Also engineering the reaction media can contribute to biocatalyst stabilization. This is a key factor for using enzymes in organic synthesis where non-aqueous media are mandatory or at least highly desirable. Bioreactor design requires sound expressions to describe biocatalyst inactivation under operation conditions. Unfortunately, most information has been gathered in non-reactive situations, which poorly describe actual behavior. Models are proposed to consider the presence of substrate and products on biocatalyst stability and thus describe properly bioreactor performance.
Biocatalysts are strictu sensu the catalysts of cell metabolism, i.e. the enzymes.
However, this concept has expanded beyond its physiological meaning, a biocatalyst being, in broader terms, any biological entity capable of catalyzing the conversion of a substrate into a product. In the context of this article, biocatalysts will refer to enzymes isolated from or conditioned within the cell system that produces them. Living cells, as biocatalysts, are beyond its scope. Biocatalysts have competed and will compete with conventional chemical catalysts. Drawbacks are inherent to their complex molecular structure that makes them costly to produce and also intrinsically unstable.