As introduced in Topic 1 the tools of modern molecular biology have led to an explosion in the number and range of biocatalysts available for use. Bespoke recombinant mutant enzymes for organic synthesis can now be rapidly developed and biocatalysis is now an underpinning part of the green chemistry tool box to enable safe and low environmental impact synthesis. Many classes of enzyme of interest to the synthetic organic chemist are now available commercially. Biocatalysis can provide unique catalytic opportunities not accessible with conventional chemistry and can also facilitate efficient shorter routes to complex chiral intermediates.
Whilst biocatalysts may offer various advantages over conventional routes, one should also be aware that significant lifecycle burdens are often generated during the downstream processes for bio-reactions.  The product streams from bio-reactions are typically dilute aqueous solutions, which can bring specific problems that need to be addressed from both an environmental and process optimisation standpoint. For example large amounts of organic solvents may be used for extraction.  All new methodologies developed should be assessed from a holistic perspective, in order to ensure that potential environmental ‘hotspots’ are not missed downstream from the actual synthetic step: see Topic 2: Metrics for further study on holistic assessment of methodologies.
By the end of this module you should: