Research Group: Biotechnology and Bioprocess Engineering (BBE)
Our programme is concerned with novel and fundamental approaches to certain specific problems in biotechnology, separation and industrial waste water treatment. The processes we study are multiphase, often biochemical in nature, and most of them involve separations. This involves understanding the interface between phases-usually fluid-fluid interfaces- across which all separation processes take place. In addition we have a new and growing interest in tissue engineering: developing viable substitutes for damaged human tissues and organs.
We are very interested in biotransformation processes and in downstream separation of their products, which are often of medical interest. Organic chemistry can provide molecules with suitable structures, but invariably produces a mixture of chiral (optically active) compounds; generally only one of them is biologically active. In contrast, biological systems are capable of producing the active chiral compound without the inactive mirror image: they are stereo-specific.
In some cases the materials involved are more soluble in the organic phase than in water, and can also be toxic to biological entities. Therefore, we cannot use conventional bioreactors, and are developing a range of novel ones. One type uses microfiltration membranes; another creates a reversed micelle structure (water in solvent microemulsions) around cells so that toxic products can be removed rapidly from the aqueous shell into the bulk organic phase. A third is a membrane bioreactor in which silicone rubber separates a solvent and an aqueous phase, while allowing organic substrates and products to permeate. To evaluate them we are working with model systems - for instance, producing chiral epoxides, precursors of beta-blockers, with Mycobacterium and Pseudomonas.
There is a thriving area of research on the fundamentals of separation. We are studying the mechanisms of turbulence at the interface and the effect on mass transfer of both interfacial convection (with and without surfactants) and gravitational convection. The latter involves experiments under micro-gravity conditions in parabolic flights provided by the European Space Agency.
Amongst the systems we study in detail are liquid membranes, reversed micelles, aphrons and ion exchange microparticles. They share a suitability for achieving separations where feed solutions are very dilute. Colloidal liquid aphrons (CLAs) are oil in water micro-emulsions in which oil droplets of 1 to 10 µm diameter can selectively remove valuable products like antibiotics from fermentation broths. CLAs are very versatile: adding a quaternary ammonium compound allows extraction of polar solutes. What is more, their surface areas are so large that small contactors with contact times less than a second are effective.
An example of one of our environmental projects is providing metal-plating companies and tanneries with a cheap process to separate and recover heavy metals like cadmium and nickel form their effluent. Traditional technology to recover the metals is uneconomic, largely because the concentrations of heavy metal ions in effluent are very low. Using a combination of chemical and biochemical methods these ions are reduced to very low levels, and the recovered metals can then be recycle.
Other projects investigate anaerobic treatment of waste waters, which results in very little sludge for disposal and actually produces energy. Our Extractive Membrane Bioreactor provides a novel way of treating toxic, non-polar organic materials in chemical industry waste waters, extracting them into a controlled aqueous biomedium for decomposition. It is currently on trial at several UK manufacturing sites.
Finally, our new tissue engineering activity focuses on growing complex three-dimensional tissue constructs in bioreactors. It ranges from analysis of gene expression to see which signals trigger cell differentiation, to the use of biodegradable polymers as artificial and temporary "scaffolds" for cell growth.
Prof. Sakis Mantalaris
Programme Co-ordinator
