Structural regulation by calcium ion in preparing cross-linked enzyme aggregates

Abstract:

We studied the effect of calcium ion on particle size and pore structure of cross-linked enzyme aggregates (CLEAs) of glucose oxidase, with activity and stability of the enzyme as evaluation criteria. With calcium ion to prepare CLEA significantly decreased particle sizes of CLEAs whilst the pore structures of CLEAs gradually disappeared with the increase of calcium concentration. When glucose oxidase was precipitated at 0.1 mmol/L Ca2+, glucose oxidase in CLEA showed the definitive pore structure. Moreover, glucose oxidase activity in CLEA with Ca2+ was 1.69 times higher than that without Ca2+. Even at Ca2+ as high as 1.0 mmol/L, glucose oxidase activity in CLEA was 42% higher than that of CLEA without Ca2+. Furthermore, CLEA prepared with 0.1 mmol/L Ca2+ not only exhibited higher substrate conversion and operational stability, but also increased the maximum reaction speed. Therefore, calcium ion improved the performance of glucose oxidase in CLEAs.