Poly(vinyl chloride) tubing with covalently bound alkaline phosphatase and alternative approach for investigations of open-tubular bioreactors

A one-step carbodiimide method was found to allow covalent binding of enzymes to the inner wall of poly(vinyl chloride) (PVC) tubing. The immobilization is performed under mild conditions without laborious pretreatment or activation of reactor surface. In these preliminary studies, alkaline phosphatase (ALP, EC 3.1.3.1) and p-nitrophenyl phosphate (NPP) were applied as a model enzyme and substrate, respectively. The resulting open-tubular bioreactor exhibits satisfactory operational and storage stability. In addition, a novel and very simple instrumental concept for optical monitoring of the biocatalytic process directly inside the microbioreactor using a system of paired emitter-detector diodes is presented.