Carbon composite beads for immobilization of carbonic anhydrase

Fixation of anthropogenic CO2 into calcium carbonate using carbonic anhydrase (CA) as a bio-catalyst appears to be a promising option of CO2 sequestration. In the present study, carbonic anhydrase (CA) has been immobilized on chitosan based activated alumina–carbon composite beads. Synthesized adsorbent was thoroughly characterized using XRD, FTIR, SEM and BET-SA. Maximum adsorption capacities were determined using Langmuir model and it was observed to be 172.41 mg/g. Mechanistic and kinetic aspects have been addressed for immobilized as well as free enzyme. The Km and Vmax for immobilized enzyme was 10.35 mM and 0.99 μmol/ml/min, whereas for free enzyme it was 1.89 mM and 0.99 μmol/ml/min respectively. Proof of concept has been established for carbonation reaction. The carbonate has been characterized using various tools such as XRD and SEM which confirms the calcite nature of calcium carbonate. The CO2 sequestration capacity in terms of conversion of CO2 to carbonate was quantified by gas chromatography (GC). The CO2 sequestration capacity of immobilized beads was found to be 19.22 mg of CaCO3/mg of enzyme as compared to 33.06 mg of CaCO3/mg of enzyme for free enzyme.

(A) SEM image of carbon composite beads and (B) formation of calcium carbonate precipitate by immobilized enzyme.Figure optionsDownload as PowerPoint slideHighlights
► New low cost nitrogen containing biogenic carbon composite has been synthesized from chitosan.
► Partially purified carbonic anhydrase was immobilized on carbon composite beads for sequestration of CO2.
► Proof of concept has been established for carbonation reaction and the CO2 sequestration capacity of immobilized beads was found to be 19.22 mg of CaCO3/mg of enzyme as compared to 33.06 mg of CaCO3/mg of enzyme for free enzyme.