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1.
Biotechnol Adv ; : 107444, 2019 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-31476422

RESUMO

Photosynthetic biogas upgrading using microalgae provides a promising alternative to commercial upgrading processes as it allows for carbon capture and re-use, improving the sustainability of the process in a circular economy system. A two-step absorption column-photobioreactor system employing alkaline carbonate solution and flat plate photobioreactors is proposed. Together with process optimisation, the choice of microalgae species is vital to ensure continuous performance with optimal efficiency. In this paper, in addition to critically assessing the system design and operation conditions for optimisation, five criteria are selected for choosing optimal microalgae species for biogas upgrading. These include: ability for mixotrophic growth; high pH tolerance; external carbonic anhydrase activity; high CO2 tolerance; and ease of harvesting. Based on such criteria, five common microalgae species were identified as potential candidates. Of these, Spirulina platensis is deemed the most favourable species. An industrial perspective of the technology further reveals the significant challenges for successful commercial application of microalgal upgrading of biogas, including: a significant land footprint; need for decreasing microalgae solution recirculation rate; and selecting preferable microalgae utilisation pathway.

2.
Sci Total Environ ; 697: 134097, 2019 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-31484090

RESUMO

Heavy metals inevitably cause invisible or visible damage to plants, leading to significant economic losses. Therefore, it is necessary to develop a method for timely monitoring the damage of plants under the stress of heavy metals. Here, vitronectin-like proteins (VN) on the surface of plant cells is as an important biomarker for monitoring damage of plants under the stress of heavy metals. A living plant cell-based biosensor is constructed to monitor invisible damage of plant cells induced by cadmium [Cd(II)] or lead [Pb(II)]. To fabricate this sensor, l-cysteine was first modified on the glassy carbon electrode followed by the modification of anti-IgG-Au antibody. Then, the living plant cells, incubated with the anti-VN, were modified onto the electrode. The sensor worked by determining the change in electrochemical impedance. Cd(II) and Pb(II) was detected in the linear dynamic range of 45-210 and 120-360 µmol·L-1, respectively. And the detection limit of Cd(II) and Pb(II) of this biosensor was 18.5 nmol·L-1 [with confidence interval (95%) 18.4-18.6 nmol·L-1] and 25.6 nmol·L-1 [with confidence interval (95%) 25.4-25.8 nmol·L-1], respectively. In both Arabidopsis and soybean, when the content of VN increased by about 20 times under the stress of Cd(II) or Pb(II), which means when the electron-transfer resistance increased by 35%, chlorophyll content showed significant decrease about 17%. Therefore, by establishing a quantitative relationship among the content of biomarker, the electron-transfer resistance and chlorophyll content in plant cells, the invisible damage of plants under the stress of heavy metals was detected. These results can provide a reference method for early-onset warning systems for heavy metal pollution in the environment.

3.
Bioresour Technol ; 293: 122056, 2019 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-31514117

RESUMO

Aiming at optimizing the adsorption process of Chlorella vulgaris and cationic starch, the adsorption thermodynamic characteristics were evaluated. Different from inorganic calcium salt adsorbent, the adsorption nature of organic polymer cationic starch is exothermic (ΔH°â€¯< 0) and spontaneous (ΔG°â€¯< 0). Besides, the adsorption capacity and rate can be well described by Langmiur isotherm and pseudo second kinetic models. As results of exothermic nature and great driving force of lower temperature, the adsorption capacity and rate declined with the rising temperature. The maximal values of them were obtained at 278.15 K, which were 9148.14 mg microalgae (g cationic starch)-1 and 8.74 × 10-6 mg g-1 min-1. Additionally, with insufficient adsorbent, the highest adsorption efficiency (96.37%) was achieved at 278.15 K for stirring 150 min. For 288.15, 298.15, 308.15 and 318.15 K, the adsorption efficiency decreased to 93.77%, 86.75%, 83.32% and 81.57% and the time consumed were at least 40 min longer.

4.
Bioresour Technol ; 292: 121947, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31466821

RESUMO

Photobioreactor (PBR) is the most critical equipment for microalgal photosynthetic fixation of CO2. It provides suitable environmental conditions, such as CO2, light and nutrients, for microalgal growth. As the major carbon source for microalgae, CO2 gas is pumped into PBR with the formation of bubbles and formed gas-liquid flow. The gas-liquid flow affects CO2 and nutrients transmission as well as microalgae cells distribution in PBR, thereby affecting the biochemical reaction of microalgae. While the migration and transport of biochemical reaction products affect the two-phase flow, phase distribution and flow resistance in the PBR in return, thus affecting the transport of light and nutrients. Therefore, microalgal photosynthetic rate is determined synthetically by two-phase flow and the transport of CO2, light and nutrients in PBR. Deep understanding of gas-liquid two-phase flow, energy and mass transfer coupling with microalgal growth in PBR is the cornerstone for the design of an efficient microalgae PBR.

5.
Bioresour Technol ; 289: 121727, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31279318

RESUMO

In this present study, microalgal phycobiliproteins were isolated and purified via potential biphasic processing technique for pharmaceutical as well as food applications. The algal pre-treatment techniques were studied to enhance the yield of microalgal phycobiliproteins from the biomass. The proposed methods were optimised to obtain the best recovery yield of phycobiliproteins that can be isolated from the biomass. The phycobiliproteins were further purified using liquid biphasic system. The results showed that microalgal phycobiliproteins of high purity and yield was achieved using sonication treatment (20% power, 50% duty cycle and 7 min of irradiation time) with the biphasic system, where the purification fold of 6.17 and recovery yield of 94.89% was achieved. This work will provide insights towards the effective downstream processing of biomolecules from microalgae.

6.
Bioresour Technol ; 289: 121709, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31276992

RESUMO

Biogas production from microalgae biomass without pretreatment and with hydrothermal pretreatment involve the energy with different quality and quantity, which makes it complex to evaluate thermodynamic performance. In this paper, exergy analyses were conducted in biogas production from microalgae biomass without pretreatment, with hydrothermal pretreatment, and with solar-driven hydrothermal pretreatment. The results showed that the materials and energy flow affected exergy efficiency in biogas production from microalgae biomass. The biogas production from microalgae biomass with solar-driven hydrothermal pretreatment achieved the highest exergy efficiency (40.85%), compared with that without pretreatment (26.2%) and with hydrothermal pretreatment (35.98%). In addition, the maximum exergy loss was caused by biogas residue, which accounted for 60.58%, 38.54%, and 35.13% of overall exergy input in biogas production from microalgae biomass without pretreatment, with hydrothermal pretreatment, and with solar-driven hydrothermal pretreatment, respectively. Exergy analyses provide important theoretical guidance to improve the performance of biogas production from microalgae biomass.


Assuntos
Biocombustíveis , Biomassa , Microalgas/metabolismo , Anaerobiose , Termodinâmica
7.
Bioresour Technol ; 288: 121560, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31170688

RESUMO

An advanced electrodialysis fermentation system was set up to remove ammonium during hydrogen fermentation. When the voltage was increased from 0 to 6 V, the average ammonium removal rate was improved from 8.7 to 31.1 mg/L/h at an initial ammonium concentration of 3000 mg/L. A model based on the Nernst-Plank equation and porous media properties of ion exchange membranes was successfully implemented to predict the ammonium removal performance. When such a system was fed with synthetic wastewater at an ammonium concentration of 3000 mg/L for hydrogen fermentation, a significant increase in specific hydrogen yield was observed in the experiment group at 4 V. Specific hydrogen yield was 225.0 mL/g glucose, this value is 47.9% higher than the control. Moreover, ammonium concentration in experiment group was reduced to 701.6 mg/L at 72 h when voltage was set at 4 V, which is 63.7% lower than that in 0 V experiment group.

8.
Bioresour Technol ; 289: 121650, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31228746

RESUMO

Hydrothermal pretreatment is an efficient process for improving the productivity of biofuels from wet microalgae biomass. The rheological behavior of microalgae slurry is a significant parameter affecting the performance of hydrothermal pretreatment reactors. Herein, the dynamic rheological behavior of microalgae slurry during hydrothermal pretreatment was investigated for the first time. The results revealed that the insoluble organics released from microalgae cells was the main factor affecting the rheological behavior of microalgae slurry. The denaturation and hydrolysis of starch and protein in liquid phase at different temperature regions caused the increasing and decreasing of viscosity of the microalgae slurry, respectively. The rheokinetics equations were established based on four-parameter cross-linking rheokinetics equation to describe the variation of viscosity with reaction time in different temperature. The variation of the rheokinetics model parameters with temperature revealed that the temperature has an obviously positive influence on the hydrothermal pretreatment process of the microalgae slurry.

9.
Proc Natl Acad Sci U S A ; 116(28): 14349-14357, 2019 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-31239335

RESUMO

Endocytosis is essential to all eukaryotes, but how cargoes are selected for internalization remains poorly characterized. Extracellular cargoes are thought to be selected by transmembrane receptors that bind intracellular adaptors proteins to initiate endocytosis. Here, we report a mechanism for clathrin-mediated endocytosis (CME) of extracellular lanthanum [La(III)] cargoes, which requires extracellular arabinogalactan proteins (AGPs) that are anchored on the outer face of the plasma membrane. AGPs were colocalized with La(III) on the cell surface and in La(III)-induced endocytic vesicles in Arabidopsis leaf cells. Superresolution imaging showed that La(III) triggered AGP movement across the plasma membrane. AGPs were then colocalized and physically associated with the µ subunit of the intracellular adaptor protein 2 (AP2) complexes. The AGP-AP2 interaction was independent of CME, whereas AGP's internalization required CME and AP2. Moreover, we show that AGP-dependent endocytosis in the presence of La(III) also occurred in human cells. These findings indicate that extracellular AGPs act as conserved CME cargo receptors, thus challenging the current paradigm about endocytosis of extracellular cargoes.

10.
Bioresour Technol ; 278: 272-278, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30708330

RESUMO

Due to the small size, similar density to water, cells inoculating onto the solid carrier is a major challenge for microalgae biofilm cultivation. To reduce biofilm inoculation time, A. falcatus with long stripe were chosen as the bond linking with the main microalgae cells forming microalgae-microalgae co-flocculation by bridging and twining. The optimal matching species were S. obliquus and A. falcatus with the volume ratio of 4-1. By changing the zeta-potential of the microalgae-microalgae co-flocculation to positive and negative through pH regulating, the inoculation time was significantly shorted from 4 h to 1.5 min due to the charge neutralization. Fortunately, the added A. falcatus and pH regulation has no negative effects on biofilm growth. Inversely, the porous microstructure of microalgae-microalgae co-flocculation improve the transfer efficiency of nutrients, resulting a 90.15% increase on biomass productivity (229.15 g m-2) comparing to pure microalgae species.


Assuntos
Biofilmes , Microalgas/fisiologia , Biomassa , Floculação , Fatores de Tempo
11.
Bioresour Technol ; 276: 133-139, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30623867

RESUMO

To improve the carbon to nitrogen (C/N) ratio of harvested microalgae biomass for better producing biogas by fermentation, biodegradable cationic starch with high C/N ratio were synthesized to harvest Chlorella vulgaris. The impact of pH was also studied as the zeta potential of both microalgae and cationic starch would change with pH. Results indicated the cationic starch can harvest above 99% of the microalgae and the C/N ratio can rise from 7.50 to 7.90. The zeta potential of microalgae always kept negative and presented a trend of descending firstly and then upgrade. The maximum microalgae biomass flocculation capacity of 1 g cationic starch was 8.62 g with the help of self-flocculation at pH 3. The concentration of flocs formed at pH 11 was 25.74 g L-1 and the diameter was 0.553 mm which was much larger than the flocs formed at pH 3 (0.208 mm).


Assuntos
Carbono/metabolismo , Chlorella vulgaris/metabolismo , Microalgas/metabolismo , Nitrogênio/metabolismo , Amido/metabolismo , Biomassa , Cátions/química , Floculação , Concentração de Íons de Hidrogênio
12.
iScience ; 10: 158-170, 2018 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-30528903

RESUMO

Interspecies electron transfer is a fundamental factor determining the efficiency of anaerobic digestion (AD), which involves syntrophy between fermentative bacteria and methanogens. Direct interspecies electron transfer (DIET) induced by conductive materials can optimize this process offering a significant improvement over indirect electron transfer. Herein, conductive graphene was applied in the AD of protein-derived glycine to establish DIET. The electron-producing reaction via DIET is thermodynamically more favorable and exhibits a more negative Gibbs free energy value (-60.0 kJ/mol) than indirect hydrogen transfer (-33.4 kJ/mol). The Gompertz model indicated that the kinetic parameters exhibited linear correlations with graphene addition from 0.25 to 1.0 g/L, leading to the highest increase in peak biomethane production rate of 28%. Sedimentibacter (7.8% in abundance) and archaea Methanobacterium (71.1%) and Methanosarcina (11.3%) might be responsible for DIET. This research can open up DIET to a range of protein-rich substrates, such as algae.

13.
Biochem Biophys Res Commun ; 503(4): 2504-2509, 2018 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-30208518

RESUMO

The upconversion luminescence (UCL) marker based on upconversion nanoparticles (UCNPs) shows unique advantages over traditional fluorescence markers, such as enhanced tissue penetration, better photostability, and less autofluorescence. Herein, we constructed a new UCL gene-delivery nonviral vector via layer-by-layer self-assembly of poly(ethylene imine) (PEI) with UCNPs. To reduce the cytotoxicity of PEI, citric acid (CA) was introduced for aqueous modification, and PEI assembly was introduced on the UCNP surface. Our data show that the nonviral vector for UCL gene-delivery demonstrates excellent photostability, low toxicity, and good stability under physiological or serum conditions and can strongly bind to DNA. Moreover, this UCL PEI-based vector could serve as a promising fluorescent gene-delivery carrier for theranostic applications.

14.
Bioresour Technol ; 269: 292-299, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30193213

RESUMO

Flat-plate photobioreactor (PBR) with perforated inverted arc trough (PIAT) internals was proposed to promote CO2 bio-fixation by microalgae. The PIAT internals can enhance CO2 transfer from gas to culture medium by prolonging CO2 gas-liquid contact time and generate periodic aeration in the suspension upper side the PIAT providing suspension mixing. Experimental results showed gas-liquid contact time was prolonged from 0.448 s to 256 s and the CO2 partial pressure inside the PIAT internals was about 15.5 kPa during microalgae cultivation. Consequently, the dissolved CO2 concentration in the microalgae suspension of the proposed PBR was increased by 26.0% compared to that in the PBR without PIAT internals when 15% CO2 (v/v) was aerated at a rate of 15 mL min-1. The elevated CO2 transfer contributed to a 20.9% increment in biomass concentration (3.35 g L-1) and a 26.2% increment in CO2 fixation rate (36.6 mg L-1 h-1).


Assuntos
Dióxido de Carbono/metabolismo , Microalgas , Fotobiorreatores , Biomassa , Meios de Cultura
15.
Bioresour Technol ; 270: 38-45, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30212772

RESUMO

To optimize the designing of microalgae slurry pumping system and enhance the efficiency of microalgae products production, the flow characteristics of microalgae slurries (Chlorella pyrenoidosa) in tube flow were for the first time investigated combining experiments and numerical simulation. The drag reduction behavior of microalgae slurry in the fully developed laminar flow regime was studied. In addition, the transition Reynolds number of microalgae slurries from laminar flow to turbulent flow was about 1000-1300, which was similar to the expression of two-phase flow. To provide a further understanding of flow feature of microalgae slurries in tube, a two-phase mixture model was proposed by considering the heterogeneity of concentration due to the shear-induced microalgae cells migration behavior. Simulation results revealed that the heterogeneous distribution of concentration was affected by average velocity and volume fraction of microalgae slurries, significantly affecting the flow resistance and flow stability of microalgae slurry in the tube flow.

16.
Bioresour Technol ; 270: 80-87, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30212777

RESUMO

In order to solve the technical bottleneck that the biomass yield and lipid accumulation cannot be increased simultaneously during microalgae growth, a heterotrophic-assisted photoautotrophic biofilm (HAPB) growth mode of Chlorella vulgaris was constructed. The light penetration capability of the microalgae biofilm formed through heterotrophic-assisted photoautotrophic growth was 64% stronger than that formed by photoautotrophic growth. Due to the different demands of autotrophic and heterotrophic growth of microalgae, the nutrient environment and growth conditions were optimized to fully utilize the advantages and potentials of the HAPB culture model. An optimized molar ratio of total inorganic carbon (CO2) to total organic carbon (glucose) (20:1) and a molar ratio of total carbon to total nitrogen (72:1) were obtained. The maximum specific growth rate of Chlorella vulgaris increased by 78% compared to that before optimization. Meanwhile, the lipid content and yield increased by 120% and 147%, respectively, up to 47.53% and 41.95 g m-2.

17.
Bioresour Technol ; 266: 306-314, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29982052

RESUMO

Biofuel production from microalgae biomass via fermentation is promising as a renewable technology. Hydrothermal hydrolysis pretreatment of microalgae slurry prior to fermentation is an efficient method to enhance the biogas production. Herein, we report, for the first time, the hydrothermal hydrolysis pretreatment of microalgae slurries in a continuous reactor under subcritical conditions (temperature <200 °C, pressure ∼2 MPa). The results show that the yield of carbohydrates from microalgae slurries first increased and then decreased with increasing average outlet temperature, which reached a maximum value at 160 °C for 10 min. This phenomenon was caused by the combined effects of the release of organics and biochemical reactions. Notably, the radial temperature distribution of microalgae slurries, influenced by the mass fraction and the flow rate during the heating process, had effects on the yield of organics (carbohydrates, proteins) in aqueous solution. This study provides useful information for the operating conditions in large-scale applications.


Assuntos
Biocombustíveis , Microalgas , Biomassa , Hidrólise , Temperatura Ambiente
18.
Bioresour Technol ; 263: 437-443, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29772505

RESUMO

A three-chamber electrodialysis bioreactor comprising fermentation, cathode and anode chambers was proposed to remove in situ volatile fatty acids during hydrogen fermentation. The electrodialysis voltage of 4 V resulted in a volumetric hydrogen productivity of 1878.0 mL/L from the fermentation chamber, which is 55.4% higher than that (1208.5 mL/L) of the control group without voltage applied. Gas production was not observed in the cathode and anode chambers throughout fermentation. By applying different voltages (0-6 V), the hydrogen content accumulated to 54.6%-84.7%, and it exhibited increases of 7.1%-66.4% compared with that of the control. Meanwhile, the maximum concentrations of acetate and butyrate in the fermentation chamber decreased to 10.3 and 13.1 mmol/L at a voltage of 4 V, respectively, which are 68.0% and 62.4% lower than that for the control.


Assuntos
Ácidos Graxos Voláteis/metabolismo , Fermentação , Hidrogênio/análise , Reatores Biológicos , Ácido Butírico , Concentração de Íons de Hidrogênio
19.
Bioresour Technol ; 261: 36-43, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29653332

RESUMO

Attachment of cells to substrate surface is the premise for biofilm formation. To shelter microalgae cells from fluid shear stress and offer larger areas for microalgae attachment, the inerratic microgrooves, which can act as anchor points that offer larger areas for microalgae attachment and induce vortex to protect cells from hydraulic shear stress, were designed and fabricated into substrate surface. The results indicated that the shear stress on the surface with V-grooves was weaker than that on the surface with U-grooves, and 45° V-grooves with the width of 200 µm were benefit for cells attachment. The initial attachment time was shortened to 50 min under the hydraulic shear stress of 0.02 Pa compared to that of 135 min on the surface without microgrooves. Subsequently, the biofilm biomass concentration on the surface with 45° V-grooves increased by 14.29% to 165.84 g m-2 compared with that on flat substrates.


Assuntos
Biofilmes , Microalgas , Biomassa , Estresse Mecânico , Propriedades de Superfície
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