Porous scaffolds for 3D biocatalysis using biofilms

Supervisors: Dr T Overton, Dr F Fernandez-Trillo and Prof M Simmons
Biocatalysis is an advantageous process for the production of some chemicals; it offers stereoselectivity and stereospecificity when compared to many chemically-catalysed reactions, and so is frequently used for the production of pharmaceuticals. We have developed novel recombinant biofilm platforms for biocatalysis that outperform immobilised enzymes, cell lysates and whole planktonic cells in the biocatalytic generation of 5-halotryptophans, which are important pharmaceutical precursors.
In this project we will prepare a library of porous polymer scaffolds (aka polyHIPEs) for supporting growth of recombinant bacterial biofilms. It is desirable to move from current planar biofilm supports to 3D porous scaffolds in order to increase catalyst loading and overall surface area, thus improving reaction efficiency. The project will comprise four research objectives:
O1. 1st generation polyHIPE: We will prepare and characterise a series of polymeric porous scaffolds with different monomer composition to tailor scaffold pore size, flow‐through and structural integrity. Porosimetry, Electron Microscopy and Elemental analysis will be used to characterise the scaffolds.
O2. Biofilm growth and catalysis: E. coli biofilms expressing biocatalytic enzymes will be grown on the scaffolds generated in O1. Three main parameters will be tested: Strain (varying surface characteristics such as protein adhesin and extracellular matrix expression); biocatalytic enzyme (testing different reaction systems chosen from an industrially‐relevant portfolio); and growth conditions (such as medium osmolarity, nutrient concentrations, carbon source, temperature etc., all of which are known to influence biofilm formation). Bacterial localization and physiology will be monitored using laser scanning confocal microscopy, and biocatalysis will be measured at the level of reaction rate using HPLC or comparable techniques (depending upon reaction) and spatially using confocal Raman microscopy.
O3. 2nd generation polyHIPE: At this stage we will modify the best polyHIPEs from O1 and O2 with relevant functionalities for cell attachment and biofilm formation such as carbohydrates, peptides and/or nucleic acids. Characterisation of these scaffolds in terms of physical properties and biofilm growth and catalysis will be done using the techniques optimised in O1 and O2. We will evaluate how different functionalities affect biofilm formation across a range of strains.
O4. Lab‐scale Bioreactor Design and Development: Scaffolds and bacteria developed in O1‐O3 will be used to build a flow‐through bioreactor in packed bed, trickle bed or monolith configurations. Support geometry and size will be varied along with flow rate, retention time and other bioreactor operational parameters.
Excellent students are invited to apply, with an Undergraduate Honours degree with a minimum classification of a 1st or equivalent and an English Language qualification for international students. Applicants should have a biosciences, chemical engineering, bioengineering, biotechnology or chemistry background and be interested in interdisciplinary research.
Please contact Dr Tim Overton with your CV by email: [Email Address Removed]