Efficient control of dissolved and colloidal substances in raw papermaking whitewater by immobilized thermophilic esterase from a metagenomic library

This study aimed to investigate the versatility of thermophilic esterase for treating raw papermaking whitewater with organic solvents at high temperatures. Thermophilic esterase from a metagenomic library was immobilized on a chitosan/macroporous resin composite carrier using a covalent crosslinking approach in conjunction with deep eutectic solvent (DES). The stability and tolerance of the immobilized thermophilic esterase were greatly enhanced by DES. Immobilized thermophilic esterase resulted in significant 85.35% and 88.02% reductions in the average particle size and pitch deposit contents, respectively. Furthermore, clear decreases in turbidity, chemical oxygen demand and biochemical oxygen demand were found, indicating an optimal treatment outcome for all the commercial enzymes that were examined. The superior efficacy of thermophilic esterase in the treatment of raw whitewater was found to be due to the effective removal of colloidal substances such as polyvinyl acetate. Therefore, this research had significant potential for the enzymatic treatment of raw whitewater.