Enzyme-PEI-clay composites for chemical and biological remediation of formaldehyde

Formaldehyde (FA) is an organic chemical used in many industries. It is toxic and has been listed as a probable carcinogen. Although FA remediation technologies have advanced over the years, significant problems still hinder efficient remediation. Herein, we propose a one-step solution that combines chemical adsorption and biological degradation in order to improve on the separate systems and overcome the major pitfalls of each. The proposed biomaterial rapidly yet reversibly adsorbs FA which is then degraded by co-localized enzymes. The immobilization protects the biological components from detrimental conditions allowing efficient remediation and enabling continuous use. The biomaterial is based on FA-degrading enzymes immobilized with polyethyleneimine (PEI) on montmorillonite clay. The PEI was chosen because it is known to both protect enzyme activity at the immobilized state and can adsorb high concentrations of FA. Two enzymes were chosen to fully degrade FA; Formaldehyde dismutase that transforms FA to formic acid and Formate dehydrogenase that breaks down the formic acid to CO₂ and water. The enzyme combination also regenerates the co-factor (NADH/NAD+) allowing continuous low-cost use. To best prepare the materials, enzyme engineering and enzyme immobilization are being studied in parallel. Formaldehyde dismutase was cloned into E. coliBL21 for overexpression and expressed with molecular chaperones to produce a soluble active enzyme. Meanwhile, a model enzyme, Aldehyde dehydrogenase, was coated with a range of MW-PEI polymers to optimize enzyme activity at high FA concentrations and then immobilized on clay. Finally, the engineered enzymes will be implemented in the immobilized system to create FA-degrading bio-clays. Such bio-clays could efficiently remove and degrade FA from concentrated effluent, polluted indoor air and commercial products in a continuous manner.