Recycling the enzyme

It should be briefly mentioned that glycosidases have also been used whilst immobilised on a powdered nylon column [11] and a non-ionic Amberlite resin [31] so that the enzyme can be recycled for several experiments. 

---

The difficult elimination is accomplished by making it an ammonia transfer reaction rather than an elimination of ammonia. Recycling the enzyme does eventually require elimination of ammonia... 

In spite of the low productivity of the enzymic process - the large volumes of solution with low concentration of product the long duration of reaction and the need of additional purification, filtration, and extraction of product from reaction mixture the instability of the enzyme and the impossibility of recycling the enzyme - this process is still used in practice. 

In order to recycle the enzyme, since it is quite expensive, a new method of immobilizing the enzyme was introduced. The HRP was immobihzed on chitosan powder by a simple glutaraldehyde bridge method [49]. The immobilized HRP had the same catalytic function as the enzyme solution. The spectroscopic characterization indicated that the polyanihne obtained by this method was similar to that formed using HRP in solution as a catalyst [50]. 

A final example shows a process called desymmetrization (Figure 15.25). We start with a raeso-compound (remember this is a molecule that contains asymmetric carbon atoms but is not chiral, because it has a plane of symmetry) with two identical functional groups. Under enzymatic hydrolysis, only one of these reacts, so a chiral compound is produced, and all the material is used, without any need to recycle. The enzyme used in this reaction is electric eel acetylcholinesterase (EEAc). Pig liver esterase is also commonly used, as a relatively crude extract is inexpensive and gives good results. An example is shown in Figure 15.26, in the synthesis of 7 -mevalonolactone, important in the biosynthesis of terpenes and steroids. 

---