# Microfluidic encapsulation of bacteria in emulsion droplets

Mohd Isa, Nur Suaidah (2020). Microfluidic encapsulation of bacteria in emulsion droplets. University of Birmingham. Ph.D.

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## Abstract

The encapsulation of bacteria in emulsion droplet has gained significant interest due to its various applications such as in the study of complex bacterial interactions and as a mean of protection for bacteria against harsh conditions. The application of droplet microfluidics allows for the encapsulation of bacteria in a highly controlled manner. Nevertheless, relevant studies of the effect of bacteria on emulsion stability remain scarce. Therefore, this thesis is focused on determining the effect of microfluidic-encapsulated bacteria on droplet stability and bacterial viability during ambient and cold temperature storage.

The study began by encapsulating bacteria in single water-in-oil (W/O) droplet. The inclusion of the Gram-negative E. coli with green fluorescent protein (E. coli-GFP) in W/O showed better droplet stability as compared to the Gram-positive L. paracasei as the droplet size distribution was maintained during storage at 25°C. Dead E. coli-GFP cells showed better stabilization effect as compared to live cells indicating the ability of dead cells to act as Pickering’s particles in stabilizing the interface of the droplet. Encapsulation in W/O caused a reduction in bacterial viability while promoting the formation of bacterial clustering.

The study is then followed by the encapsulation of bacteria in double water-in-oil-in-water (W$$_1$$/O/W$$_2$$) droplet. The ability of W$$_1$$/O/W$$_2$$ droplet in supporting bacterial growth was observed due to the presence of an outer W$$_2$$ phase. In addition, the controlled release of bacterial cells induced by osmotic alterations was also determined with a high bacterial release observed at high sodium chloride concentration and low Tween 80 concentration.

Finally, the stability of W/O and W$$_1$$/O/W$$_2$$ droplet during cold temperature storage were also investigated whereby storage in freezing temperature caused an extensive droplet destabilization. This lead to complete bacterial release into the W$$_2$$ phase upon thawing. The results obtained from these studies provide a better understanding of the feasibility of using emulsion droplet for bacterial encapsulation and controlled release that are beneficial for laboratory and industrial applications.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Supervisor(s):
Supervisor(s)EmailORCID
Vigolo, DanieleUNSPECIFIEDUNSPECIFIED
Konstantinos, GkatzionisUNSPECIFIEDUNSPECIFIED
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Chemical Engineering
Funders: Other
Other Funders: Ministry of Higher Education Malaysia (MOHE), Universiti Malaysia Terengganu (UMT)
Subjects: Q Science > QD Chemistry
Q Science > QR Microbiology
URI: http://etheses.bham.ac.uk/id/eprint/10112

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