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1.
J Environ Manage ; 263: 110353, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883472

RESUMO

Nowadays, as the world population is in need of creating alternative materials that can replace conventional plastics, microalgae biomass may be identified as a viable source for producing more environmentally friendly materials. Scenedesmus sp and Desmodesmus sp are the main components (~80%) of a microalgae consortium (MC) that first has been used to remove Nitrogen and Phosphorus from wastewater. The potential to develop bioplastic materials from MC considering its relatively high protein content (~48%) has been assessed in the present manuscript, using as a reference a commercial biomass rich an Arthrospira specie (AM) also present in the studied consortium. Bioplastics were obtained through injection moulding of blends obtained after mixing with different amounts of glycerol, and eventually characterized using Dynamic Mechanical Thermal Analysis (DMTA), water immersion and tensile tests. All bioplastics displayed a glass transition temperature around 60 °C, showing a thermoplastic behavior which is less pronounced in the CM based bioplastics. This would imply a greater thermal resistance of bioplastics produced from the biomass harvested in wastewater. Moreover, these bioplastics showed a lower ability to absorb water when immersed, due to the lower deformability displayed in the tensile tests. The mechanical properties of all samples, independently of the nature of the biomass, were improved when the presence of the biomass was higher. Therefore, results here presented prove the potential of valorisation of microalgae consortia used in the effective treatment of wastewater through the development of bioplastic materials.


Assuntos
Microalgas , Scenedesmus , Biomassa , Nitrogênio/análise , Fósforo , Águas Residuárias
2.
Nat Commun ; 11(1): 3831, 2020 07 31.
Artigo em Inglês | MEDLINE | ID: mdl-32737305

RESUMO

Long-term time series have provided evidence that anthropogenic pressures can threaten lakes. Yet it remains unclear how and the extent to which lake biodiversity has changed during the Anthropocene, in particular for microbes. Here, we used DNA preserved in sediments to compare modern micro-eukaryotic communities with those from the end of the 19th century, i.e., before acceleration of the human imprint on ecosystems. Our results obtained for 48 lakes indicate drastic changes in the composition of microbial communities, coupled with a homogenization of their diversity between lakes. Remote high elevation lakes were globally less impacted than lowland lakes affected by local human activity. All functional groups (micro-algae, parasites, saprotrophs and consumers) underwent significant changes in diversity. However, we show that the effects of anthropogenic changes have benefited in particular phototrophic and mixotrophic species, which is consistent with the hypothesis of a global increase of primary productivity in lakes.


Assuntos
DNA/genética , Eucariotos/genética , Sedimentos Geológicos/análise , Lagos/análise , Alveolados/classificação , Alveolados/genética , Alveolados/isolamento & purificação , Biodiversidade , Evolução Biológica , Ecossistema , Eucariotos/classificação , Eucariotos/isolamento & purificação , História do Século XIX , História do Século XX , História do Século XXI , Atividades Humanas/história , Humanos , Microalgas/classificação , Microalgas/genética , Microalgas/isolamento & purificação , Microbiota/genética , Processos Fototróficos/fisiologia , Rhizaria/classificação , Rhizaria/genética , Rhizaria/isolamento & purificação , Estramenópilas/classificação , Estramenópilas/genética , Estramenópilas/isolamento & purificação
3.
Environ Pollut ; 265(Pt B): 114579, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32806438

RESUMO

The present study evaluated the capacity of a semi-closed, tubular horizontal photobioreactor (PBR) to remove pesticides from agricultural run-off. The study was carried out in summer (July) to study its efficiency under the best conditions (highest solar irradiation). A total of 51 pesticides, including 10 transformation products, were selected and investigated based on their consumption rate and environmental relevance. Sixteen of them were detected in the agricultural run-off, and the estimated removal efficiencies ranged from negative values, obtained for 3 compounds, namely terbutryn, diuron and imidacloprid, to 100%, achieved for 10 compounds. The acidic herbicide MCPA was removed by 88% in average, and the insecticides 2,4-D and diazinon showed variable removals, between 100% and negative values. The environmental risk associated to the compounds still present in the effluent of the PBR was evaluated using hazard quotients (HQs), calculated using the average and highest measured concentrations of the compounds. HQ values > 10 (meaning high risk) were obtained for imidacloprid (21), between 1 and 10 (meaning moderate risk) for 2,4-D (2.8), diazinon (4.6) and terbutryn (1.5), and <1 (meaning low risk) for the remaining compounds diuron, linuron and MCPA. The PBR treatment yielded variable removals depending on the compound, similarly to conventional wastewater treatment plants. This study provides new data on the capacity of microalgae-based treatment systems to eliminate a wide range of priority pesticides under real/environmental conditions.


Assuntos
Microalgas , Praguicidas/análise , Poluentes Químicos da Água/análise , Biodegradação Ambiental , Água
4.
Mar Pollut Bull ; 158: 111403, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32753188

RESUMO

Effects of nanoplastics at low level on the marine primary producer are largely unclear. To assess the potential risk of nanoplastic pollution, this study exposed marine green microalgae Platymonas helgolandica to 20, 200, and 2000 µg/L 70-nm polystyrene nanoplastics for 6 days. Nanoplastics significantly inhibited the growth of P. helgolandica during the first 4 days of exposure, and elevated heterocyst frequency was observed in 200 and 2000 µg/L exposure groups in the early exposure stage. Exposure to 200 and 2000 µg/L nanoplastics for 4 days increased the membrane permeability and mitochondrial membrane potential, and decreased light energy used in photochemical processes of microalgae. Moreover, clear morphological changes, including surface folds, fragmentation, aggregation cluster, and rupture, in the microalgae exposed to nanoplastics were observed under scanning electron microscope and transmission electron microscope. These results demonstrate that nanoplastics could reduce the microalgal vitality by the damage on cell morphology and organelle function.


Assuntos
Clorófitas , Microalgas , Poluentes Químicos da Água , Poliestirenos
5.
J Environ Manage ; 271: 111041, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32778320

RESUMO

Lipid production in microalgae under nitrogen (N) starved condition can be enhanced by excess phosphorus (P) supply in the second stage of two-stage cultivation strategy. However, implementing two-stage cultivation is difficult in large-scale cultivation system as it requires high energy of transferring large algal biomass from first stage to second stage. To address this problem, we have optimized a continuous two-stage (CTS) cultivation strategy using Chlorella sp. HS2, where nitrogen in the growth environment is depleted naturally via consumption. To enhance both biomass and lipid productivity this strategy explored supplementation of additional P from 50% to 2500% of the initial concentration at the start of N-limited second stage of growth. The results of the optimization study in photobioreactor (PBR) showed that supplementing 500% of initial P and 100% of initial other nutrients (O) (N0-P500-O100) on 5th day showed the maximum biomass productivity of 774.4 mg L-1 d-1. It was observed that Chlorella sp. HS2 grown in PBR yielded higher biomass (3.8 times), lipid (6.1 times) and carbohydrate (5.5 times) productivity in comparison to the open raceway ponds (ORP) study, under optimum nutrient and carbon supply condition. The maximum lipid (289.6 mg L-1 d-1) and carbohydrate (219.2 mg L-1 d-1) productivities were obtained in TPBR-3, which were 1.9 and 1.3 times higher than that of TPBR-2 (+ve control) and 9.6 and 3.7 times higher than that of TPBR-1 (-ve control), respectively. Fatty acid mainly composed of C16/C18 (84.5%-85.7%), which makes the microalgal oil suitable for biofuel production. This study concluded that feeding excess amount of P is an effective and scalable strategy to improve the biomass and lipid productivity of CTS cultivation.


Assuntos
Chlorella , Microalgas , Biocombustíveis , Biomassa , Fósforo , Fotobiorreatores
6.
Sci Total Environ ; 737: 140275, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32783858

RESUMO

Traditional autotrophic microalgae exhibit low rates of organic carbon assimilation and conversion to useful compounds when switching to mixotrophic or heterotrophic growth. The goal of this study was to investigate the effect of inorganic carbon limitation on the efficiency of organic carbon (glycerol) assimilation and conversion to total fatty acids (TFAs) or the long-chain polyunsaturated fatty acid eicosapentaenoic acid (EPA). An oleaginous Monodus subterraneus was selected and six cultivation conditions were set, including Autotrophy-no aeration, Autotrophy-aeration, Mixotrophy-no aeration, Mixotrophy-no aeration & no Na2CO3, Mixotrophy-aeration, and Heterotrophy. The results showed M. subterraneus could utilize glycerol and grow under mixotrophic condition, while it was not occurred under heterotrophy. Superiority of mixotrophy to autotrophy on biomass productivity was more obvious under inorganic carbon limitation (no aeration or no Na2CO3) than inorganic carbon supply (aeration and existing Na2CO3 in the medium). CO2 limitation (no aeration) decreased content (of dry weight) and production (in medium) of TFAs, which was not evident in mixotrophy. CO2 limitation and inorganic carbon substrate stress largely improved the COD yield of TFAs and EPA under mixotrophic condition. TFA yield (%COD) under Mixotrophy-no aeration & no Na2CO3 was maximum (22.82%), and was almost two-fold higher than that under Mixotrophy-no aeration and nearly three-fold higher than that with Mixotrophy-aeration. EPA yield (% COD) under mixotrophy-no aeration & no Na2CO3 was maximum (6.58%). These results suggested that inorganic carbon limitation is a potentially useful method to enhance conversion of organic carbon to TFAs. Furthermore, the results suggest an application to obtain high value compounds (TFAs or EPA) combined with a high assimilation rate of waste glycerol from biodiesel and epichlorohydrin production by microalgae.


Assuntos
Microalgas , Estramenópilas , Biomassa , Carbono , Ácidos Graxos , Processos Heterotróficos
7.
Water Sci Technol ; 81(10): 2127-2139, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32701491

RESUMO

Membrane fouling mechanisms of the filtration of a mixed-culture microalgal biomass grown in real wastewater were investigated using crossflow filtration experiments. The results of flux measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses for three membranes, two microfiltration (PES01 and PES003) and one ultrafiltration (UC030), showed that the UC030 membrane may be more appropriate for microalgae harvesting due to its higher steady flux rate and lower flux reduction during filtration compared to the initial flux (44% for UC030, compared to 86% for PES01 and 79% for PES003). It was also observed that the membrane resistance due to concentration polarization was the dominant membrane resistance in this study for all three membranes, constituting about 67%, 61% and 51% for PES01, PES003, and UC030, respectively. The next largest membrane resistance was provided by pore blocking, while the resistance provided by cake formation was found to be very small for all membranes (3%, 15% and 18% for PES01, PES003 and UC030, respectively), which were also supported by SEM and AFM analyses.


Assuntos
Microalgas , Biomassa , Filtração , Membranas Artificiais , Ultrafiltração , Águas Residuárias
8.
Bioresour Technol ; 313: 123743, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32620368

RESUMO

Nitrite removal is necessary and significant for pickle and meat processing wastewater. In this study, Chlorella sp. L38 is used as an alternative to remove nitrite and reuse it as nitrogen source for potential value-added ingredients production. Based on the typical BG11 medium with and without NaNO3 (which is the conventional nitrogen source), nitrite is additionally provided, and its concentration gradient was set at 0, 50, 100, 150 and 200 µmol/L, respectively. The experimental results showed that the nitrite removal rate could achieve 57.1 µmol/L/d. In addition, the biomass variation, and value-added ingredients (polysaccharides, lipid, and protein) productivity were also measured, and their yield could achieve 4.8 mg/g/d, 3.0 mg/L/d and 5.5 mg/L/d, respectively. It indicated that Chlorella sp. L38 has the potential to be an environmentally friendly approach for nitrite removal of wastewater.


Assuntos
Chlorella , Microalgas , Biomassa , Nitritos , Nitrogênio , Águas Residuárias
9.
Aquat Toxicol ; 226: 105551, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32707232

RESUMO

Strains of microalgae vary in traits between species and populations due to adaptation or stochastic processes. Traits of individual strains may also vary depending on the acclimatization state and external forces, such as abiotic stress. In this study we tested how metal tolerance differs among marine diatoms at three organizational levels: species, populations, and strains. At the species level we compared two pelagic Baltic Sea diatoms (Skeletonema marinoi and Thalassiosira baltica). We found that the between-species differences in tolerance (EC50) to the biologically active metals (Cu, Co, Ni, and Zn) was similar to that within-species. In contrast, the two species differed significantly in tolerance towards the non-essential metals, Ag (three-fold higher in T. baltica), Pb and Cd (two and three-fold higher in S. marinoi). At the population level, we found evidence that increased tolerance against Cu and Co (17 and 41 % higher EC50 on average, respectively) had evolved in a S. marinoi population subjected to historical mining activity. On a strain level we demonstrate how the growth phase of cultures (i.e., cellular densities above exponential growth) modulated dose-response relationships to Ag, Cd, Co, Cu, and Zn. Specifically, the EC50's were reduced by 10-60 % in non-exponentially growing S. marinoi (strain RO5AC), depending on metal. For the essential metals these differences were often larger than the average differences between the two species and populations. Consequently, without careful experimental design, interactions between nutrient limitation and metal stress may interfere with detection of small, but evolutionary and ecologically important, differences in tolerance between microalgae. To avoid such artifacts, we outline a semi-continuous cultivation approach that maintains, and empirically tests, that exponential growth is achieved. We argue that such an approach is essential to enable comparison of population or strain differences in tolerance using dose-response tests on cultures of microalgae.


Assuntos
Aclimatação/efeitos dos fármacos , Diatomáceas/crescimento & desenvolvimento , Metais Pesados/toxicidade , Microalgas/crescimento & desenvolvimento , Poluentes Químicos da Água/toxicidade , Diatomáceas/efeitos dos fármacos , Microalgas/efeitos dos fármacos , Mineração , Dinâmica Populacional , Especificidade da Espécie
10.
Water Res ; 182: 116038, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32619685

RESUMO

Forward osmosis (FO) has great potential for low energy consumption wastewater reuse provided there is no requirement for draw solutes (DS) regeneration. Reverse solute flux (RSF) can lead to DS build-up in the feed solution. This remains a key challenge because it can cause significant water flux reduction and lead to additional water quality problems. Herein, an osmotic photobioreactor (OsPBR) system was developed to employ fast-growing microalgae to consume the RSF nutrients. Diammonium phosphate (DAP) was used as a fertilizer DS, and algal biomass was a byproduct. The addition of microalgae into the OsPBR proved to maintain water flux while reducing the concentrations of NH4+-N, PO43--P and chemical oxygen demand (COD) in the OsPBR feed solution by 44.4%, 85.6%, and 77.5%, respectively. Due to the forward cation flux and precipitation, intermittent supplements of K+, Mg2+, Ca2+, and SO42- salts further stimulated algal growth and culture densities by 58.7%. With an optimal hydraulic retention time (HRT) of 3.33 d, the OsPBR overcame NH4+-N overloading and stabilized key nutrients NH4+-N at âˆ¼ 2.0 mg L-1, PO43--P < 0.6 mg L-1, and COD < 30 mg L-1. A moderate nitrogen reduction stress resulted in a high carbohydrate content (51.3 ± 0.1%) among microalgal cells. A solids retention time (SRT) of 17.82 d was found to increase high-density microalgae by 3-fold with a high yield of both lipids (9.07 g m-3 d-1) and carbohydrates (16.66 g m-3 d-1). This study encourages further exploration of the OsPBR technology for simultaneous recovery of high-quality water and production of algal biomass for value-added products.


Assuntos
Microalgas , Purificação da Água , Biomassa , Membranas Artificiais , Nutrientes , Osmose , Fotobiorreatores , Águas Residuárias
11.
Gene ; 757: 144929, 2020 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-32622990

RESUMO

Phaeodactylum tricornutum is a model microalgae that is widely used to study diatom physiology and ecology. Since the meiotic process and sexual cycle have never been observed directly, P. tricornutum has been considered to be an asexual species. However, phylogenetic analysis of the P. tricornutum genome has revealed a series of meiosis-specific gene homologues in this species. We identified two copies of differently transcribed SPO11 homologs that contain the conserved motifs of Winged-helix and Toprim domains. The homolog PtSPO11-3 interacts with TopoVIB in yeast two-hybrid analysis, whereas the homolog PtSPO11-2 could rescue the sporulation defect of a Spo11 yeast mutant strain. PtSPO11-2 was also found to be significantly up-regulated at low temperatures in P. tricornutum and its key catalytic residue was important to the homolog's function in sporulation. The results herein provide positive clue that meiosis and sexual reproduction could exist in this diatom.


Assuntos
Domínio Catalítico , Diatomáceas/genética , Endodesoxirribonucleases/metabolismo , Meiose , Microalgas/genética , Sequência Conservada , Diatomáceas/fisiologia , Endodesoxirribonucleases/química , Endodesoxirribonucleases/genética , Microalgas/fisiologia , Ligação Proteica , Multimerização Proteica
12.
Bioresour Technol ; 315: 123761, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32652437

RESUMO

Previous study has demonstrated that freshwater can be replaced with seawater for dilution of feed to algal production and wastewater treatment, but high harvest cost in suspended-growth systems is still a troublesome limitation for large-scale production. Therefore, a novel inclined algal biofilm photobioreactor (IABPBR) was constructed for algal bioproduct production and treatment of seawater-diluted anaerobically digested effluent (SA) in this study. Fluffy polyester was selected as the best carrier for the algal biofilm among ten discarded materials. With the help of phytohormones, the viability of SDEC-18 was clearly enhanced and an algal biomass productivity of 5.66 g/m2/d was achieved. The SDEC-18 biofilm provided removal capacities of 0.65, 0.25 and 3.31 g/m2/d for TN, TP and COD. Phytohormones clearly enhanced the lipid biosynthesis, with an extraordinary lipid productivity of 3.98 g/m2/d being achieved. Moreover, an automatic harvesting system was designed for the efficient harvesting process during large-scale production.


Assuntos
Microalgas , Fotobiorreatores , Biofilmes , Biomassa , Análise Custo-Benefício , Lipídeos , Reguladores de Crescimento de Planta , Água do Mar , Águas Residuárias
13.
Bioresour Technol ; 315: 123738, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32659423

RESUMO

Microalgae-based technology is an environmental-friendly and cost-effective method for biofuel production and pollutants removal. In this study, Scenedesmus obliquus (S. obliquus) was cultured with varying concentrations of ofloxacin (OFL) in BG11 medium. In the algae-antibiotics culture system, S. obliquus could effectively remove OFL with a concentration of 10 mg/L; however, the removal efficiency was restricted under higher doses (20-320 mg/L). Meanwhile, the lipid content significantly increased by 21.10-49.63%, which was caused by carbon being converted from carbohydrate to lipid. The greatest lipid productivity (7.53 mg/L/d) occurred at an OFL concentration of 10 mg/L, which was approximately 1.5-fold greater than the control. Moreover, S. obliquus cultured with OFL was able to improve the biodiesel quality due to an increase of saturated fatty acids and a decrease of unsaturated fatty acids. This study demonstrates that an algae-antibiotics system is a promising solution to simultaneously achieve antibiotics removal and biofuel production.


Assuntos
Microalgas , Scenedesmus , Biocombustíveis , Biomassa , Clorofíceas , Ofloxacino
14.
Bioresour Technol ; 315: 123801, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32673983

RESUMO

Pyrolysis of protein-rich biomass, such as microalgae, macroalgae, sewage sludge, energy crops, and some lignocellulosic biomass, produces bio-oil with high nitrogen (N) content, sometimes as high as 10 wt% or even higher. Major nitrogenous compounds in bio-oil include amines/amides, N-containing heterocycles, and nitriles. Such bio-oil cannot be used as fuel directly since the high N content will induce massive emission of nitrogen oxides during combustion. The present review comprehensively summarized the effects of biomass compositions (i.e., elemental, biochemical, and mineral compositions) and pyrolysis parameters (i.e., temperature, heating rate, atmosphere, bio-oil collection/fractionation methods, and catalysts) on the contents of N and the N-containing chemical components in bio-oil. The migration and transformation mechanisms of N during the pyrolysis of biomass were then discussed in detail. Finally, the research gaps were identified, followed by the proposals for future investigations to achieve the denitrogenation of bio-oil.


Assuntos
Microalgas , Pirólise , Biocombustíveis , Biomassa , Temperatura Alta , Nitrogênio
15.
Bioresour Technol ; 315: 123833, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32683286

RESUMO

In this study, the cross-talk between gama-aminobutyric acid (GABA) and calcium ion (Ca2+) signalling in the regulation of lipid production and cell growth in microalgae under fulvic acid and salinity stress (FA-salinity treatment) was investigated. GABA enhanced the lipid content and lipid productivity rate considerably, which were 1.27 and 1.29 times higher than those of the control, respectively. The levels of biosynthetic gene transcription, GSH, Ca2+ and cellular GABA were promoted by GABA addition, but decreased the ROS levels. Furthermore, the application of Ca2+ also increased lipid synthesis by regulating ROS and GABA signalling and lipogenesis-related genes. These results indicated that cytosolic GABA and Ca2+ levels exert crucial cross-talk in the modulation of cell growth and lipid accumulation induced by FA-salinity treatment. Collectively, this study demonstrated the beneficial effects caused by induction of the combination of chemical compounds on lipid production and provided new insights into lipid synthesis in microalgae.


Assuntos
Cálcio , Microalgas , Aminobutiratos , Benzopiranos , Lipídeos , Lipogênese , Salinidade , Estresse Salino
16.
Bioresour Technol ; 315: 123822, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32688254

RESUMO

Gravity settler was integrated into an algal membrane photobioreactor (MPBR) for in situ biomass concentration and harvesting of Graesiella emersonii. By continuous circulation of suspended biomass between MPBR and settler, biomass was sedimented in the settler and harvested. MPBR-Settler operations at different recirculation rates (0.15-2.4 L/d) and settler volumes (250-1000 mL) affected both suspended (0.4-3.4 g/L) and settled (16.1-31.1 g/L) biomass concentrations. Maximum biomass productivity of 0.26 ± 0.06 g/L/d was achieved in the 1000 mL settler operating at 0.6 L/d recirculation rate, which also yielded 9-131 times concentrated biomass (31.1 g/L) compared to the baseline MPBR (0.2-3.4 g/L). This novel design also facilitated MPBR operation at low solids retention times (6-8 d) without incurring large outflow of unfiltered effluent, while alleviating light limitation via biomass dilution. These results demonstrated that the MPBR-Settler system can provide an excellent way to mitigate light limitation, enhance biomass productivity, and simplify biomass harvesting.


Assuntos
Microalgas , Fotobiorreatores , Biomassa , Membranas Artificiais , Águas Residuárias
17.
Bioresour Technol ; 315: 123825, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32693344

RESUMO

Biogas/biomethane generation from microalgae biomass via anaerobic fermentation is increasingly gaining attention as CO2-neutral energy source. Intensive research has shown, however, that microalgae represent a rather challenging substrate for anaerobic digestion (AD) due to their high cell wall recalcitrance and unfavourable protein content. Previously, the utilization of nitrogen-limited (low-N) microalgal biomass for continuous AD-processes was demonstrated (as proof-of-concept) with remarkable biomethane productivity. The present study shows the efficient portability of the low-N cultivation/fermentation strategy on a robust, wastewater-borne microalga isolate that tolerates high temperature and light conditions and can perfectly cope with microbial contaminations. Continuous long-term anaerobic digestion was characterized by stable and efficient specific biogas and biomethane productivity (765 ± 20 and 478 ± 15 mLNg-1 volatile solids (VS) d-1, respectively), equivalent to volumetric methane productivity of 1912 mLN L-1d-1. The present work underlines the applicability of low-N-biomass of wastewater-borne, robust microalgae as mono-substrate for highly efficient continuous methane generation.


Assuntos
Chlamydomonas , Microalgas , Anaerobiose , Biocombustíveis , Biomassa , Metano , Águas Residuárias
18.
Bioresour Technol ; 315: 123857, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32707508

RESUMO

In the context of emerging biorefinery for microalgae, polyethyleneimine (PEI), has been tested in order to achieve separation of fat-soluble and water-soluble compounds from Haematococcus pluvialis. Several parameters were taken into account (ratio between sample and PEI, pH, and ionic strength) and 2 conditions (0.075% PEI pH 7.4, and 0.100% PEI pH8.5) were studied for up-scalability, with a recovery of flocculated compounds (lipids and pigments), and a complete characterization of both phases. Using 0.075% PEI, pH7.4, 100% sugars and 89.8% proteins were retained in the supernatant, but some trace of beta-carotene were also detected. For 0.100% PEI, pH 8.5, a loss in proteins content was highlighted (61.2% proteins retained), but no residual lipids or pigments were detected. PEI could therefore be considered as an efficient method to fractionate fat-soluble and water-soluble compounds from microalgae.


Assuntos
Microalgas , Fracionamento Químico , Clorofíceas , Floculação , Polietilenoimina
19.
Bioresour Technol ; 315: 123880, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32717519

RESUMO

This study aimed to investigate the influence of different intensities (15, 30 and 60 mT) and exposure times (1 h d-1, 24 h d-1) of magnetic fields (MF) on the stimulation of lipid synthesis by the microalga Chlorella homosphaera. The growth and biochemical characterization of protein, carbohydrate and lipid content were determined. Biomass concentration increased by 20.6% (30 mT, 1 h d-1) and 12.4% (60 mT, 1 h d-1) in the presence of MF. However, biomass decreased by 33.0% (15 mT, 1 h d-1) in relation to control cultivation (CC). The stress caused by the MF application stimulated lipid synthesis and biomass production. In all evaluated conditions, MF application showed a positive effect on lipid production; the application of 60 mT or 30 mT for 1 h d-1 increased lipid productivity by 108.4% and 135.1%, respectively. MF application with ferrite magnets was thus efficient to stimulate lipid synthesis.


Assuntos
Chlorella , Microalgas , Biocombustíveis , Biomassa , Clorofíceas , Lipídeos , Campos Magnéticos
20.
Bioresour Technol ; 315: 123842, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32717521

RESUMO

The metabolism of heterotrophic and mixotrophic cultivation modes of Chlorella vulgaris, a potential source of biofuel and CO2 mitigation, was studied in immobilized cultures. The gas concentration (O2 and CO2) was measured thanks to an original device manufactured using 3D printing. The biomass was monitored by 3D imaging and image processing. Net O2 and CO2 sources were obtained by a balance equation considering a calibrated leakage and the dissolved gas. Combined experimental and theoretical gas yields (mass of gas per mass of biomass), the photosynthesis proportion of mixotrophic colony was determined. Its increase with light intensity is not linear. Therefore, the highest light intensity (104µmol∙m-2∙s-1) revealed the limit of photosynthesis potential in the growth of mixotrophic colony. In the presence of light, the colony adopts a cylindrical shape instead of a spherical cap. This study proposed mechanisms of synergy inside the colony for heterotrophic and mixotrophic modes.


Assuntos
Chlorella vulgaris , Microalgas , Biomassa , Processos Heterotróficos , Fotossíntese
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