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1.
Mater Sci Eng C Mater Biol Appl ; 128: 112354, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34474902

RESUMO

In this paper, silk fibroin (SF) porous microcarriers containing strontium were constructed as injectable bone tissue engineering vehicles. The effects of SF concentration and strontium content on micromorphology, element distribution, strontium ion release and cellular behavior of the constructed microcarriers were investigated. The microcarriers with an open interconnected pore can be fabricated by controlling the concentration of SF. The strontium functionalized SF microcarriers showed the sustained release of strontium ion and allowed bone mesenchymal stem cells (BMSCs) to attach, proliferate and secrete extracellular matrix. Furthermore, the strontium functionalized SF microcarriers improved the osteogenic capability of BMSCs in vitro compared with those microcarriers without sustained release of strontium ion. This study presents a valuable approach to fabricate polymeric microcarriers with the capability of sustained release of strontium ion that show potential in bone tissue engineering applications.


Assuntos
Fibroínas , Diferenciação Celular , Osteogênese , Porosidade , Estrôncio , Engenharia Tecidual , Tecidos Suporte
2.
Environ Sci Pollut Res Int ; 27(23): 29239-29247, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32440871

RESUMO

Harmful algal blooms (HABs) are a growing problem worldwide, damaging human and ecosystem health. In this study, a novel buoyant-bead flotation (BBF) method using chitosan-coated fly ash cenospheres (CFACs) was developed to remove HABs in freshwater. To achieve a high removal efficiency of harmful algae (Chlorella vulgaris, Scenedesmus quadricauda, and Microcystis aeruginosa), this study investigated the effects of chitosan/fly ash ratios in CFAC composite, CFAC concentration, flotation time, and pH values on the microalgae removal. The optimized ratio of CFACs is 0.1:12, and the optimized CFAC concentration is 0.3-0.7 g L-1. However, the lower or higher ratios (0.1:4, 0.1:8, 0.1:16) result in microalgae reaching a zero-point charge too late or early, which failed to effectively remove HABs with an appropriate coal fly ash dosage. An optimized removal efficiency of 98.50% for Microcystis aeruginosa was reached at pH of 6.0. The optimized efficiency of Scenedesmus quadricauda and Chlorella vulgaris was 99.37% and 91.63%, respectively, at pH of 8.0. At neutral pH conditions, the surface charge of microalgae cells and CFACs are different, promoting aggregate formation. When CFACs were used to remove microalgae, aggregate size significantly influenced removal efficiency. Meanwhile, at the optimized pH and concentration, the removal efficiency of all three algal species exceeded 90.00% in 5 min. The study highlights an efficient and inexpensive method for removing HABs and obtains the optimized operational conditions.


Assuntos
Quitosana , Chlorella vulgaris , Cinza de Carvão , Ecossistema , Floculação , Água Doce , Proliferação Nociva de Algas
3.
Water Sci Technol ; 80(3): 426-436, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31596254

RESUMO

Thermal pre-flocculation to enable dispersed air flotation is an economical and ecofriendly technology for harvesting microalgae from water. However, the underlying mechanism and optimal conditions for this method remain unclear. In this study, Chlorella vulgaris (C. vulgaris) and Scenedesmus obliquus (S. obliquus) were harvested using a thermal flotation process. The surface structure and characteristics (morphology, electricity, and hydrophobicity) of the microalgae were analyzed using FT-IR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy), zeta potential, and a hydrophobic test. Further, response surface methodology (RSM) was used to optimize the flotation process. The hydrophobicity of S. obliquus exceeded that of C. vulgaris; as such, under the thermal pre-flocculation, S. obliquus (88.16%) was harvested more efficiently than C. vulgaris (47.16%). Thermal pre-flocculation denatured the lipids, carbohydrate, and proteins of microalgal cell surfaces. This resulted in a decrease in the electrostatic repulsion between the cells and air bubbles. The highest harvesting efficiency was 91.96% at 70 °C, 1,412 rpm, and 13.36 min. The results of this study demonstrate the potential for economic and ecofriendly harvesting of microalgae for biofuels and other bioproducts industries.


Assuntos
Chlorella vulgaris , Microalgas , Biocombustíveis , Biomassa , Floculação , Espectroscopia de Infravermelho com Transformada de Fourier
4.
Appl Microbiol Biotechnol ; 103(19): 8255-8265, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31396677

RESUMO

Coupling algal cultivation with wastewater treatment due to their potentials to alleviate energy crisis and reduce environmental burden has attracted the increased attention in recent years. However, these microalgal-based processes are challenging since daily and seasonal temperature fluctuation may affect microalgal growth in wastewater, and the effects of the temperature regimes on microalgal biomass production and wastewater nutrient removal remain unclear. In this study, Chlorella vulgaris was continuously cultured for 15 days in municipal wastewater to investigate the effects on the algal biomass and wastewater nutrient removal in three temperature regimes: (1) low temperature (4 °C), (2) high temperature (35 °C), and (3) alternating high-low temperature (35 °C in the day: 4 °C at night). Compared with the other two temperature regimes, the high-low temperature conditions generated the most biomass (1.62 g L-1), the highest biomass production rate (99.21 mg L-1 day-1), and most efficient removal of COD, TN, NH3-N, and TP (83.0%, 96.5%, 97.8%, and 99.2%, respectively). In addition, the polysaccharides, proteins, lipid content, and fatty acid methyl ester composition analysis indicates that in alternating high-low temperature condition, biomass production increased the potential for biofuel production, and there was the highest lipid content (26.4% of total dry biomass). The results showed that the nutrients except COD were all efficiently removed in these temperature conditions, and the alternating high-low temperature condition showed great potential to generate algal biomass and alleviate the wastewater nutrients. This study provides some valuable information for large-scale algal cultivation in wastewater and microalgal-based wastewater treatments.


Assuntos
Chlorella vulgaris/crescimento & desenvolvimento , Chlorella vulgaris/efeitos da radiação , Compostos Orgânicos/metabolismo , Temperatura , Águas Residuárias/microbiologia , Poluentes Químicos da Água/metabolismo , Purificação da Água/métodos , Biomassa , Lipídeos/análise , Polissacarídeos/análise , Proteínas/análise , Águas Residuárias/química
5.
Bioprocess Biosyst Eng ; 42(3): 391-400, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30460400

RESUMO

Harvesting technology has a significant influence on the microalgal biomass industry. This study develops a buoy-bead flotation method and analyzes the factors impacting flotation. Experimental results show that adding sodium borosilicate as an alternative microsphere material can result in 58.5% harvesting efficiency, a 25.65% increase over the foam flotation average. The Plackett-Burman design experimental results reveal that pH conditions, microsphere diameter, and the speed of agitation are the three most important factors affecting harvesting efficiency. The interaction between these three factors was all found to be significant, which indicates that the harvesting efficiency was affected by a combination of multiple factors. Analyses of the Extended Derjaguin-Landau-Vewey-Overbeek (XDLVO) theory show that the Van der Waals interactions are the key factor in the attachment of algae and microspheres. A harvesting efficiency of 89.9% can be achieved at pH 10, with 56 µm dimeter microspheres and an agitation speed of 114 rpm.


Assuntos
Biomassa , Chlorella vulgaris/crescimento & desenvolvimento , Microalgas/crescimento & desenvolvimento , Microesferas , Floculação
6.
Bioresour Technol ; 267: 341-346, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30029180

RESUMO

To improve microalgae harvesting efficiency and to reduce the addition of chemicals in the buoy-bead flotation process, a novel buoy-bead flotation approach has been developed for harvesting Chlorella vulgaris, using surface-layered polymeric microspheres (SLPMs). Next, the detachment of microalgae cell-SLPM aggregates and the reusability of SLPMs were investigated. The experimental results showed that a maximum harvesting efficiency of 98.43% was achieved at a SLPM dosage of 0.7 g/L and a pH of 9, and harvesting efficiency quickly decreased with increasing ionic strength. A detachment efficiency of 78.46% and a concentration factor of 19.56 were achieved at an ionic strength of 700 mM and a mixing speed of 3000 rpm without changing the pH. Reused SLPMs can still reach an efficiency of 72.13% after five cycles. The presented results show that this method can potentially be applied for large-scale microalgae harvesting.


Assuntos
Chlorella vulgaris , Microesferas , Biomassa , Chlorella , Floculação , Microalgas
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