY-ZU1 open raceway pond (ORWP) bubbled with 15% CO2. Microalgal solution flowing through the SHB alternative helical interspaces generated whirling flow both vertically and horizontally, which decreased mixing and increased mass transfer rates. The optimized SHB had a pitch length to total SHB length ratio of 0.13 and SHB diameter to ORWP single channel width ratio of 0.30, which decreased mixing times and increased mass transfer coefficients by 41.1% and 38.4% respectively. SHB moved Chlorella PY-ZU1 from the ORWP bottom to the top, increasing light exposure for photosynthesis. Cellular electron transfer rates and photochemical efficiency (φPSII) increased by 18%, chlorophyll a content increased by 16% and variable to maximum fluorescence ratio increased by 13%. The microalgal biomass of SHB ORWP was 23% higher than that of conventional ORWP.


Assuntos
Chlorella , Microalgas , Biomassa , Dióxido de Carbono , Clorofila A
7.
Bioresour Technol ; 308: 123292, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32278995

RESUMO

In the present work Chlorella pyrenoidosa, Scenedesmus abundans and Anabaena ambigua have been evaluated for their biomass, phycoremediation efficiency and biomethane production potential by cultivating them in the primary treated sewage waste water (PTSWW) under controlled conditions. By the end of 25-day experiment, up to 52-88% reduction was observed in the nutrient concentration from the 3:1 ratio of PTSWW. Co-digestion of microalgal biomass (dry) with cow dung was performed to estimate biomethane potential. Biogas yield of 618-925 ml g-1 VS with 48-65% of methane content was obtained employing the microalgal species cultivated in PTSWW. Microalgae appeared notably competent at nutrient sequestration from PTSWW with significant microalgal biomass productivity for biogas production. Energy balance studies revealed the feasibility of coupling the remediation with energy generation. High photosynthetic rate and biomass generation ability along with nutrient confiscation supports employment of microalgae as a potential next generation biofuel source with waste management.


Assuntos
Chlorella , Microalgas , Animais , Biocombustíveis , Biomassa , Bovinos , Emprego , Estudos de Viabilidade , Feminino , Esgotos , Águas Residuárias
8.
Bioresour Technol ; 307: 123233, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32240927

RESUMO

This work evaluated the potential of microalgae of Chlorella sp., SL7A, Chlorococcum sp., SL7B and Neochloris sp.,SK57 cultivated in river water contaminated with pharmaceutical effluent for biomass and lipid production. It has been observed that fast growing algae in this medium is Neochloris sp.SK57. Maximum biomass and lipid yield was obtained from Neochloris sp. SK57 (0.52 g/l) and Chlorococcum sp. SL7B (0.129 g/l)along with drycell weight of lipid was 28%.The increased in biomass and lipid in this media is could due to assimilation of organic nutrients and stress due to other components present in the river water. Fatty acid profile of algal biomass showed that saturated fatty acids production is enhanced in oils of Neochloris sp. SK57, and its suitability in food and fuel applications. Water quality of the river water was monitored before and after algal cultivation. Results showed that quality of river water was improved after algal cultivation.


Assuntos
Chlorella , Microalgas , Preparações Farmacêuticas , Biodegradação Ambiental , Biocombustíveis , Biomassa , Rios
9.
Bioresour Technol ; 310: 123403, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32339891

RESUMO

The reduction of resource requirements for the outdoor cultivation of Chlorella sorokiniana using 180 L flat panel photobioreactors through medium recycling was investigated in this study. Without medium recycling, algae grew in 13.6 d from 0.92 to 5.32 gL-1with a productivity of 0.32 gL-1d-1. For the production of 748 g algae dry weight (DW), 152gkg-1 N, 27 gkg-1 P and 231 Lkg-1 water were needed. A realistic cultivation model with the recycling of medium and a productivity of 0.4 gL-1d-1 was set up based on experimental data, in which the requirements decreased to 104gkg-1 N, 24 gkg-1 P and 141 Lkg-1 water. Compared to the production of lutein-containing plant Tagetes erecta, water and potassium requirements of up to 91% less and 96% respectively and higher biomass productivity by the factor 3.7 was achieved.


Assuntos
Chlorella , Microalgas , Biomassa , Fotobiorreatores , Reciclagem
10.
Chemosphere ; 251: 126406, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32151805

RESUMO

Immobilized microalgae have great potential on the nutrient removal during wastewater treatment. However, their applications are challenged by how to cost-effectively maintain and preserve large number of viable and active microalgal cells. In this study, the cells of Chlorella sacchrarophila were immobilized in the agar containing with algal nutrient, encapsulated in a transparent package and preserved at room temperature. After the preservation for 200 days, microalgal cells with viability of 47-52% were maintained and could be quickly revived after the cultivation in fresh algal medium. Based on the agar-immobilized microalgae, the NH4+-N and PO43--P were efficiently removed from batch and continuous cultures, with the highest removal efficiencies ranging from 96% to 99% were observed. Even being recycled for eight times, the agar-immobilized microalgae were still able to remove 94% of NH4+-N and 66% of PO43--P. Moreover, more than 60% of the nutrient removal efficiency was determined even the agar-immobilized microalgae being preserved for 120 days at room temperature. This work provides a simple, cost-effective and practicable method for the long-term preservation of microalgae at room temperature, which makes the application of microalgal species on the nutrient removal during wastewater treatment more convenient and useful.


Assuntos
Chlorella/fisiologia , Fósforo/metabolismo , Ágar , Biodegradação Ambiental , Biomassa , Microalgas , Nitrogênio , Temperatura , Águas Residuárias
11.
Water Res ; 175: 115656, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32145399

RESUMO

Microalgae-mediated biodegradation of antibiotics has recently gained increased attention from international scientific community. However, limited information is available regarding microalgae-mediated biodegradation of SMX in a co-metabolic system. Here we investigated the biodegradation of sulfamethoxazole (SMX) by five algal species (Pseudokirchneriella subcapitata, Scenedesmus quadricauda, Scenedesmus obliquus, Scenedesmus acuminatus and Chlorella pyrenoidosa), and its transformation pathways by C. pyrenoidosa in a sodium acetate (3 mM) co-metabolic system. The results showed that the highest SMX dissipation (14.9%) was detected by C. pyrenoidosa after 11 days of cultivation among the five tested algal species in the absence of other carbon sources. The addition of sodium acetate (0-8 mM) significantly enhanced the dissipation efficiency of SMX (0.4 µM) from 6.05% to 99.3% by C. pyrenoidosa after 5 days of cultivation, and the dissipation of SMX followed the first-order kinetic model with apparent rate constants (k) ranging from 0.0107 to 0.9811 d-1. Based on the results of mass balance analysis, biodegradation by C. pyrenoidosa was the main mechanism for the dissipation of SMX in the culture medium. Fifteen phase I and phase II metabolites were identified, and subsequently the transformation pathway was proposed, including oxidation, hydroxylation, formylation and side chain breakdown, as well as pterin-related conjugation. The majority of metabolites of SMX were only observed in the culture medium and varied with cultivation time. The findings of the present study showed effective co-metabolism of a sulfonamide by microalgae, and it may be applied in the aquatic environment remediation and wastewater treatment in the future.


Assuntos
Chlorella , Microalgas , Scenedesmus , Água Doce , Sulfametoxazol
12.
Water Res ; 174: 115622, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32145554

RESUMO

The sulfate radical (•SO4-)-based advanced oxidation processes (AOPs) for the degradation of refractory organic pollutants consume a large amount of persulfate activators and often generate toxic organic by-products. In this study, we proposed a novel iron-cycling process integrating •SO4--based AOP mediated by reusable iron particles and a sulfidogenic process to degrade and detoxify Orange II completely. The rusted waste iron particles (Fe0@FexOy), which contained FeII/FeIII oxides (FexOy) on the shell and zero-valent iron (Fe0) in the core, efficiently activated persulfate to produce •SO4- and hydroxyl radicals (•OH) to degrade over 95% of Orange II within 120 min. Both •SO4- and •OH destructed Orange II through a sequence of electron transfer, electrophilic addition and hydrogen abstraction reactions to generate several organic by-products (e.g., aromatic amines and phenol), which were more toxic than the untreated Orange II. The AOP-generated organic by-products were further mineralized and detoxified in a sulfidogenic bioreactor with sewage treatment together. In a 170-d trial, the organic carbon removal efficiency was up to 90%. The inhibition of the bioreactor effluents on the growth of Chlorella pyrenoidosa became negligible, due to the complete degradation and mineralization of toxic AOP-generated by-products by aromatic-degrading bacteria (e.g., Clostridium and Dechloromonas) and other bacteria. The sulfidogenic process also well recovered the used Fe0@FexOy particles through the reduction of surface FeIII back into FeII by hydrogen sulfide formed and iron-reducing bacteria (e.g., Sulfurospirillum and Paracoccus). The regenerated Fe0@FexOy particles had more reactive surface FeII sites and exhibited much better reactivity in activating persulfate in at least 20 reuse cycles. The findings demonstrate that the integrated process is a promising solution to the remediation of toxic and refractory organic pollutants because it reduces the chemical cost of persulfate activation and also completely detoxifies the toxic by-products.


Assuntos
Chlorella , Poluentes Químicos da Água , Compostos Azo , Benzenossulfonatos , Ferro , Oxirredução , Sulfatos
13.
Chemosphere ; 252: 126465, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32199165

RESUMO

The role of dissolved organic matter (DOM) on the biochemical behavior and toxicity of heavy metals in water is very important but complex and unclear. The present work extracted DOM from a natural water and separated it into three fractions, namely humic acid (HA), fulvic acid (FA) and transphilic acid (TPA). Optical detection showed that HA had most aromatic ring skeletons, FA had more aromatic ring hydrophilic groups, and TPA had the largest number of hydroxyl or carboxyl groups. Their effects on the toxicity of Cu by Chlorella pyrenoidosa depended on types and concentration of DOM. In the case of algal exposure to 0.003 mM initial Cu concentration, the final algal optical density increased from 0.317 of the control group to 0.345, 0.645 and 0.435 in the presence of 20, 10 mg L-1 HA, and 10 mg L-1 TPA, respectively, but were suppressed to 0.246, 0.117 and 0.234 in the presence of 10, 20 mg L-1 FA and 20 mg L-1 TPA. Most adsorption isotherms lost the linearity in the presence of HA, FA and TPA. The adsorbed Cu increased from 0.242 to 0.477 mmol g-1, following the order of increased concentration of HA, FA, and TPA. The formation of ternary complex and the multi-layer adsorption were proposed to explain the significant enhancement adsorption of Cu in the presence of FA and TPA. This study showed that the type and the density of effective functional groups in DOM determined its effects on Cu toxicity and bioavailability to algae.


Assuntos
Chlorella/metabolismo , Cobre/metabolismo , Poluentes Químicos da Água/metabolismo , Adsorção , Benzopiranos , Disponibilidade Biológica , Substâncias Húmicas , Metais Pesados
14.
Ecotoxicol Environ Saf ; 195: 110484, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32200150

RESUMO

Microplastics and nonylphenol (NP) are considered as emerging pollutant and have attracted wide attention, while their combined toxicity on aquatic organisms is barely researched. Therefore, the combined toxicity influence of NP with three types of microplastics containing polyethylene (PE1000, 13 µm and PE, 150 µm), polyamide (PA1000, 13 µm and PA, 150 µm) polystyrene (PS, 150 µm) on microalgae Chlorella pyrenoidosa was analyzed. Both growth inhibition, chlorophyll fluorescence, superoxide dismutase (SOD), malondialdehyde (MDA), and catalase (CAT) were determined. We found that single microplastics and NP both inhibited algal growth, thereby causing oxidative stress. The order of inhibition effect in single microplastics experiment was PE1000 > PA1000 > PE ≈ PS > PA. The combined toxicity experiment results indicated that the presence of microplastics had positive effect in terms of alleviating NP toxicity to C. pyrenoidosa, and the microplastics adsorption capacity to NP was the dominant contributing factor for this effect. According to the independent action model, the combined toxicity was antagonistic. Because the negative effect of smaller size microplastics on algal growth was aggravated with prolonged exposure time, the optimum effect of microplastics alleviated NP toxicity was PA1000 at 48 h, while this effect was substituted by PA at 96 h during combined toxicity. Thus, the toxicity of smaller size microplastics has a nonnegligible influence on combined toxicity. This study confirms that microplastics significantly affected the toxicity of organic pollutants on microalgae. Further research on the combined toxicity of smaller size microplastics with pollutants in chronic toxicity is needed.


Assuntos
Chlorella/efeitos dos fármacos , Microplásticos/toxicidade , Fenóis/toxicidade , Poluentes Químicos da Água/toxicidade , Adsorção , Catalase/metabolismo , Chlorella/enzimologia , Chlorella/metabolismo , Interações Medicamentosas , Malondialdeído/metabolismo , Microalgas/efeitos dos fármacos , Microalgas/enzimologia , Microalgas/metabolismo , Microplásticos/química , Estresse Oxidativo , Poliestirenos/toxicidade , Superóxido Dismutase/metabolismo , Poluentes Químicos da Água/química
15.
Chemosphere ; 248: 126101, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32045977

RESUMO

Calcium decline and cyanobacterial blooms pose a serious threat to the crustacean zooplankton Daphnia, which has a high demand for calcium. In the present study, we exposed two different clones of Daphnia pulex to different combinations of calcium concentrations (0.1, 0.5, 1.0, 5.0, 10.0 mg L-1) and food types (100% Chlorella; 80% Chlorella and 20% non-toxic Microcystis; 80% Chlorella and 20% toxic Microcystis) for 16 days, recorded the key life-history traits, and then used an exponential rise function to fit the traits. Results showed toxic Microcystis and low calcium together negatively affected the survival, development, and reproduction of Daphnia. The negative effect of non-toxic Microcystis and low calcium only affected the development and reproduction. The survival time and reproductive performance increased exponentially with increasing calcium concentration and then approached an asymptotic maximum. Both non-toxic and toxic Microcystis reduced the asymptotic maximum of the reproductive performance. The rising rate at which they reached the asymptotes differed significantly among the three food types; i.e., the reproductive performance of Daphnia was affected in a wider range of calcium concentrations under bad food quality. The findings indicated that Microcystis impaired the tolerance of Daphnia to low calcium, which may cause serious consequences in freshwater ecosystems.


Assuntos
Adaptação Fisiológica/efeitos dos fármacos , Cálcio/metabolismo , Daphnia/efeitos dos fármacos , Traços de História de Vida , Toxinas Marinhas/toxicidade , Microcystis/metabolismo , Zooplâncton/efeitos dos fármacos , Animais , Cálcio/farmacologia , Chlorella/metabolismo , Relação Dose-Resposta a Droga , Ecossistema , Água Doce/química , Toxinas Marinhas/metabolismo , Microcystis/crescimento & desenvolvimento , Reprodução/efeitos dos fármacos
16.
Bioresour Technol ; 302: 122814, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32004812

RESUMO

Swine wastewater is rich in nitrogen and organic carbon which are essential macronutrients for microalgal growth. Three indigenous microalgal strains (Chlorella sorokiniana AK-1, Chlorella sorokiniana MS-C1, and Chlorella sorokiniana TJ5) were examined for their growth capability in untreated swine wastewater. C. sorokiniana AK-1 showed the best tolerance towards swine wastewater, and obtained the highest biomass concentration (5.45 g/L) and protein productivity (0.27 g/L/d) when grown in 50% strength swine wastewater. Cell immobilization using sponge as the solid carrier further enhanced maximal biomass concentration and protein productivity to 8.08 g/L and 0.272 g/L/d, respectively. Reuse of microalgae loaded sponge resulted in an average biomass production and protein productivity of 6.51 g/L and 0.15 g/L/d, respectively. The COD, TN and TP removal efficiency for the swine wastewater was 90.1, 97.0 and 92.8%, respectively. This innovative swine wastewater treatment method has demonstrated excellent performance on simultaneous swine wastewater treatment and protein-rich microalgal biomass production.


Assuntos
Chlorella , Microalgas , Animais , Biomassa , Nitrogênio , Suínos , Águas Residuárias
17.
Bioresour Technol ; 302: 122840, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32014729

RESUMO

Herein, a two-stage cultivation process was devised to overcome low pigment content of algal biomass grown in heterotrophy. Post-treatment conditions (i.e., light intensity, temperature, pH and salinity) were initially tested for dense heterotrophically-grown Chlorella sp. HS2 cultures in a multi-channel photobioreactor (mcPBR), and the results clearly indicated the influence of each abiotic factor on algal pigment production. Subsequently, the optimal post-treatment conditions (i.e., 455 µmol m-2 s-1, 34.8℃, pH 8.23 and 0.7% (w/v) salinity), in which highest accumulation of algal pigments is expected, were identified using Response Surface Methodology (RSM). Compared to the control cultures grown in mixotrophy for the same duration of entire two-stage process, the results indicated a significantly higher pigment productivity (i.e., 167.5 mg L-1 day-1) in a 5-L fermenter following the post-treatment at optimal conditions. Collectively, these results suggest that the post-treatment of heterotrophic cultures can be successfully deployed to harness the nascent algae-based bioeconomy.


Assuntos
Chlorella , Processos Heterotróficos , Biomassa , Fotobiorreatores , Salinidade
18.
Bioresour Technol ; 302: 122879, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32028148

RESUMO

A cost-effective and environmentally friendly method for biofuel production was developed, by utilizing duckweed as feedstock for biohydrogen production through dark fermentation and simultaneously using the fermentative waste to produce microalgal lipids. The results suggested that acid hydrolysis (1% H2SO4) was more suitable for the pretreatment of duckweed biomass. Maximum hydrogen production of 169.30 mL g-1 dry weight was determined under a temperature of 35 °C and an initial pH of 7.0. After the dark fermentation, the volatile fatty acids (VFAs) including acetate and butyrate, were detected in the waste, with concentration determined as 1.04 g L-1 and 1.52 g L-1, respectively. During the mixotrophic cultivation of Chlorella sacchrarophila FACHB-4 using waste as feedstock, the maximum microalgal biomass and the lipid productions were about 2.8 and 33 times higher with respect to the autotrophic growth. The simultaneous biohydrogen production and waste utilization method provided a green strategy for biofuel production.


Assuntos
Chlorella , Microalgas , Biocombustíveis , Biomassa , Fermentação , Hidrogênio , Lipídeos
19.
Sci Total Environ ; 715: 136775, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32040991

RESUMO

Hydrothermal Liquefaction (HTL) could be a promising and better alternative to other techniques for energy recovery from municipal sewage sludge (MSS). However, the nutrients (i.e., N, and P) recovery potential from the byproducts, generated in the HTL of MSS, needs to be studied so that a comprehensive sludge management practice could be adopted. In this study, HTL process temperature (275-400 °C), and reaction time (30-120 min) were first investigated for biocrude yield and release of the nutrients to the aqueous phase liquid (APL) and biochar. The maximum energy recovery (i.e., 59%) and maximum energy return on investment (i.e., 3.5) were obtained at 350 °C and 60 min of holding time. With the increase in HTL reaction time, the concentration of nitrogen in the APL increased (5.1 to 6.8 mg/L) while the concentration of phosphorus decreased (0.89 to 0.22 mg/L); the opposite was observed for the biochar. The nutrient recycling efficiency from the APL using microalgae was found to be strain-specific; nitrogen recycling efficiency by Picochlorum sp. and Chlorella sp. were 95.4 and 58.6%, respectively. The APL, derived from 1 kg MSS, could potentially produce 0.49 kg microalgal biomass. Since the concentrations of various metals in the biochar samples were substantially lower compared to their concentrations in raw MSS, the application of biochar as a soil conditioner could be very promising. Overall, net positive energy could be recovered from MSS using the HTL process, while the nutrients in the APL could be used to cultivate specific microalgae, and biochar could be applied to enhance the soil quality.


Assuntos
Esgotos , Chlorella , Microalgas , Nutrientes , Reciclagem , Temperatura
20.
Ecotoxicol Environ Saf ; 192: 110263, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32036098

RESUMO

Despite concentrations often fluctuating in aquatic systems that receive contaminant inputs, there has only been a relatively small number of studies investigating the toxicity of intermittent exposures. This is particularly the case for industrial and mine effluents that may contain complex mixtures of contaminants and other stressors. The lack of information is impeding the regulation of such contaminant exposures, whose risk is often assessed by comparison to continuous exposures in whole effluent toxicity (direct toxicity assessment) testing. The current study compared the toxicity from continuous (72-h) and pulsed (1- to 48-h) exposures of two neutralised mine waters (NMWs) to the freshwater algae, Chlorella sp. When the algal toxicity of the different exposures was related to the time-averaged concentration (TAC) of contaminants, it was found that the TAC was a good predictor of toxicity in any given test, with variability in toxicity between tests mainly related to differences in contaminant concentrations from the neutralisation of the acidic mine waters. When the data from tests on two samples were combined on a whole-effluent TAC basis, the EC50 values (95% confidence intervals) for the continuous and pulsed exposures were 0.68% (0.36-1.3) and 0.63% (0.38-1.1) respectively, for NMW sample one, while the corresponding EC50 values for NMW sample two were 1.3% (1.0-1.7) and 1.9% (1.6-2.2), respectively. The toxicity of the second water was strongly influenced by the zinc, and probably copper, concentrations, while the toxicity of the first appeared to be related to additive or synergistic toxicity from Al, Cd, Mn and Pb. The findings are discussed in relation to using a contaminant TAC-approach to revise water quality guideline values derived for continuous exposures for application to pulsed exposures, where higher concentrations may be permissible for short durations.


Assuntos
Chlorella/efeitos dos fármacos , Mineração , Poluentes Químicos da Água/toxicidade , Animais , Cobre/toxicidade , Metais/toxicidade , Qualidade da Água , Zinco/toxicidade
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