What are they?
Flexible whole cell biosensor is an appealing field. Whole-cells are a natural factory of biocatalysts. Usually, the method for acquiring isolated biocatalysts, like the enzymes, requires a process of separation and purification from the raw whole-cell strain or tissue, which is tedious, time and resource consuming. Furthermore, added advantage of whole cell biosensor over enzyme biosensor are that the enzyme sometimes requires cofactors and coenzymes, to carry out a complete reaction or to recognize a substrate, which implies a recycling process to attain the required cofactor, then the need for further separation and purification steps. Whole-cells contain a complete metabolic aggregate of enzymes, cofactors and coenzymes. Analog processes can be found in tissues. The requirements related to maintenance and cost for culturing microorganisms are below from those of tissue cultures.