Preparation and characterization of grafted nonwoven membranes for bioseparations

Protein purification plays a crucial role in biotechnology and biomanufacturing, where downstream unit operations account for 40%-80% of the overall costs. To overcome this issue, companies strive to simplify the separation process by reducing the number of steps and replacing expensive separation devices. In this context, commercially available polybutylene terephthalate (PBT) melt-blown nonwoven membranes have been developed as a novel disposable membrane chromatography support. The PBT nonwoven membrane is able to capture products and reduce contaminants by ion exchange chromatography. The PBT nonwoven membrane was modified by grafting a poly(glycidyl methacrylate) (GMA) layer by either photo-induced graft polymerization or heat induced graft polymerization. The epoxy groups of GMA monomer were subsequently converted into cation and anion exchangers by reaction with either sulfonic acid groups or diethylamine (DEA), respectively. Several parameters of the procedure were studied, especially the effect of (i) % weight gain and (ii) ligand density on the static protein binding capacity. Bovine Serum Albumin (BSA) and human Immunoglobulin G (hIgG) were utilized as model proteins in the anion and cation exchange studies. The performance of ion exchange PBT nonwovens by HIG was evaluated under flow conditions. The anion- and cation- exchange HIG PBT nonwovens were evaluated for their ability to selectively adsorb and elute BSA or hIgG from a mixture of proteins. Cation exchange nonwovens were not able to reach a good protein separation, whereas anion exchange HIG nonwovens were able to absorb and elute BSA with very high value of purity and yield, in only one step of purification.

Microfluidic microbial fuel cell fabrication and rapid screening of electrochemically microbes

The demand for novel renewable energy sources, together with the new findings on bacterial electron transport mechanisms and the progress in microbial fuel cell design, have raised a noticeable interest in microbial power generation. Microbial fuel cell (MFC) is an electrochemical device that converts organic substrates into electricity via catalytic conversion by microorganism. It has represented a continuously growing research field during the past few years. The great advantage of this device is the direct conversion of the substrate into electricity and in the future, MFC may be linked to municipal waste streams or sources of agricultural and animal waste, providing a sustainable system for waste treatment and energy production. However, these novel green technologies have not yet been used for practical applications due to their low power outputs and challenges associated with scale-up, so in-depth studies are highly necessary to significantly improve and optimize the device working conditions. For the time being, the micro-scale MFCs show great potential in the rapid screening of electrochemically active microbes. This thesis presents how it will be possible to optimize the properties and design of the micro-size microbial fuel cell for maximum efficiency by understanding the MFC system. So it will involve designing, building and testing a miniature microbial fuel cell using a new species of microorganisms that promises high efficiency and long lifetime. The new device offer unique advantages of fast start-up, high sensitivity and superior microfluidic control over the measured microenvironment, which makes them good candidates for rapid screening of electrode materials, bacterial strains and growth media. It will be made in the Centre of Hybrid Biodevices (Faculty of Physical Sciences and Engineering, University of Southampton) from polymer materials like PDMS. The eventual aim is to develop a system with the optimum combination of microorganism, ion exchange membrane and growth medium. After fabricating the cell, different bacteria and plankton species will be grown in the device and the microbial fuel cell characterized for open circuit voltage and power. It will also use photo-sensitive organisms and characterize the power produced by the device in response to optical illumination.