ABSTRACT
Microorganisms can be used as a convenient source of enzymes, since these same proteins provide them with the means to grow on a variety of complex organic compounds. The enzymes can be used in their purified form (either immobilized or in solution) but are sometimes more stable when whole cells are used. Bacterial cells may be rendered nonviable by immobilization or permeabilization but still retain catalytic activity. This can alleviate the need to provide cofactors such as ATP, which can add significantly to costs. The reactions the enzymes catalyze are often regiospecific (attacking a single group on a molecule but leaving others of the same chemical composition) and stereo-specific (attacking one enantiomer such as D-glucose, but not the corresponding stereo-isomer). The specificity of enzymes has allowed industrial chemists to perform reactions that would be impossible by normal synthetic routes, but mostly biotransformations are cheaper to perform and have a higher yield.
