Enzymes immobilized in wood-derived cellulose scaffold for constructing a novel modular bioreactor

Modular bioreactors can provide a flexible platform for constructing complex multi-step pathways, which may be a solution for maximizing reactions and overcoming the complexity of multi-enzyme systems. Here, we selected wood-derived cellulose scaffold as a support for enzyme immobilization and constructed the modular bioreactor. Cellulose scaffold was prepared after removing lignin from wood, followed by citric acid functionalization and the addition of glutaraldehyde finally allowed the cross-linking of enzymes. Three enzymes, horseradish peroxidase (HRP), glucose oxidase (GOD), and catalase (CAT), were separately immobilized, resulting in the immobilized enzyme amount to over 40 mg/g. The introduction of carboxyl groups from citric acid facilitated the rapid enzyme adsorption on the support surface and immobilized enzymes possess ∼65% expressed activity. Modular bioreactors were constructed by using the immobilized enzymes. With the immobilized HRP module, reactor showed desired catalytic performance with the phenol degradation rate of > 90%. Also, a pH regulation can occur in the bioreactors for preserving enzyme activities and neutralizing acid products. In the GOD/CAT modular bioreactor, the cascade reaction with adjusting pH values can achieve a 95% yield of sodium gluconate and exhibit a favorable reusability of 5 operation cycles.