Effect of synthesis conditions on physical properties, laccase catalytic activity and stability of sol-gel laccase

Abstract

The physical properties, laccase catalytic activity and stability of sol–gel laccases prepared at various synthesis conditions were investigated. The sol–gel laccases were characterized using the scanning electron microscope (SEM), Fourier transform infrared spectrophotometer and nitrogen adsorption/desorption analyzer. The laccase catalytic activity of the synthesized sol–gel laccases was determined by using 2,6-dimethoxyphenol as a standard substrate. The SEM results confirmed that the sol–gel laccases have a spherical agglomerated particle morphology having surface area and pore properties varied with synthesis conditions. It was found that the laccase catalytic activity and stability of sol–gel laccases were enhanced depending on synthesis conditions used. There was no significant laccase leaching observed, suggesting that most of the laccase molecules were sterically confined in the silica matrices. The highest laccase catalytic activity was observed for the SOLAC04 (480 AU) which also had the highest surface area (445 m2/g), pore size (30.7 nm) and pore volume (1.14 cm3/g). The optimal conditions for the laccase loading were 10 mg/mL, pH for both free laccase and SOLAC04 was 6, and temperature for the free laccase and SOLAC04 was 50 and 40 °C, respectively. The laccase catalytic activity of SOLAC04 could retain almost 90 % of its original activity after 34-day storage duration at 27 °C. These results demonstrated the advantages offered by the sol–gel laccases.