Solid/gas biocatalysis

Solid/gas biocatalysis is a technology based on the use of solid biocatalysts for the conversion of gaseous substrates, in the absence of any solvents. Solid biocatalysts are purified freeze-dried enzymes or enzymes present in dehydrated cells. Bioreactors are used in continuous mode, enabling precise control of all thermodynamic parameters influencing reaction kinetics and biocatalyst stability (temperature, pressure and gas flow composition).

From a fundamental point of view, the absence of solvents and the independent control of each substrate's thermodynamic activity (a parameter reflecting its availability to the biocatalyst) are the strong points of this technology. Indeed, it is possible to free ourselves from the effects induced by the solvent, the main species in liquid media, and access the intrinsic parameters of an enzyme. What's more, the ability to independently modulate the thermodynamic activities of each substrate enables us to study the impact of each species present in the biocatalyst microenvironment on its activity, specificity or stability.

From a technological point of view, solid/gas biocatalysis enables very high production yields to be achieved with a reduced plant size. The absence of solvents simplifies purification steps and facilitates product recovery. Catalysis temperatures, although high for enzymatic conversions, remain modest compared with those often used for chemical catalysis. All these features make solid/gas biocatalysis an atom- and energy-efficient, environmentally-friendly process. Nevertheless, the scope of application of this technology is limited compared with that of non-conventional liquid reaction systems, as it is based on the volatile nature of the substrates and reaction products.

Future applications for solid/gas catalysis could include the environmental and pharmaceutical sectors, with a particular focus on the production of chiral synthons.