Biocatalysis is an exciting, emerging technique for manufacturing APIs. Not only is it green, but it also fills in some of the gaps presented by other catalytic processes, given that it allows new transformations and routes that would not be possible with traditional techniques. Johnson Matthey has been working with catalysts for many years, so we understand the science well. Today, our portfolio of biocatalysts, advanced computational techniques for enzyme development and expertise in reaction engineering, optimization and scale up are making biocatalysis a true complementary solution for most given transformations.
It’s a hit
Finding a good “hit” comes down to sampling and screening a diverse collection of enzyme sequences covering a large portion of a given enzyme family. There is no shortage of effective enzymes that can be used for biocatalysis, but finding the right enzyme for the job, within reasonable timelines and limited resource expenditure, remains a challenge – or perhaps it’s more appropriate to say that it’s a “numbers game,” with millions of potential combinations to investigate. We obtain our enzymes from a variety of sources, including natural enzymes from the public databases, newly discovered enzymes through metagenomic approaches and enzyme engineering. If you have a large portfolio of enzymes, known to catalyze a broad variety of different substrates, you clearly increase your chances of finding an effective hit. In short, you need the enzymes and the ability to test them rapidly – and we have both at Johnson Matthey.But finding the hit is just the beginning because it will be based on a very small-scale reaction under diluted conditions, typically a long way off a solution that can be used industrially. However, it is still possible to improve the process. You need to be an expert on reaction engineering and you need to understand how to modify the set ups to achieve the full potential of the catalyst. The first task is to find out where the limitation lies: is it the catalyst or the process? Generally, we find that, when you move to very concentrated conditions, the enzyme will be limited in terms of its stability (thermo or organic stability, for example). The rate of the enzyme itself could also be inhibited in high substrate loadings. Such limitations can be overcome with reaction engineering, but you can also use enzyme engineering. This is only becoming more popular as our understanding of enzyme structure-function relationships grow, together with the tools to build rational design libraries. We use highly advanced computational techniques that enable us to study the 3D model of each enzyme and rationally select specific regions of the sequence that require fine tuning through mutagenesis. Through these in silico approaches, we can usually identify a suitable mutant within two months. For enzyme engineering to be streamlined, however, you need to have a clear goal in mind and this involves in-depth discussions with our clients.
The natural way
Where possible, we try to develop biocatalysts that do not require enzyme engineering at all – it is possible, and tends to be faster and cheaper. If you screen a large and diverse enough sampling of enzymes – and our collections are large enough to do this – you may find that some are promising enough to work at an industrial level without the need for enzyme engineering. Additional enzyme engineering may not be suitable for every client depending on their timelines and available resources – and if something exists in nature then why not use it? It’s very important to communicate and collaborate with clients to develop the best solution. Sometimes clients come to us and say they need enzyme engineering, but, based on our in-depth knowledge, we may be able to offer another solution that could work better for them. When building our portfolio, we have focused on creating a broad toolbox of potential solutions. Newly discovered enzymes are continually being added to our portfolio as new research is performed. One area of interest is in the synthesis of chiral amines due to their commonality in pharmaceuticals. Traditionally, chiral amines are developed using transaminases, which is offered by many biocatalysis companies. We are also looking at other enzymes classes that will allow for the transformation of pro-chiral ketones to chiral amines: amine dehydrogenases and imine reductases. Both are attracting considerable attention in the research community because of their efficiencies as biocatalysts. Beatriz Domínguez is R&D Manager and Ahir Pushpanath is Team Leader, Biocatalysis, both at Johnson Matthey, UK.
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