There are many industrial applications of biocatalysis such as esterification and amide formation that involve water as a by-product and also as a necessity to sustain enzymatic activity.
A good example for this is the enzymatic production of Capsaicin. The increasing concentration of water promotes the reverse reaction (hydrolysis), limiting yields and reaction rates.
In short: both, hence it is a powerful parameter for reaction optimization. Research from Lund University showed that the effect of water activity on an enzymatic transesterification was two-sided: "Water is needed initially to start the reaction and maintain enzyme activity but has a negative effect on both the yield and product quality towards the end of the reaction." Find the article here.
Challenges presented by water as a by-product can be overcome through continuous water removal. This maintains a thermodynamic equilibrium favourable for product formation. A common strategy to do so is evaporation, in which the water is cleared from the reaction mixture via the headspace. Hereby, a combination of heating and vacuum accelerates the process and allows for evaporation at temperatures much milder than 100 °C. For purposes like this, SpinChem's reactors are suited for connection to vacuum systems.
Another approach for water removal is provided by molecular sieves. These are solid materials made from minerals with well-defined pore sizes that strongly bind water. The water is thereby removed from the bulk reaction phase and stored in the solid desiccant phase, which can absorb up to 15% of its own weight in water.
As effective as they are, molecular sieves are also brittle. Propeller blades and magnetic stirring bars will chip away at the particles, producing fines that are hard to remove. When using a rotating bed reactor, the material is protected from mechanical forces, preventing its breakdown. See a comparison of used molecular sieves in either a standard stirred tank reactor and a rotating bed reactor (RBR) below.The RBR simplifies downstream processing and makes solids such as molecular sieves feasible in applications they would otherwise contaminate.
Do you have a biocatalytic application that can be improved?
Use a rotating bed reactor to screen for optimal reaction conditions, then use the same technology to manufacture on industrial scale. Ask us how!
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