Design-of-experiment strategy for the formulation of laccase biocatalysts and their application to degrade bisphenol A.

Immobilizing enzymes can expand their applicability to continuous process operations and facilitates process intensification. An optimized formulation of immobilized biocatalysts is therefore of strategic interest in the field of industrial biotechnology. Nevertheless, biocatalyst formulation still largely relies on empirical approaches which lack effectiveness in the identification of optimum immobilization conditions. In the present study, design of experiments, multiple linear regressions and modeling were used to screen, interpret and finally optimize crucial immobilization parameters. A laccase preparation from Coriolopsis polyzona MUCL38443 was immobilized via a sequential adsorption-crosslinking process on mesoporous silica particles. As a target variable, biocatalyst activity was doubled (∼280 U g(-1)) while dramatically reducing processing time (two hours instead of 26 hours) and reagent inputs (80 mm instead of 1m glutaraldehyde (GLU)). Immobilization yield (∼50%) and thermostability (∼60% residual activity after 24 hours at 45°C) could be maintained under the optimized conditions. As an example of its application in environmental biotechnology, the optimized biocatalyst was implemented in a continuous stirred-tank membrane reactor (CSTMR) to continuously degrade the endocrine disruptor bisphenol A (BPA) in wastewater. A 90% removal of 50 μm BPA was achieved over 30 reactor volumes (hydraulic residence time (HRT) of 1.85 hours, 50 mL working volume).