3D-Printed interfacial devices for biocatalytic CO₂ conversion at gas-liquid interface

Carbonic anhydrases (CAs) are enzymes that can function at physiologic interfaces and catalyze the interfacial conversion of carbon dioxide (CO₂) into bicarbonate (HCO₃^-) with an extraordinarily high catalytic efficiency. Even though CAs have potential to be used for CO₂ sequestration, significant mass transfer resistance and poor enzyme stability at gas-liquid interface often limit the effectiveness of the enzyme. Here, we report a density-adjustable 3D-printed platform, which can accommodate electrospun polymer fibers with immobilized CA and enable the positioning of immobilized CA in an air-water biphasic system. By using 3D printing, we fabricate interfacial devices consisting of two floating units and different number of biocatalytic units. Two mesh structures of each biocatalytic unit are used to sandwich immobilized CA while two floating units, connected on either side of the biocatalytic units, have an internal hollow volume that enables controlling the position of the enzyme-loaded interfacial device at or near the air-water interface. The positioning of interfacial device directly at the biphasic interface accelerated CO₂ conversion by 1.8- and 3.4-fold when compared to reactions performed with immobilized CA within the aqueous solution and a control interfacial device without immobilized CA, respectively. The CA-loaded interfacial device retained 99.3 % and 88.2 % of its initial CO₂ conversion rate after ten recycles and after subsequent storage in an aqueous buffer at 4 °C for 459 days, respectively. Facile combination of interfacial devices and immobilized enzymes on polymer fibers has paved the way to practical uses of biocatalysts for interfacial CO₂ sequestration.