Separation Of Microalgae Research Articles

Design and Application of Silica Micro-Clusters for Microalgae Separation

Eutrophication has attracted social’s attention as it is a worldwide problem in freshwater aquatic ecosystem. Therefore, cultivation of microalgae in nutrient-rich medium can serve as wastewater treatment as they remove the pollutants from aquatic environment and the microalgal biomass can produce biofuels or other valuable bioproducts. Although microalgae harvesting by gravity sedimentation method is less expensive but it promotes slow sedimentation rate and increases the possibility of biomass deteriorates during harvesting process. In this research, the silica micro-clusters (SMCs) was being synthesized and surface functionalized by positively charged chitosan to improve the attachment with microalgal cells in order to promote rapid microalgae removal through sedimentation. The cell removal efficiency of Chlorella sp. can reach up to 99.41 ± 0.64 % by using 1 g/L of surface functionalized SMCs (SF-Si). Moreover, it also tended to promote high rate of cell sedimentation at 22.71 ± 3.02 cm/h which was about 162 times faster than self-sedimentation. This method of silica-aided-sedimentation (SAS) had proven effective to harvest the multi-species microalgal cells which collected from Tualang lake, Perak, and achieved cell separation efficiency up to 100% by 80 mg/L of SF-Si.

Identification of microalgae from waste stabilization ponds and evaluation of electroflotation by alternate current for simultaneous biomass separation and cell disruption

ABSTRACT This work aimed to investigate algal diversity at the genus level in stabilization pond systems treating domestic wastewater and to evaluate the feasibility of an electroflotation by alternate current (EFAC) system for simultaneous microalgae separation and cell disruption. Evaluation of algal diversity showed that the genera Euglena and Chlorella were present in relatively high frequencies in five of the six effluents analyzed. The use of EFAC on an effluent that presented bloom of Chlorella achieved turbidity and chlorophyll-a removal efficiencies higher than 70 and 90%, respectively, after 70 minutes of operation. Total lipid yield for the Chlorella-rich biomass was 21.4±2.02%. Such high biomass lipid content demonstrates the potential for obtaining lipid-based biofuels from wastes. The current paper describes the first attempt, with promising results, at using electroflotation by alternate current for low cost, simultaneous microalgae harvesting and disruption.

Sheathless separation of microalgae from bacteria using a simple straight channel based on viscoelastic microfluidics

Microalgae cells have been recognized as a promising sustainable resource to meet worldwide growing demands for renewable energy, food, livestock feed, water, cosmetics, pharmaceuticals, and materials. In order to ensure high-efficiency and high-quality production of biomass, biofuel, or bio-based products, purification procedures prior to the storage and cultivation of the microalgae from contaminated bacteria are of great importance. The present work proposed and developed a simple, sheathless, and efficient method to separate microalgae Chlorella from bacteria Bacillus Subtilis in a straight channel using the viscoelasticity of the medium. Microalgae and bacteria migrate to different lateral positions closer to the channel centre and channel walls respectively. Fluorescent microparticles with 1 μm and 5 μm diameters were first used to mimic the behaviours of bacteria and microalgae to optimize the separating conditions. Subsequently, size-based separation in Newtonian fluid and in viscoelastic fluid in straight channels with different aspect ratios was compared and demonstrated. Under the optimal condition, the removal ratio for 1 μm microparticles and separation efficiency for 5 μm particles can reach up to 98.28% and 93.85% respectively. For bacteria and microalgae cells separation, the removal ratio for bacteria and separation efficiency for microalgae cells is 92.69% and 100% respectively. This work demonstrated the continuous and sheathless separation of microalgae from bacteria for the first time by viscoelastic microfluidics. This technique can also be applied as an efficient and user-friendly method to separate mammalian cells or other kinds of cells.

Effect of Physical, Chemical and Biological Mechanisms on the Solid-Liquid Separation of Microalgae

Effect of Physical, Chemical and Biological Mechanisms on the Solid-Liquid Separation of Microalgae

The Separation of Microalgae Using Dean Flow in a Spiral Microfluidic Device

A cell-in-droplet encapsulation using Dean flow in a spiral microfluidic device was applied to separate microalgae. In recent years, researchers have been interested in separating micro particles using microfluidic chips because of its great advantages in relation to various applications such as in biotechnology, medical examination, and cell studies. The main disadvantage of these microfluidic chips is particle clogging that decreases the separation yield, which then creates difficulties during the investigation of the particles. The microfluidic chip that is introduced in this work is a combination of two distinct designs—a spiral microchannel design to separate microalgae of various sizes, and a microdroplet generation design for cell encapsulation. The yield of the separation is enhanced through the concept of dominant forces (Dean drag force and lift force) in a spiral microchannel design, together with a design of the microdroplet generation that narrows the volume to facilitate cell observation. We report the development of cells, particle separation, and microdroplet generation. Using the spiral microchannel design can solve the clogging problem by distributing the microalgae evenly for the microdroplet generation section. A spiral microfluidics design was used as a separator for the different sized particles and a microdroplets generation design was used to encapsulate the separated particles. As for the design for the microdroplets generation section, a 3-way microchannel was designed. In this research, two kinds of microalgae have been used: the smaller one is chlorella vulgaris and the bigger one is cosmarium. Because of all of these benefits, this device might be an alternative for cell applications using droplet-based platforms. With a different channel height design, the separation efficiency for Chlorella vulgaris is about 75–80% and for Cosmarium is about 60–72%.

Harvesting microalgae using ionic polyelectrolytes in an aqueous-organic two-phase system: Screening of separation parameters using model algal particles

Abstract Separation and recovery of microalgae from the aqueous medium that they reside in is difficult as a result of the nature of the algal cells, i.e., small cell size, density close to water, low concentration, and ability to stay suspended in water due to surface potential. In this study, an easy technique that can separate microalgae from aqueous phase to a water-immiscible organic phase utilizing the natural zeta potential of microalgae is reported. The technique involves the addition of the positively charged electrolyte, Mono/Poly-(diallyl dimethyl ammonium chloride, DADMAC), which then interacts with the negatively charged biomass. The particle-bound electrolyte results in the formation of a hydrophobic ensemble which in turn migrates the particles from the aqueous phase to hydrophobic organic solvent phase. Approximately 80–85% of cellulose beads (model particles) and 80–82% of algae cells were displaced into hexane phase. Studies also indicated that the technique could be used to extract lipids without subjecting algal cells to disruption. The results pave the way for developing a low-cost method to dewater and separate whole algal cells by utilizing the inherent charges they carry. We anticipate the results being a starting point for the development of new separation technology targeting bioprocessing industry.

Bare Iron Oxide Nanoparticles for Magnetic Harvesting of Microalgae: From Interaction Behavior to Process Realization.

Microalgae continue to gain in importance as a bioresource, while their harvesting remains a major challenge at the moment. This study presents findings on microalgae separation using low-cost, easy-to-process bare iron oxide nanoparticles with the additional contribution of the upscaling demonstration of this simple, adhesion-based process. The high affinity of the cell wall for the inorganic surface enables harvesting efficiencies greater than 95% for Scenedesmus ovalternus and Chlorella vulgaris. Successful separation is possible in a broad range of environmental conditions and primarily depends on the nanoparticle-to-microalgae mass ratio, whereas the effect of pH and ionic strength are less significant when the mass ratio is chosen properly. The weakening of ionic concentration profiles at the interphase due to the successive addition of deionized water leads the microalgae to detach from the nanoparticles. The process works efficiently at the liter scale, enabling complete separation of the microalgae from their medium and the separate recovery of all materials (algae, salts, and nanoparticles). The current lack of profitable harvesting processes for microalgae demands innovative approaches to encourage further development. This application of magnetic nanoparticles is an example of the prospects that nanobiotechnology offers for biomass exploitation.

Using magnetic materials to harvest microalgal biomass: evaluation of harvesting and detachment efficiency

ABSTRACTUsing naked iron oxide (Fe3O4) and yttrium iron oxide (Y3Fe5O12) nanoparticles as flocculants, the harvesting efficiency of Chlorella vulgaris biomass was investigated. The harvesting process includes two steps, which are the separation of microalgae from the culture solution with the magnetic nanoparticles and then the separation of the algae from the magnetic nanoparticles. The optimal dosages and pH values for the magnetic harvesting of microalgal biomass were determined. Results showed that Y3Fe5O12 nanoparticles were more efficient in microalgal biomass harvesting than Fe3O4 nanoparticles. In an effort to achieve more than 90% of harvesting efficiency, optimal dosages for Fe3O4 and Y3Fe5O12 to harvest microalgal biomass were 10 and 2.5 g/L, while the appropriate pH values were 6.2 and 7.3, respectively. The harvesting efficiency of Fe3O4 and Y3Fe5O12 nanoparticles increased as the pH value decreased. The experimental results also showed that under a higher pH value Fe3O4 nanoparticles were much easier to be separated from the flocs than Y3Fe5O12. 62.9% of Fe3O4 nanoparticles could be de-attached from the aggregates, when the floc pH value reached 12.3.

PBE Modeling of Flocculation of Microalgae: Investigating the Overshoot in Mean Size Profiles

Microalgae is considered as a viable feedstock to biomass gasification. After synthesis in water medium, microalgae are separated and dried to a suitable degree to be fed to the gasification process. In order to achieve an efficient separation, a flocculation process is employed, in which microalgae primary particles aggregate and form larger clusters. Although flocculation is a well-established process, there are still some unknown issues related to it, that are worth further research. Experiments show that the mean size of clusters during flocculation goes through a maximum and then decreases with time. We refer to this pattern in the mean size profile as the overshoot. Studying this phenomenon is crucial since the size of clusters has a significant effect on the overall efficiency of the separation of microalgae from water. In this work, we aim at investigating the mechanisms behind the overshoot.The flocculation process is modeled as an aggregation-breakup system by using population balance equations (PBEs). The primary results show that the aggregation and breakup alone cannot lead to the overshoot in the mean size profile. Thus, we suggested three mechanisms that can lead to the overshoot: deposition of large clusters (DLC), restructuring of clusters (RC), and primary particle aggregation (PPA). These mechanisms were examined with numerical simulations and it was revealed that all three lead to the overshoot.

A Study on Techniques for Microalgae Separation and Lipid Extraction for Desmodesmus subspicatus

An alternative for production of biodiesel is the use of lipids from microalgae. The process has different steps such as microalgae cultivation harvesting, lipids extraction, and transesterification. One of the most important steps is the microalgae separation from the culture before lipid extraction. Thus, the purpose of the present study is to compare different methods of microalgae harvesting and total lipids extracting for freshwater Desmodesmus subspicatus microalga. The methods used for harvesting were chemical coagulation and electrocoagulation. Both methods achieved high values of recovery efficiency (90%). However, electrocoagulation was considered more attractive because of its lower power consumption and the requirement of high dosages of coagulants for chemical coagulation. Two methods of extraction, Soxhlet and ultrasound irradiation, were tested using different solvents. The highest lipid extraction (36%) was obtained with ultrasound irradiation and ethanol. Thus, ultrasound-assisted extraction appears to be an efficient method for lipid extraction from D. subspicatus.

Microalgae harvesting of <i>Nannochloropsis</i> sp. using polyethersulphone/lithium chloride/functionalised multiwall carbon nanotube membranes fabricated via temperature induced phase inversion and non-solvent induced phase inversion

Microalgae are a promising renewable source especially for producing biofuels and other high value products. Biofuel and biomass production involves several steps from cultivation, harvesting and extraction. Recent technology has used ultrafiltration membrane for microalgae harvesting but are faced with adverse effect of microalgae fouling. In the present study, Nannochloropsis sp. harvesting was performed using an ultrafiltration hybrid membrane made of polyethersulphone (PES) blended with the two additives namely lithium chloride (LiCl) and functionalised multiwall carbon nanotube (F-MWCNT). The membranes were prepared via two methods; non-solvent induced phase separation (NIPS) and temperature induced phase separation (TIPS). The membrane performances were evaluated in terms of membrane flux and fouling for the use of microalgae harvesting. The FESEM analysis showed that the morphology of the hybrid PES-MWCNT-LiCl membranes was very much influenced by the phase separation method. Flux rates of the membranes improved dramatically with increasing amount of additives when prepared using TIPS. A 100% microalgae separation from cultivated solution without major fouling (more than 80% flux recovery) was successfully achieved.

Investigation of microalgae growth on electrospun nanofiber mats

Due to their large inner surface, nanofiber mats are often used in tissue engineering and examined with respect to cell adhesion, e.g., for cultivation of fibroblasts. The combination of different polymers with a large contact area, however, could also be used for growth of different plants including green microalgae. Here, the cultivation of the microalga Chlamydomonas reinhardtii on different polymer substrates was examined. We investigated growth on two nanofiber mats consisting of polyamide (PA6) and polyacrylonitrile (PAN) and a polypropylene (PP) microfiber mat as substrates, compared with a pure multi-well plate. It was found that the algae were able to grow on all textile mats without change in morphology, indicating that all polymers were non-toxic to the cells. Thus, these nonwovens might be suitable filters for the separation of microalgae in biotechnological processes.

微藻磁分离进展研究

微藻能源是理想的可再生能源，能部分替代化石能源。然而其开发利用受微藻细胞小、浓度低导致的采收困难、采收成本高的限制。低成本、高效率地将微藻与水体有效分离是保障微藻推广利用的关键。本文分析了传统微藻分离技术存在的难点及研究趋势，讨论了国内外微藻磁分离技术研究现状及存在问题。为微藻水处理、资源回收等领域的进一步应用提供一定的基础理论研究保障。 Microalgae is an ideal renewable energy source that can partially replace fossil fuels. However, the difficulties and high cost of microalgae harvesting which caused by small cell and low concentration are the main constrains of microalgae utilization and further application. Hence, cost-effec- tive separation of microalgae from water body becomes the key issue to microalgae utilization. This paper analyzed the difficulties and research trends of traditional microalgae separation technology, discussed the current problems of microalgae magnetic separation technology, and further provided a theoretical basis for microalgae water treatment, resource recovery and its other application.

Continuous-flow sorting of microalgae cells based on lipid content by high frequency dielectrophoresis

This paper presents a continuous-flow cell screening device to isolate and separate microalgae cells (Chlamydomonas reinhardtii) based on lipid content using high frequency (50 MHz) dielectrophoresis. This device enables screening of microalgae due to the balance between lateral DEP forces relative to hydrodynamic forces. Positive DEP force along with amplitude-modulated electric field exerted on the cells flowing over the planar interdigitated electrodes, manipulated low-lipid cell trajectories in a zigzag pattern. Theoretical modelling confirmed cell trajectories during sorting. Separation quantification and sensitivity analysis were conducted with time-course experiments and collected samples were analysed by flow cytometry. Experimental testing with nitrogen starved dw15-1 (high-lipid, HL) and pgd1 mutant (low-lipid, LL) strains were carried out at different time periods, and clear separation of the two populations was achieved. Experimental results demonstrated that three populations were produced during nitrogen starvation: HL, LL and low-chlorophyll (LC) populations. Presence of the LC population can affect the binary separation performance. The continuous-flow micro-separator can separate 74% of the HL and 75% of the LL out of the starting sample using a 50 MHz, 30 voltages peak-to-peak AC electric field at Day 6 of the nitrogen starvation. The separation occurred between LL (low-lipid: 86.1% at Outlet # 1) and LC (88.8% at Outlet # 2) at Day 9 of the nitrogen starvation. This device can be used for onsite monitoring; therefore, it has the potential to reduce biofuel production costs

Flotation separation of marine microalgae from aqueous medium

Harvesting of oleaginous marine microalgae by dewatering is an important step for cost-effective algal biomass feedstock production. This paper reports separation of marine microalgae (Tetraselmis sp. M8) from aqueous medium by froth flotation using various collectors (surfactants) with equal carbon chain length, such as dodecyl pyridinium chloride (DPC), N-dodecylpropane-1,3-diamine hydrochloride (DN2), dodecyl amine hydrochloride (DAH), and sodium dodecyl sulphate (SDS), at different pHs. Algal hydrophobicity, froth stability, and surfactant precipitation were characterised. The laboratory-scale mechanical flotation tests showed that at natural pH 9.5 and a lower pH, DPC outperformed DAH, DN2 and SDS in separating Tetraselmis sp. M8 from seawater. DPC was capable of rendering the microalgae hydrophobic, producing metastable froth, and dissolving readily in water, which are all desirable features of a collector for flotation separation of microalgae from water. Use of DPC at 15 ppm in pilot-scale Jameson cell flotation tests for M8 after outdoor cultivation led to a 23-fold increase in algal concentration with over 99% algal recovery. (C) 2015 Elsevier B.V. All rights reserved.

A Review of Applications of Rotating and Vibrating Membranes Systems: Advantages and Drawbacks

Dynamic filtration (DF) consists in creating a high membrane shear rate by disks rotating near a fixed membrane or by rotating or vibrating membranes. The shear rate can exceed 3 105s-1 in some modules and significantly increases permeate flux and membrane selectivity as compared to cross flow (CF) devices. This paper describes several DF industrial modules and gives equations for calculating shear rates at rotating and vibrating membranes. It reviews 23 recent articles from 2008 to 2014, dealing with diverse applications: separation of microalgae from sea water by UF, clarification of rough beer, concentration of CaCO3 suspensions, treatment of dairy effluents and shipboard wastewaters, inulin extraction from chicory juice, treatment of oil field water, and separation of bovine albumin from yeast. In several applications, the maximum permeate flux at initial concentration ranged from 270 to 760 Lh-1m-2. Modules with ceramic membranes rotating around several shafts inside a housing seem to be preferable to the concept of multi-compartments modules with metal disks rotating between fixed membranes. Since the cost of DF modules is higher than that of spiral wound ones, it is better to apply DF to ”end of pipe treatment” after an initial concentration by CF.

Purification of microalgae from bacterial contamination using a disposable inertia-based microfluidic device

Microalgae are a promising source of bioactive ingredients for the food, pharmaceutical and cosmetic industries. Every microalgae research group or production facility is facing one major problem regarding the potential contamination of the algal cell with bacteria. Prior to the storage of the microalgae in strain collections or to cultivation in bioreactors, it is necessary to carry out laborious purification procedures to separate the microalgae from the undesired bacterial cells. In this work, we present a disposable microfluidic cartridge for the high-throughput purification of microalgae samples based on inertial microfluidics. Some of the most relevant microalgae strains have a larger size than the relatively small, few micron bacterial cells, so making them distinguishable by size. The inertial microfluidic cartridge was fabricated with inexpensive materials, like pressure sensitive adhesive (PSA) and thin plastic layers, which were patterned using a simple cutting plotter. In spite of fabrication restrictions and the intrinsic difficulties of biological samples, the separation of microalgae from bacteria reached values in excess of 99%, previously only achieved using conventional high-end and high cost lithography methods. Moreover, due to the simple and high-throughput characteristic of the separation, it is possible to concatenate serial purification to exponentially decrease the absolute amount of bacteria in the final purified sample.

Effects of dissolved organic matter and suspended solids on the magnetophoretic separation of microalgal cells from an aqueous environment

Magnetic seeding of microalgal cells is required prior to the successful implementation of magnetophoretic separation to harvest microalgae from an aqueous environment. Here, poly(diallyldimethylammonium chloride) (PDDA) forms with four different molecular weights were used to surface functionalize iron oxide nanoparticles (IONPs) to promote their attachment onto the cells by electrostatic interaction. We also investigated the effect of suspended solids and natural organic matter (NOM), which are normally found in fish farm water, on the magnetic seeding process. Dynamic light scattering (DLS) and electrophoretic mobility measurement were used to confirm the successful IONP functionalization by PDDA. For particle imaging, both electron and optical microscopes were used to monitor the IONP attachment on microalgal cells. For low particle-to-cell ratios of 10,000:1 or below, the effects of NOM and suspended solids on magnetophoretic separation of microalgae were obvious, with a cell separation efficiency that rarely exceeded 20%. For a particle-to-cell ratio in the intermediate range, the formation of large clusters composed of IONPs-suspended solids/NOM-microalgal cells (which were responsive to the magnetic field) instead of the independent formation of IONPs-suspended solids and/or IONPs-NOM entities is the main reason for minimum interference of suspended solids and NOM on the magnetophoretic separation. For a particle-to-cell ratio of 20,000 or higher (equivalent to 100mg/L of IONPs), it was possible to achieve 98% separation efficiency even under the strong effects of suspended solids and NOM.

A cost-effective strategy for marine microalgae separation by electro-coagulation–flotation process aimed at bio-crude oil production: Optimization and evaluation study

Microalgae as the third generation of biomass sources for biofuel production has a promising future, but its economic challenges have not been resolved yet. One of the major challenges in order to practical implementation of biofuel production is separation of microalgae from culture medium, since this step devotes a significant part of the energy and time consumption. Although various methods have been reported for harvesting, electro-coagulation–flotation (EC) method was preferred due to the simplicity and capability of process scale up. In this study, the effect of three parameters, i.e., initial pH, electric current density and duration on microalgae separation efficiency and operating costs, as the response variables, was investigated by applying “Response Surface Methodology” (RSM) technique. It was revealed that duration was the most effective parameter on the microalgae separation efficiency, as well as the operational costs, wherein high efficiency was resulted in long duration. On the other hand, the high amount of electric current density caused to high coagulation, flotation rates, and also high power consumption. Although the pH of solution had a little impact on operating cost compared to the duration and current density, the natural condition, pH=6, was recommended. In optimal point; current density=1.6mA/cm2 for 17.65min, deprived of demanding to adjust pH, the microalgae separation efficiency was obtained 96.8%. Since the EC is a substitute for CC (chemical coagulation), its performance was evaluated on microalgae separation efficiency. The results demonstrated that the optimal coagulant concentration and pH was 450mg/l and 8 respectively. At the optimal conditions, microalgae separation efficiency was resulted in 85%. Consequently, due to less sensitivity to pH changes, more flexibility and lower cost, the EC was introduced as a more efficient technology than CC Technology. All of these benefits recommend this method as the promising technique of microalgae harvesting in large-scale.

Megasonic Separation of Food Droplets and Particles: Design Considerations

The design aspects for building a megasonic reactor for separation of food materials from liquid/liquid or solid/liquid mixtures are presented in this review. These aspects are based on the theoretical principles of acoustic particle manipulation such as the acoustic primary and secondary radiation forces, acoustic streaming and the properties of food materials. Key considerations for the design of megasonic reactors are reviewed, which include the transducer selection, positioning and alignment, as well as construction materials and geometry of transducers and reactor. The design of these reactors is discussed around various food applications including palm oil separation, milk fat separation and fractionation, yeast separation in fermentation processes and separation of microalgae.