High expression and biosilica encapsulation of alkaline-active carbonic anhydrase for CO2 sequestration system development

Abstract

Carbonic anhydrase (CA) is a biocatalyst for CO2 sequestration because of its distinctive ability to accelerate CO2 hydration. High production and efficient immobilization of alkaline-active CAs are required, because one potential application of CA is its use in the alkaline solvent-based CO2 absorption/desorption process. Here, we designed and applied an alpha-type CA from Hahella chejuensis (HCA), which was reported as highly active in alkaline conditions, but was mostly expressed as insoluble forms. We found that the signal peptide-removed form of RCA [HCA(SP-)] was successfully expressed in the soluble form [similar to 70 mg of purified HCA(SP-) per L of culture]. HCA(SP-) also displayed high pH stability in alkaline conditions, with maximal activity at pH 10; at this pH, similar to 90% activity was maintained for 2 h. Then, we prepared HCA(SP-)-encapsulated silica particles [HCA(SP-@)silica] via a spermine-mediated bio-inspired silicification method. HCA(SP-)@silica exhibited high-loading and highly stable CA activity. In addition, HCA(SP-)@silica retained more than 90% of the CA activity even after 10 cycles of use in mild conditions, and 80% in pH 10 conditions. These results will be useful for the development of practical CO2 sequestration processes employing CA. (C) 2015 Elsevier Ltd. All rights reserved.