Synthesis and characterization of thermo-responsive poly(N-isopropylacrylamide)-bovine liver catalase bioconjugate

Thermo-responsive poly(N-isopropylacryalamide) (PNiPAAm) and polyacrylamide (PAAm)-bovine liver catalase bioconjugates were synthesized via copolymerization reaction between acylated catalase and polymeric monomers. The PNiPAAm bioconjugate behaved as a temperature responsive biocatalyst and did show temperature dependent phase transition whereas, polyacrylamide bioconjugate and unmodified catalase did not show such property. The synthesized PNiPAAm-catalase and PAAm-catalase bioconjugates have weight average molecular weight (Mw) of around 140 kDa and 143 kDa with polydispersity index (PDI) of 1.02 and 1.43, respectively. The pH and temperature optimum range of catalase became broader after conjugation with polymers and lower critical solution temperature (LCST) of PNiPAAm decreased to 26 °C from 32 °C. The PNiPAAm-catalase showed better thermal stability than polyacrylamide conjugated and native catalase under isothermal heating at 55 °C as well as heating at different temperatures (10–80 °C). Moreover, PNiPAAm-catalase bioconjugate showed better operational stability than PAAm conjugated and native catalase up to 20 precipitation–redissolution cycles. Additionally, storage stability of PNiPAAm-catalase has also been shown to be better than other preparations up to 20 days of storage.