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Author ORCID Identifier

https://orcid.org/0000-0002-5782-7389

Document Type

Campus-Only Access for Five (5) Years

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Food Science

Year Degree Awarded

2019

Month Degree Awarded

September

First Advisor

Lili He

Subject Categories

Biotechnology | Food Chemistry | Food Microbiology

Abstract

Microbiological hazard is one of the most important aspects of food safety, with millions of foodborne illnesses occurring annually. It is a huge issue for public health because of the common presence of pathogens in the environment and food systems and easily exposed to human during harvest, processing, food handling besides consuming the food. Moreover, the tremendous varieties of different bacterial strains bring complexities to the survival and presence of pathogens in different food matrices and poses a great challenge to the development of detection methods. Rapid bacterial detection methods are critical for quick identification of target pathogens, and of great research interest over the decades. Surface-enhanced Raman spectroscopy (SERS) is the integration of nanotechnology to the vibrational Raman spectroscopy techniques, which provide signature spectral information of the target analyte and has been widely applied to the characterization and detection of microorganisms. We have developed filter-based SERS mapping assays for detection of total and specific bacteria in water and food systems, which requires simple sample preparation procedures and can achieve low detection limit with adjustable sample volume. With the integration of 4-mercaptophenylboronic acid as a probe and label, which can bind to the diol structure on the bacterial cell walls, we were able to detect the total bacterial in water using Escherichia coli as a model bacterium. We also successfully applied an aptamer specifically designed for Salmonella enterica serovar Enteritidis to develop a filter-based rapid screening assay using an ultra-fast benchtop Raman imaging instrument, which can generate mapping consists of 625 data points in less than 8 minutes. This method can rapidly identify and estimate the level of target pathogen in pure water and produce rinsed water within 3 hours. The success of combining the filtration technique with SERS mapping demonstrates the versatility of the filtration system to be integrated with multiple SERS labels to serve different bacterial detection purposes. The result of the studies provides useful implications for future applications of the filtration technique in SERS mapping and opens a new gate for fast bacterial screening method using SERS.

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