Evaluating the Performance of Different Substrates for Preparing Enzyme-Immobilized Bioreactors

A suitable substrate is needed for enzymatic bioreactors that can provide better stability and reusability for enzyme immobilization. In this work, glass slides and silicone tubing were used as substrates for horseradish peroxidase (HRP) enzyme immobilization. First, the substrates were treated with (3-amino-propyl)-triethoxy-silane (APTES), followed by either dextran polyaldehyde (DPA) or glutar-aldehyde (GA) treatment. Finally, the enzyme was immobilized on the surface of each substrate and used for phenol degradation. It is found that HRP immobilized on glass slides can degrade 21% phenol (1 mg/mL); meanwhile, on silicone bioreactors it can degrade 10% phenol. Moreover, the maximum HRP loading was found to be 6% with 2.52 U total activity on a DPA-treated glass slide, whereas the minimum loading was 3% with 1.26 U total activity on GA-treated silicone tubing. Afterward, the reusability of bioreactors prepared on DPA- and GA-terminated glass slides and silicone tubing was checked for phenol degradation, and it was found that glass slide substrates maintain 100% of the original activity regardless of the chemical treatment; however, silicone tubing loses activity and retains 91.5% of the original activity after 8 cycles of use. Finally, the storage stability of chemically treated (DPA- or GA-terminated surface) glass slides for preparing HRP-immobilized bioreactors was checked over a period of 4 months by using phenol degradation phenomena to find which one(s) can be used as a ready-to-use substrate for enzyme immobilization. It is found that DPA-terminated surfaces can preserve 100% of the original activity, whereas GA-terminated surfaces can hold about 90% of the original activity.