Engineering of thermometric biosensors and characterisation of redox enzymes for improved performance of biosensors/biofuel cells

The present work is mainly focused on the development of enzyme-based bioanalytical devices, which can further be applied as analytical tools for industrial, medical and environmental applications. The first part of the work deals with the practical applications of thermometric biosensors for determination of various sugars (fructose and lactose) in a real samples. Thermometric biosensors possess properties, which make them appealing compared with for instance the widely utilised amperometric biosensors for application in certain areas as discussed in a review. Demonstration of the capabilities of a ‘hybrid’ biosensor technology combining the advantages of two different detection principles is also discussed. Another direction of the work in focused on a comprehensive characterisation of a promising redox enzyme – pyranose dehydrogenase (PDH) for further application in the development of amperometric biosensors and fabrication of bioanodes. The electrocatalytical performance of the enzyme is studied using two different electron transfer mechanisms: i.e., mediated electron transfer, by wiring PDH with osmium-bound redox polymers on the surface of a graphite electrode, and direct electron transfer, by direct adsorption of the enzyme on the surface of a graphite electrode. The current density response obtained from oxidation of various sugars by PDH, is measured using electrochemical techniques, such as flow-injection amperometry and cyclic voltammetry. The work is aimed at improving the current output by downsizing the enzyme’s dimensions through depletion of the glycosylation, additional fragmentation and recombinant production of the mutant enzyme possessing a different degree of glycosylation