Biocatalytic Membrane Reactors for Sustainable Fine Chemical Production

Fine chemicals are produced in limited volumes at relatively high prices with an estimated global production value of about $85 billion annually. The application of membranes to purify, isolate and recycle the reagents, products and catalysts has gained increasing attention for the sustainable synthesis of high-value fine chemicals such as (bio)pharmaceuticals. In the last decades, a plethora of materials and processes have been developed to synergistically combine membranes and catalysis in organic media, covering various disciplines from microfluidics to enzymes. Enzymes are proteins that increase the rate of chemical reactions. They are regio-, enantio- and stereoselective, can carry out reactions with a high atom efficiency, work at lower operating temperatures than conventional organic transformations, and create less solvent waste. Therefore, they are being integrated into industrial processes for the production of high-value chemicals. Almost all of these enzymatic reactions are carried out in batch rather than continuous processes. This leads to time-consuming separation and recovery steps. Also, many enzymatic transformations are product inhibited, leading to diminishing returns during processing. Nanoporous membranes have pores the size of small molecules. These pores allow for the continuous purging of the product and simultaneous quantitative recovery of the valuable biocatalyst without the need to stop the reaction and reactivate the catalytic system. The rate of product recovery can be balanced with the rate of reactant addition to maximise the efficiency of the process and minimise product inhibition.

The project will begin with training in protein handling, biochemical assays, membrane production, liquid-phase separations, and characterisation methods such as liquid chromatography and electron microscopy. The student will initially source enzyme commercially and screen them for catalytic activity under non-aqueous conditions. Organic solvents have been selected as reaction media due to the high solubility of the pharmaceutical substrates, increased stability and kinetic performance of certain biocatalysts. Initial studies will focus on homogeneous systems. A longer-term objective is to create a hybrid system in which the enzymes are immobilised on the surface of the nanofiltration membrane to create an 'all-in-one' component for continuous chemical processing. The viability of the resulting enzymatic membrane reactor will be evaluated through a pharmaceutical case study. Green metrics and techno-economic analysis will be performed to assess the overall sustainability of the hybrid system.