18: Enzymes for Biocatalysis: Key Concepts, Engineering Principles and Case Studies

Enzymes are Nature’s remarkable catalysts found in every living organism. They are capable of catalysing a diverse range of chemical reactions being exquisitely selective, providing fast substrate conversion, water solubility, low operation temperature, and generating few by-products. All this makes enzymes an attractive, environmentally friendly alternative to conventional chemical catalysts. Consequently, the last two decades have seen continuously increasing applications of these ‘biocatalysts’ in a number of different industries. However, the use of enzymes generates some challenges such as their susceptibility to substrate and product inhibition, low stability in operating processes (high temperatures, non-neutral pHs), low solubility in organic solvents and low activity with unnatural substrates or enantiomers. A combination of advances in molecular biology, the availability of an increasing number of gene/genome sequences and high resolution enzyme structures has allowed the engineering of tailor-made enzymes able to meet the requirements of industrial processes. This chapter reviews the traditional and newer state-of-the-art techniques to engineer and evolve biocatalysts.