Exploration of 3D Phage-Based Biomolecular Filter for Filtration of Foodborne Pathogens in Large Volume of Liquid Streams
Type of DegreePhD Dissertation
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A three-dimensional phage-based biomolecular filter (3D filter) was designed and developed to capture, concentrate, and isolate foodborne pathogens from large volume of liquid streams with high throughput, such as liquid food and water used to process foods.The 3D filter consisted of E2 phage-immobilized magnetoelastic (ME) filter elements, a controlled magnetic field, and a 3D filter pipe system. Due to the high selectivity and specific binding affinity, the filamentous E2 phage was utilized to capture Salmonella typhimurium pathogens in large volume of liquid streams with high throughput. The ME filter elements were aligned in the 3D filter pipe system by the controlled magnetic field. The target pathogens can be captured by the ME filter elements in the 3D filter pipe system, while the debris and non-target pathogens would pass through the 3D filter system with the liquid steams. Therefore, the 3D phage-based biomolecular filter was developed for an anti-clogging specific filtration with a high throughput. In this dissertation, two generations of the 3D filter (3D filter 1.0 &2.0) were developed and tested. The 3D filter 1.0 system was formed by ME filter elements, supporting frames with solenoid coils, and a 3D filter pipe system. The ME filter elements were aligned on the supporting frames by electromagnetic field produced from the solenoid coils. The soft magnetic material of the supporting frames was selected from the commercial market, and the structure of the supporting frames was designed and fabricated. The magnetic field was simulated and measured by Ansys Workbench and Gaussmeter. For foodborne pathogens capturing experiments, the effect of temperature variation on the E2 phage and the Salmonella typhimurium suspensions was firstly tested in the 3D filter 1.0 pipe system, followed by Salmonella typhimurium capturing experiments. The increased capture rate was illustrated with the increased number of filter layers. However, the filtration of Salmonella pathogens was not realized due to the low density of aligned ME filter elements and the low capture rate. Because of the low capture rate, the filtering capability of ME filter elements was explored by 2D filter experiment, followed by the development of 3D filter 2.0 system without the supporting frames. For the 3D filter 2.0 system, a pair of permanent magnetic plates was used to align the ME filter elements in the 3D filter 2.0 pipe system instead of the solenoid coils. The development of the 3D filter 2.0 was divided into three stages, including the initial 3D filter 2.0, the large-scale 3D filter 2.0, and the multipipe-3D filter 2.0. The filtration of Salmonella pathogens was demonstrated by the initial 3D filter 2.0. The anti-clogging characteristic and high throughput performance were demonstrated by the large-scale 3D filter 2.0, as well as the filtering performance of Salmonella pathogens with the increased number and the total surface area of ME filter elements. The turbulent flow condition of pathogen suspensions and the capture rate were also simulated and discussed in the stage of initial 3D filter 2.0 and the large-scale 3D filter 2.0. In the third stage, the multipipe-3D filter system with circulation flow of pathogen suspensions was used to explore the filtering performance with the increased volume of liquid streams. The interaction between the cyclic times for 90% capture rate and the volumes of pathogen suspensions was investigated by the multipipe-3D filter system with circulation, which could be a reference to design the multipipe-3D filter system for a specific volume of pathogen suspensions.