Membrane bioreactors are reactors in which membranes have been incorporated to synergistically perform multiple functions to enhance the overall process being performed. They are used in the pharmaceutical and biotechnology industries for Process Intensification. In particular, membrane bioreactors are applied extensively for the manufacture of biological products using enzyme reactions, and are common in the pharmaceutical/biomedical industry. They enhance the sustainability of a process by replacing more energy-intensive techniques such as distillation and evaporation. The are also operationally much simpler, and can be made to be highly selective to the specific desired process.
Membranes can play a number of different roles in enzymatic reaction processes. They might serve as catalysts or act as an osmotic/filtration separation material. Biological membranes play many important roles in living organisms, acting as barriers that control transport of molecules and nutrients in and out of cells, while also regulating electrochemical signals within the cell and other signals between cells. According to Drioli and Curcio (2007) their thermodynamic efficiency can exceed that of the internal combustion engine by over 100%. There is much room for discovery in membrane reactor technology. For example, it has been shown that physicochemical and structural properties (i.e. thickness, pore size and porosity) of membranes used to provide a surface for protein crystallization (to study the structure of a purified protein), can be manipulated in many ways to alter the kinetics of nucleation and, thus, the rate of formation of the crystal.
Types of conventional membrane operations are:
- Microfiltration (MF)
- Ultrafiltration (UF)
- Nanofiltration (NF)
- Reverse osmosis (RO)
- Pervaporation (PV)
- Membrane emulsification
Drioli, E. and Curcio, E. 2007. Membrane engineering for process intensification: A perspective. J. Chem. Technol. Biotechnol. 82:223-227.
Curcio et al. 2006. Influence of the structural properties of poly(vinylidene fluoride) membranes on the heterogeneous nucleation rate of protein crystals. J. Phys. Chem. B. 110:12438-12445.