Biotransformation by isolated enzymes
Isolated enzymes typically have higher biotransformation rates than cell culture-based methods. But the cost of isolating the enzyme plays an important role in using that enzyme to produce volatiles [144]. Enzymes have a high selectivity and minimize the production of undesirable by-products [145]. However, most studies have been done by whole-cells systems rather than isolated enzymes (7%) [146]. Although this method has been significant extent [147], but only in cases of biological transmission, volatiles are present. The use of isolated enzymes for biotransformation depends on the availability of the enzyme for the desired conversion reaction, pH, optimum temperature conditions, solvent and substrate. The nature of the enzyme, the type of biotransformation reaction and the need for a cofactor are the determining factors of the method of using the enzyme. In order to facilitate the separation of the product and the catalyst recycling, the use of immobilizing the enzyme is preferred [148].
The table 7 and 8 present a list of some of the volatile compounds produced by biotransformation of plant cultures, microorganisms and isolated enzymes.