Evaluation of the operational conditions of the glucose oxidase and catalase multienzymatic system through enzyme co-immobilization on amino hierarchical porous silica

Hexaric acids have attracted attention lately because they are platform chemicals for synthesizing pharmaceuticals. In particular, gluconic acid is one of the most studied because it is readily available in nature. In this work, operational conditions like temperature and pH were evaluated for the enzymatic production of gluconic acid. For this purpose, glucose oxidase (GOx) and catalase (CAT) were individually immobilized and co-immobilized using amino-silica as support. The catalytic performance of the enzymes both as separate biocatalysts (GOx or CAT) and as an enzymatic complex (GOx-CAT) was assessed in terms of enzymatic activity and stability at temperatures 45 °C and 50 °C and pH 6 to 8. The results show that CAT is a key enzyme for gluconic acid production as it prevents GOx from being inhibited by H2O2. However, CAT was found to be less stable than GOx. Therefore, different GOx to CAT enzymatic ratios were studied, and a ratio of 1–3 was determined to be the best. The highest glucose conversion conditions were 45 °C and pH 7.0 for 24 h. Regarding the biocatalyst reuse, GOx-CAT retained more than 70% of its activity after 6 reaction cycles. These results contribute to further knowledge and application of oxidases for hexaric acid production and shed greater light on the role of the glucose oxidase/catalase pair in better catalytic performance. Both enzymes were immobilized in one pot, which is relevant for their potential use in industry; an enzyme system was obtained in a single step.