Bacteria offer an efficient, green, and versatile platform to perform a range of industrial processes,

however their integration into these systems faces challenges related to handling and processing

of bacteria as well as culture stability. Biocoatings, which encase live, metabolically active

bacteria in porous polymeric films, present an innovative solution to enhance culture stability,

increase productivity, and reduce establishment time. However, the film formation process

required to produce biocoatings can induce desiccation stress, which reduces bacterial viability.

Furthermore, achieving sufficient long-term permeability for sustained metabolic activity within

the coating is often challenging. The encapsulation of bacteria within hydrogel capsules before

casting into biocoatings is presented as a strategy to mitigate these issues. The capsules

are intended to create macro-scale porosity within the coating while limiting desiccation for

encapsulated bacteria during film formation.

Covalent hydrogel capsules were developed using a poly(ethylene-glycol) diacrylate (PEGDA)

monomer solution dispersed in an oil phase containing a UV photoinitiator. Capsules were

then produced upon UV irradiation. This method led to the discovery of three distinct capsule

microstructures: Honeycomb, Sponge, and Solid capsules, with each offering varying water

holding capacities and porosity. A novel capsule formation mechanism based on the diffusion limited

aggregation of PEGDA microbeads was proposed following cryo-SEM imaging and

simulations.

A resazurin metabolic assay was developed to quantify bacterial viability post-encapsulation

across multiple species. This revealed that physical barriers to radical damage, such as the

mycobacterial capsule, were the most effective protective mechanism against PEGDA radicals,

outperforming inherent enzymatic and chemical defences found in E. coli and Pseudomonas.

Finally, free-standing hydrogel/coating composites with tunable mechanical properties and

permeability were created. These composites maintained permeability to small molecules while

effectively adhering the capsules to the substrate. Under high relative humidity, they sustained

metabolically active bacteria. The research also explored a desiccation-free latex gelation

method, enabling successful incorporation of capsules and bacterial growth within biocoatings.

This work provides a foundational framework for developing multifunctional, living materials

by integrating hydrogel capsules into biocoatings, significantly expanding their potential

applications.