14 Chapter 2 oxygenases Similarly, many oxygenation reactions (Table 2.1), which also require cofactors, are usually performed using whole micro-organisms. Collectively, oxidoreductases and oxygenases account for around 30% of all reported biotransformations. Enzymes such as lyases, transferases and isomerases(Table 2. 1) account for most of the of industrially applied biotransformations. 2. 3. 1 Enzyme catalysed processes Enzymes isolated from micro-organisms have many desirable properties as catalysts for he synthesis of industrial chemicals, but there are associated problems associated the provision of enzyme cofactors can be expensi most enzyme reactions are carried out in water and the enzymes must be separated from the product stream; the product stream is often very dilute, presenting problems of product preparation of a crude or purified cell-free enzyme preparation is necessary Advances in genetic and chemical enzyme modifications, enzyme immobilisation and immobilisation enzymatic reactions in organic solvents, have increased the actual use and potential of enzymes in the production of industrial chemicals. Enzyme immobilisation, in particular, has proved to be a valuable approach to the use of enzymes in chemical synthesis. The term denotes enzymes that are physically confined or localised in a defined region in with retention of their catalytic activities. a detailed consideration of immobilisation techniques is beyond the scope of this chapter; the subject is covered adequately in the biotol text entitled'Technological Applications of Biocatalyst enzyme Enzyme immobilisation allows the construction of enzyme reactors in which the bioreactor enzyme can be reused. Furthermore, the process operates continuously and can be sign readily controlled Enzyme reactors currently in use include those illustrated in Figure14 Chapter 2 oxygenases associated problems enzyme immobilisation enzyme boreactor design Similarly, many oxygenation reactions (Table Z.l), which also require cofactors, are usually performed using whole micro-organisms. Collectively, oxidoreductases and oxygenases account for around 30% of all reported biotransformations. Enzymes such as lyases, transferases and isomerases (Table 2.1) account for most of the remainder of industrially applied biotransformations. 2.3.1 Enzyme catalysed processes Enzymes isolated from micro-organisms have many desirable properties as catalysts for the synthesis of industrial chemicals, but there are associated problems: their protein structure may not be stable under non physiological conditions which may be detrimental to their long term use, especially at elevated temperatures; the provision of enzyme cofactors can be expensive; 0 most enzyme reactions are carried out in water and the enzymes must be separated from the product stream; the product stream is often very dilute, presenting problems of product concentration and recovery; 0 preparation of a crude or purified cell-free enzyme preparation is necessary. Advances in genetic and chemical enzyme modifications, enzyme immobilisation and enzymatic reactions in organic solvents, have increased the actual use and potential of enzymes in the production of industrial chemicals. Enzyme immobilisation, in particular, has proved to be a valuable approach to the use of enzymes in chemical synthesis. The term denotes enzymes that are physically confined or localised in a defined region in space with retention of their catalytic activities. A detailed consideration of immobilisation techniques is beyond the scope of this chapter; the subject is covered adequately in the BIOTOL text entitled 'Technological Applications of Biocatalysts'. Enzyme immobilisation allows the construction of enzyme reactors in which the enzyme can be reused. Furthermore, the process operates continuously and can be readily controlled. Enzyme reactors currently in use include those illustrated in Figure 2.1