Rapid Aqueous Synthesis of Mesoporous Carbon and Their HRP Immobilization Performance

Abstract

Mesoporous carbons have been rapidly synthesized by an aqueous way using polymerization of phloroglucinol and formaldehyde in the presence of triblock copolymer F127 (PEO106PPO70PEO106) under different conditions of hydrochlo- ric acid. The micromorphology, pore structure of the obtained materials were characterized in detail by TEM, SEM and N2 adsorption-desorption. The obtained mesoporous carbons were utilized to adsorb the horseradish peroxidase (HRP) and the thermal stability, pH stability and storage stability of the immobilized HRP activity were also investigated. The results reveal the as-synthesized mesoporous carbon has a wormhole-like mesopore structure. The concentration of hydrochloric acid is a key factor influencing the polymerization rate of phenolic resins. With the concentrations of hydrochloric acid increasing from 0.5 mol/L to 2.5 mol/L, the pore size of mesoporous carbons decreased from 7.6 nm to 5.6 nm, the BET surface areas decreased from 787.8 m 2 /g to 691.1 m 2 /g, and pore volumes decreased from 0.64 cm 3 /g to 0.49 cm 3 /g. During the process of polymerization, the phase separation appeared in 20 min, while in the reported work, the polymerization of resorcinol and phenol with formaldehyde took much longer time. After incubation at 70 ℃ for 30 min, the activity of immobilized HRP decreased slowly than that of the free HRP. The free and immobilized HRP remained 12.33% and 56.22% of their initial activity, respectively. Compare to free HRP, the immobilized HRP exhibited higher retention activity with a wider pH range between 4.0 and 10.0. The activity of immobilized HRP was also tested for both operation and storage stability. The enzyme activity of immobilized HRP decreased with increasing amount of recycle times. After recycled for 10 d, the activity of im- mobilized HRP retains 29% of its initial activity. The activity of immobilized enzyme could retain as high as 62% of its ini- tial activity after 50 d of storage at 4 ℃, while the free HRP only retains 31%. The results have shown that the thermal sta- bility, pH stability and storage stability of immobilized enzyme were significantly improved in comparison with free HRP. Keywords rapid aqueous synthesis; mesoporous carbon; horseradish peroxidase; immobilization