| Biocatalysis-the use of enzymes to catalyze a | | | | fewer side reactions, elimination of protection and |
| chemical reaction-has become a scientific buzz word. | | | | de-protection steps, purer products, easier recovery |
| To be clear, a biocatalyst can be one or more | | | | and separation, and reduced environmental waste. |
| enzymes or cells-living, dormant, or dead-and the | | | | There are also operational advantages, including the |
| reaction can be a single chemical reaction or series of | | | | ability to carry out reactions under mild operational |
| reactions. Thus, biocatalysis includes the one-step | | | | conditions, avoiding extremes of pH, temperature, |
| enzymatic production of aspartic acid (a component | | | | and pressure that often require the use of expensive |
| of the non-caloric sweetener aspartame), the | | | | equipment or energy intensive processing. Biocatalytic |
| two-step oxidation of ethanol to acetic acid (vinegar | | | | processes also rely on catalysts that are |
| can be made this way, and if it is, it is called natural), | | | | biodegradable and are produced from renewable |
| and the multi-step brewing of beer (quite likely the | | | | resources, meaning the processes are typically |
| oldest example of biocatalysis, with historical records | | | | "greener" and more sustainable. Since there is an |
| dating back 6000 years!). Proponents say biocatalysis | | | | enzymatic counterpart to most known chemical |
| is green and sustainable. Critics will tell you that it is | | | | reactions, the potential scope for the application of |
| often costly and requires a development timeline that | | | | biocatalysis is broad. |
| is too long to meet the needs of real world industrial | | | | Practically speaking, however, this breadth of scope |
| manufacturing. What is the reality? | | | | in the chemical industry has not been realized. |
| At the outset it is important to point out that | | | | Presently, I estimate that well over 100 different |
| biocatalysis is not a panacea, and never will be, and I | | | | biocatalytic processes are implemented in |
| say this as an evangelist for biocatalysis. There are | | | | pharmaceutical, chemical, agricultural, and food |
| both pros and cons for the use of biocatalysis as | | | | industries, which may at first glance seem |
| compared to more traditional chemical catalysis. As a | | | | considerable. However, this represents only a small |
| catalyst, a biocatalyst does what any catalyst can do: | | | | fraction of the processes developed and carried out |
| increases the rate at which a chemical reaction takes | | | | currently. Enzymes have not yet been developed to |
| place, but does not affect the thermodynamics of | | | | cover as broad a spectrum of chemical reactions as |
| the reaction. To take maximum advantage of | | | | have chemo-catalysts. Researchers in both academia |
| biocatalysis, we need to understand what | | | | and companies are working to overcome this |
| biocatalysts do well, and equally what they do poorly, | | | | limitation, but it will take time. |
| and then seek to implement biocatalysts in processes | | | | Speed of process development is also often slower |
| that benefit from their advantages. | | | | for biocatalytic processes than their chemical |
| One of the most important advantages of | | | | counterparts, in part due to the lack of experience |
| biocatalysts is high selectivity, manifested as | | | | that chemists have with the use of enzymes and |
| stereo-selectivity (for chiral synthesis or separation, | | | | microbial cells. Modern biotechnological tools now allow |
| often used for the synthesis of pharmaceutical | | | | enzymes to be significantly improved-optimized-for a |
| intermediates in which only one stereoisomer | | | | desired reaction, but this optimization is often too |
| possesses the desired biological activity), positional | | | | costly and time-consuming to meet tight timelines; |
| selectivity (also known as regio-selectivity, allowing | | | | therefore, broad application remains elusive. By |
| selective modification of a specific site in a molecule), | | | | focusing now on those reactions where enzymatic |
| and functional group selectivity (i.e. chemo-selectivity, | | | | alternatives are already well-developed, honing our |
| allowing one type of chemical functional group to be | | | | expertise in using biocatalysis, and staying abreast of |
| modified in the presence of another, sometimes | | | | future developments that will bring a wider range of |
| more reactive functional group). | | | | practical biocatalytic alternatives, we can choose |
| Such selectivity is highly desirable in chemical | | | | wisely where to invest resources to maximize the |
| synthesis, offering benefits such as higher yields, | | | | value of this rapidly developing technology. |