Thermal Biosensors Bioactivity Bioaffinity

Book excerpt: The immobilized biocatalyst (IMB) is a key component of biotransformation systems that are used to transform substrates to desired products. The impro- ment of biocatalyst properties has a direct influence on the overall effectiveness of the process based on the biotransformation. The basic catalytic characte- stics of biocatalyst that are followed include kinetic properties, pH optima, stability, and inhibition. The investigation of catalytic properties of immobilized enzymes is still a time consuming procedure and is not always simple. In the 1980s, a major effort was made to standardize the rules by which IMB is char- terized. The Working Party of EFB on immobilized biocatalysts has formul- ed principles of individual methods, among them the requirement of kinetic characterization [1]. It was recommended to use a packed-bed reactor, equipped with temperature control and with infinite flow circulation. The system should be equipped with a post-column unit to measure the time-dependence of the product or substrate concentration [2, 3], the most commonly used analytical methods being spectrophotometry, chemiluminiscence, automatic titration, bioluminiscence, chromatography, polarimetry, and biosensors based on the oxygen electrode. There are two main drawbacks to the application of these methods: 1. The need to vary the analytical principles, depending on the chemical and physical-chemical properties of analytes; 2. In some cases, mainly in the study of hydrolytic enzymes, the natural s- strate must be replaced by an artificial one, that is chromolytic, chromogenic, chemiluminiscent, bioluminiscent, or fluorescent.