The use of affinity polypeptides, also called tags, is a common technology both in basic research and industrial processes. We have developed two advantageous systems to purify and immobilize fusion proteins in solid supports using two types of tags: 1) The ChBD, which recognizes choline and other analog compounds, allows the purification of fusion proteins in one step, by DEAE-cellulose chromatography. We have successfully purified the DAO-ChBD, with D-amino acid oxidase activity and ChBD-Pyr, with pyrophosphatase activity. 2) BioF, a new tag to obtain fusion proteins immobilized to medium chain length polyhydroxyalkanoates, a biodegradable and biocompatible solid support. We have prepared a biotechnological product, Pfk-Bt1, based on the immobilization of a Bacillus thuringiensis toxin to biodegradable bioplastics. This project is being developed in collaboration with the group of Environmental Biotechnology.