1,049 research outputs found
Development of a continuous flow ultrasonic harvesting system for microalgae
2014 Fall.Microalgae have vast potential as a sustainable source of biofuel. However, numerous technoeconomic analyses have indicated that microalgae harvesting represents a critical bottleneck in the microalgae value chain in terms of energy requirements, capital cost and operating cost. This dissertation presents an approach that uses a combination of acoustophoretic, fluid mechanical, and gravitational forces toward the development of a continuous flow microalgae harvesting system. Ultrasonic Standing Waves have been widely reported in the literature as an approach to manipulate particles in a fluid, a phenomena known as acoustophoresis. These waves exert an acoustic force that agglomerate the cells in the wave nodes or antinodes and the force is directly proportional to the cell acoustic contrast factor. Ultrasonic microalgae harvesting is a promising low cost and low energy approach. However, a better understanding of the acoustic properties of microalgae is essential for the development of this technology. Accordingly, a major component of this work focused on accurately quantifying the acoustic contrast factor of microalgae cells of Nannochloropsis oculata, Nannochloropsis gaditana, Phaeodactylum tricornutum and Chlamydomonas reinhardtii by measuring the average cell density and speed of sound using a vibrating tube densitometer. The results indicate a linear correlation of density and speed of sound as a function of cell concentration. Using this correlation, non-scattering volume average relationships were used to compute density and speed of sound for the average algal cell. The acoustic contrast factor was estimated to be between 0.04 - 0.06 for microalgae cells in their corresponding growth media. Second, particle tracking velocimetry was used to determine the magnitude of the acoustophoretic force. In these studies, in addition to microalgae cells, polyamide seeding particles were used as a surrogate. The results obtained conclude that the maximum acoustophoretic forces are approximately 5 pN for Chlamydomonas reinhardtii cells and the results also show that there is change in the acoustic contrast factor from positive to negative with lipid accumulation. This dissertation also presents a novel device for the acoustic harvesting of microalgae. The design is based on using the acoustophoretic force, acoustic transparent materials and inclined settling (Boycott effect). A filtration efficiency of 70% ± 5% and a concentration factor of 11.6 ± 2.2 were achieved at a flow rate of 25 mL • min-1 and an energy consumption of 3.6 ± 0.9 kWh • m-3. The effects of the applied power, flow rate, inlet cell concentration and inclination were explored. It was found that the filtration efficiency of the device is proportional to the power applied. However, the filtration efficiency experienced a plateau at a 100 W • L-1 of power density applied. The filtration efficiency also increased with increasing inlet cell concentration and was inversely proportional to the throughput of the device as measured flow rate. It was also found that the optimum settling angle for maximum concentration factor occurred at an angle of 50° ± 5°. At these optimum conditions, the device had higher filtration efficiency in comparison to other similar devices reported in the previous literature
A high-throughput approach to vaccine bioprocess development
Vaccination is currently the predominant tool in the prevention of infectious disease. Each year, an estimated 2-3 million lives are saved worldwide and infant mortality has been significantly reduced. Despite substantial recent advances, vaccine manufacturing can still be laborious owing to difficulties in development, lengthy clinical trials, and stringent regulations.
In light of the SARS-CoV-2 (Covid-19) pandemic, the need for a development platform which can rapidly screen potential candidates and/or a vaccine scaffold capable of adaptability to new disease targets has never been more apparent. To meet this need, the breadth of vaccine types under exploration has rapidly expanded. DNA and RNA vaccines offer the opportunity for rapid manufacture but can be poorly immunogenic, whilst subunit vaccines can require complex processing. Virus-like particles (VLPs) have the potential to address these two factors.
Tandem Core VLPs, expressed in the methylotrophic yeast Pichia pastoris, are an exciting alternative to current manufacturing methods. They have excellent potential, both as standalone vaccines for the virus from which they are derived, or as scaffolds for the display of foreign antigens. The hepatitis B core antigen (HBC) can spontaneously self-assemble, forming icosahedral particles that are inherently immunogenic. Tandem Core HBC VLPs have been genetically modified in the major insertion region (MIR) enabling surface display of up two epitopes of interest when assembled.
For HBC VLPs to be considered a viable vaccine candidate, their bioprocessing must be optimized. Currently, there are various issues to address including problems with formation, solubility and immunogenicity, which are often clone dependent. In this work, Tandem Core VLPs, consisting of genetically linked HBC monomers carrying different epitopes in the MIR will be used to develop a high-throughput platform and explore the impact of different inserts on VLP production and processing. Influenza will be used as a model pathogen owing to its persistence as a public health threat.
The aim of this work is to develop a vaccine platform, defined by Adalja et al., (2019) as “a technology in which the underlying, nearly identical mechanism, device, delivery vector or cell line was employed for [design of] multiple target vaccines”. The equipment and methods developed in this work were considered to enable: (1) thorough investigation of three HBC VLP candidates in an attempt to identify a universal bioprocess, irrespective of surface displayed epitopes; (2) formation of a small-scale high throughput platform which could be implemented for rapid screening of new disease targets or to allow fine-tuning of processes for epitope-dependent optimisation.
After initial studies using an ‘empty’ HBC VLP (HBC-K1,K1), the ambr®250 modular was used to investigate upstream bioprocessing of three influenza specific candidates (HBC -HA2,3M2E, -LAH3,K1 and -3M2E,K1), exploring different fermentation induction strategies and to identify epitope related differences. Following this, the most readily soluble candidate (HBC-LAH3,K1) was selected for further upstream optimisation combining ambr® 250 experimentation with statistical Design of Experiments (DoE). An improved process was identified enabling an increase in VLP titre, a 34% increase in biomass compared to the initial condition, and a 6% decrease in process time compared to methanol induction. This process was then applied to the production of the alternative VLP constructs. The improved feeding regime resulted in higher biomass and soluble HBC yield for all three VLPs.
Subsequent downstream process studies on the primary recovery of VLP candidates was then necessary to account for the reduced volumes associated with miniaturised fermentation studies, and to bridge the gap between upstream processing and purification. Building on previous work, a high-throughput, small scale cell disruption method was investigated using Adaptive focused acoustics®. A 96-well plate workflow was demonstrated, enabling suitable VLP release and recovery with a ~99.7% reduction in sample volume, in comparison to high pressure homogenisation (HPH).
Finally, chromatography screening was undertaken using high-throughput PreDictor® plates to rapidly identify separation conditions for the various vaccine candidates. Studies were conducted to investigate suitable resins and binding/elution conditions and to determine the influence of the physicochemical properties of the displayed epitopes on separation performance. Multiple resins were identified as being suitable for VLP purification, and results were useful to manipulate chromatographic separation (5mL column scale) conditions for the VLPs to achieve improved product yield and purity profiles.
Overall, this research suggests that a high-throughput vaccine development platform can be realised through the integration of numerous small-scale single-use equipment, techniques and methodologies. Namely, the use of the ambr®250 bioreactors, AFA® cell disruption in 96-well plates and 96-well PreDictor™ resin plates. Combined with statistical DoE, this platform can be used to rapidly optimise production and purification conditions for novel vaccine technologies such as HBC Tandem Core VLPs. The improved bioprocessing of these constructs paves the way for future vaccine candidates which exploit HBC as a vaccine scaffold. These findings have implications for reducing the time taken to develop vaccine manufacturing processes and prepare for disease outbreaks based on ‘Pathogen X’
Numerical and experimental design of ultrasonic particle filters for water treatment
Due to limited water resources available in the world and the ever growing world population, there is an increasing need for water recycling, recovery and multi-sourcing strategies. One of the new physical process technologies being investigated for water purification and/or constituent recycling is ultrasonic particle separation. This technology is especially interesting for harvesting particles with an almost neutral buoyancy. An ultrasonic particle filter does not use a filter medium, like sand or a membrane, but filters on a basis of acoustic forces in ultrasonic standing waves, which are able to immobilise particles in flowing water. The objective of this study was to develop an ultrasonic separation device for particle recovery and water purification. This separator should be fit for industrial applications treating cubic meters of water per hour. In order to reach this objective, a combined numerical-experimental approach was proposed to develop a model-based design of an ultrasonic separator. Each individual component of this separator was modelled using a finite element (FE) approach. The numerical simulations were continuously cross-checked with experiments in order to find the best solution possible. In this thesis, the source of the acoustic wave is a piezoelectric transducer attached to a glass matching layer of the acoustic cavity, which couples the transducer to the fluid inside the cavity, forming an acoustic resonator/separator. In order to obtain a valid FE transducer model, a limited set of material parameters for the piezoelectric transducer were obtained from the manufacturer, thus preserving prior physical knowledge to a large extent. The remaining unknown parameters were estimated from impedance (admittance) analysis combined with a numerical optimisation routine using 2D and 3D FE models. Thus, a full set of physically interpretable material parameters was obtained. The approach provided adequate accuracy of the estimates of the material parameters, near 1%. A similar approach as used for the transducer was applied to an existing ultrasonic separator, again preserving known physical parameters and estimating the remaining unknown or less certain parameters. The results showed that the approach led to a fully calibrated 2D model of the emptyseparator, which was subsequently validated with experiments on a filledseparator chamber. The large sensitivity of the separator to small variations indicated that either such system should be made and operated within tight specifications to obtain the required performance. Alternatively, the operation of the system should be adaptable to cope with a slightly off-spec system, requiring a feedback controller. Starting from a fully characterised existing separator with all material parameters found so far, the subsequent step was the actual design of, or extrapolation to, a new separator. A basic design for an industrial scale acoustic separator was obtained based on simulated flow characteristics inside the separation chamber, on acoustic analysis within the chamber and simulated particle trajectories combining these two analyses. Results showed that positioning the piezoelectric transducer surfaces perpendicular to the flow direction and introducing chamber partitioning with multiple flow lanes to enforce laminar flow, resulted in high particle retention. The average particle displacement was found to be related to acoustic pressure in the fluid, showing large retention at peak pressures above 1 MPa or average pressures above 0.5 MPa for small (10 µm), near buoyant (1100 kg/m3) particles at a flow speed of 3.5 cm/s, thus providing comprehensible criteria for subsequent optimisation. This basic ultrasonic standing wave separator design was optimised with respect to separation efficiency, throughput and energy consumption. The methodology, using a design of experiments (DOE) approach, showed that it was possible to improve system performance based on acoustic pressure profiles, separation efficiency and flow robustness. Compromising the energy consumption and aiming for maximum separation efficiency with a laminar stable flow up to 5 ml/s resulted in a separator with inner dimensions of 70 mm length, 20 mm width and 28.5 mm height using two transducers perpendicular to the direction of flow and three parallel flow lanes with 9.5 mm height each. The lowest power consumption (with an average of 30 W) with adequate pressure to trap the particles was obtained when it was not operated at the main eigenfrequency. Finally, this new ultrasonic particle filter was built and evaluated experimentally. The particle filter was a three channel device, manufactured from glass with four in/outlet ports made of ABS. It was operated in sequenced batch mode and the separation efficiency was determined at three flow rates ranging from 1 to 3 ml/s, using a stock suspension of insoluble potato starch of 1 g/l (1000 ppm). Concentrations of stock, filtrate and concentrate were measured using a turbidity meter and significant effects of acoustic particle concentration were measured at both outlets of the process. The maximum filtration efficiency and concentration efficiency were 54% and 76%, respectively. The performance found was lower than the 100% that was expected for 10 µm particles from the model based design study. The deviation in performance is mainly a result of (i) the pulsation of the feed pump, (ii) differences between the model and the actual prototype, (iii) the limited power supply of only 10 W used and (iv) (too) small particles, below 10 µm, occurring in the starch suspension. The best dimensions for an acoustic separator were obtained, but thus far operational characteristics were not yet studied. Operational characterisation and optimisation is the last step in the process of obtaining the best possible solution for operation. With the aim to achieve a high separation efficiency with minimal energy consumption, a model-based open-loop switching control strategy was designed for the commercially available BioSep, using a numerical-experimental approach. Firstly, a dynamic BioSep model structure was derived from mass balances and its system properties were studied. Then, the unknown system parameters were estimated from steady state and dynamic experimental data and subsequently, the switching times of the control input were determined. The model with switching control outputs was then validated by experiments. Finally, the control strategy was implemented in an experimental setup and tested using suspended potato starch. Results showed that the optimal control strategy reached a mass separation efficiency of 96%, which was an improvement of 4% with respect to the initial settings, while using less energy. Concluding, a stepwise numerical-experimental approach to acoustic separator design was presented in this study. The minimum power required was estimated to be 22-34 W, resulting in an average electric energy consumption of 1-1.5 kWh/m3. The practical concentration efficiency obtained was 76% at a flow rate of 2 ml/s and a filtration efficiency of 54% at 1 ml/s with a real power input of 8.8 W. An optimal open loop control strategy showed that it is possible to operate an acoustic separator with high separation efficiency using the least power possible. Parallelisation, instead of enlarging the separator, is recommended to scale this system up to larger, industrial flows.</p
A study of the application of ultrasonic standing waves to the segregation of fine biological particles from liquids
This thesis describes research to evaluate the application of megahertz (1 to 10 MHz) ultrasonic standing waves to the segregation and separation of fine biological particles, in the size range of 0.1 to 10 μm, from liquids. Research has focused on the development of an alternative separation technique through the ability to selectively manipulate delicate, highly hydrated particles typical of many biological process streams where the sedimentation characteristics of the particles preclude traditional centrifugation-based separation methods and the requisite for non-invasive in line processing rules out filtration. A survey of both acoustic and ultrasonic research concentrating on the application of ultrasonic energy to processes involving biological particles has been carried out. An in-depth analysis of the theories of ultrasonics in relation to the stated aims of the work is presented in which the mechanisms controlling the migration of fine particles under the influence of a megahertz frequency standing wave field are discussed. Results of investigations to determine the feasibility of concentrating micron-sized particles in a standing wave field arc presented. These confirm that the small-scale separation of biological particles is achievable. The subsequent design of an experimental separation device and detailed experiments to elucidate the parameters of importance in determining the segregation of biological particles from liquids using this apparatus are described. Ultrasonic power input and fluid velocity were found to be the most critical process parameters and operational constraints as functions of particle size and ultrasonic frequency were identified. The design and development of a novel laser scanning technique for the monitoring of the migration of particles in an ultrasonic standing wave field is presented. Data obtained using this equipment has been used when discussing the design of large-scale continuous solid-liquid separation devices. Details of an ultrasonic system for the non-invasive, in-situ sample preparation of material for dynamic laser light scattering analysis of particle size distributions in the monitoring and control of bioprocesses are presented together with data from experimental trials. Results showed this to be a promising method for rapid and controlled sample preparation and well suited to handling process streams containing heterogeneous particle sizes. The thesis concludes by giving consideration to the necessary future work and to the application of the techniques described in the thesis to relevant biological separation problems
Micro/Nano-Chip Electrokinetics
Micro/nanofluidic chips have found increasing applications in the analysis of chemical and biological samples over the past two decades. Electrokinetics has become the method of choice in these micro/nano-chips for transporting, manipulating and sensing ions, (bio)molecules, fluids and (bio)particles, etc., due to the high maneuverability, scalability, sensitivity, and integrability. The involved phenomena, which cover electroosmosis, electrophoresis, dielectrophoresis, electrohydrodynamics, electrothermal flow, diffusioosmosis, diffusiophoresis, streaming potential, current, etc., arise from either the inherent or the induced surface charge on the solid-liquid interface under DC and/or AC electric fields. To review the state-of-the-art of micro/nanochip electrokinetics, we welcome, in this Special Issue of Micromachines, all original research or review articles on the fundamentals and applications of the variety of electrokinetic phenomena in both microfluidic and nanofluidic devices
Data Acquisition Applications
Data acquisition systems have numerous applications. This book has a total of 13 chapters and is divided into three sections: Industrial applications, Medical applications and Scientific experiments. The chapters are written by experts from around the world, while the targeted audience for this book includes professionals who are designers or researchers in the field of data acquisition systems. Faculty members and graduate students could also benefit from the book
Proceedings of the Scientific-Practical Conference "Research and Development - 2016"
talent management; sensor arrays; automatic speech recognition; dry separation technology; oil production; oil waste; laser technolog
Investigating the capability of pulsed ultrasound technology in improving the performance of surface water treatment systems
Surface water is an important resource for drinking water production. Due to increasing contamination caused by floods and urbanisation, the quality of surface water continues to deteriorate. This problem is currently addressed by increasing the chemical additives used in water treatment processes. This practice introduces
health-related problems such as the formation of disinfection by-products (DBPs) and the increase of Al residues. The application of physical rather than chemical
treatments is a logical solution to the above problems. When evaluating various physical treatments, ultrasound appears a sensible choice for improving contaminants
removal from surface water.
While numerous studies have addressed the application of ultrasound technologies in water treatment, most of these studies used single contaminant synthetic water samples which does not present a realistic assessment. The key focus
of this study is using natural water samples with a representative mixture of contaminants.
The main challenge cited regarding ultrasound application is high energy consumption. To tackle this issue, the use of pulsed ultrasound has been proposed in this study. An improved calorimetric technique has been developed and tested to provide a fair evaluation of energy conversion in ultrasonic reactors. Sonochemical efficiency (SE) based on •OH and H2O2 measurements for the ultrasonic system
along with the new calorimetric technique were employed.
The optimal location of pulsed ultrasound technology within the surface water treatment process was identified using natural water samples with different carbon origins. The optimal location was found to be prior to the coagulation stage. The operation of pulsed ultrasound in this location was optimized with regards to power, treatment time and pulse format. Total coliform, DOC and UV-vis measurements
were applied along with chemical fractionation techniques to establish the optimal operating conditions. Overall, ultrasound treatments resulted in 10-70% of microbial
removal and 7-15% of DOC removal with a decrease in the aromatic hydrophobic DOC and a marginal increase in the hydrophilic DOC. The effectiveness of these conditions in promoting further removal of contaminants with alum coagulation was also examined.
Turbidity, DOC removal and residual Al were measured for alum coagulation with and without pulsed ultrasound pre-treatment. Response optimization showed
that pulsed ultrasound pre-treatment increased turbidity and DOC removal and reduced residual Al. Analysis of downstream effects revealed that pulsed ultrasound
pre-treatment increased total coliform removal, decreased trihalomethane formation potential (THMFP) and improved the settling of coagulation sludge.
A large-scale laboratory magnetostrictive ultrasonic reactor operated on square-pulse waveform was designed and tested. It was observed that scaling up to 15 L improved sonochemical efficiency of ultrasonic reactor. Using a reactor tank with 45 inclined sides further improved sonochemical efficiency. The larger design was more energy efficient in removing water contaminants compared to the small scale. This study confirmed that pulsed ultrasound is an effective tool for improving surface water treatment system, however further investigations required using other
coagulants and monitoring of subsequent effects on other DBPs. It is also important to evaluate the performance and economic viability of the large scale reactor in continuous systems
The development of a novel on-line system for the monitoring and control of fermentation processes
A thesis submitted to the University of Luton for the degree of Doctor of PhilosophyThis thesis describes the development of a computer controlled on-line system for fermentation monitoring and control. The entire system consists of a laboratory fermenter, flow injection system (four channels), a newly designed on-line filter, biomass analysis channel, pH and oxygen controllers as well as a spectrophotometer. A new design of gas driven flow injection analysis (FIA) allows a large number of reagents to be handled. The computer-controlled four channel PIA system is well suited for sequential analysis, which is important for fermentation on-line mOnitoring. The system can change the wavelength of the spectrophotometer automatically for each PIA channel, which makes the system powerful and flexible. A high frequency, low energy ultrasonic filter was modified and applied to the system for on-line mammalian cell culture sampling without breaking the sterile barrier. The results show that this novel application of ultrasonic filter technology results in higher efficiency and reliability and a longer life cycle than other types of filter. All the operations of the analytical system are controlled by a Macintosh computer (Quadra 950). The control program was written in LabVIEW which is a graphical programming language and well applicable to fermentation control. The software communicates with detectors, data acquisition, data analysis and presentation. The system can programmatically control up to 50 devices. Mammalian cell batch culture was used as an example of the application of the system. The system consists of a laboratory fermenter with a continuous sample withdrawal filter and an analysis system where glucose, lactate and ammonia, lactate dehydrogenase and biomass were measured. Cell viability was estimated by microscopic assay with trypan blue. pH and Oxygen were also measured. The system response was fast and yields a large number of reliable and precise analytical results which can be of great importance in the monitoring and control of mammalian cell culture conditions
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