Characterization of technical grade carbonic anhydrase as biocatalyst for CO₂ capture in potassium carbonate solutions

Abstract

Reactive absorption promoted by carbonic anhydrase (CA, E.C. 4.2.1.1.) catalysis has been proposed for CO2 capture from exhaust gas as an alternative to the reactive absorption in amine solutions. Potassium carbonate solutions allow feasible CO2 capture assisted by CA. This paper reports on the characterization of a CA form supplied by Novozymes as a catalyst for CO2 capture in K2CO3 solutions at operating conditions relevant for industrial processes (2–3 M K2CO3, 298–313 K, 0–40% carbonate to bicarbonate conversion). CO2 absorption tests were carried out in a batch‐stirred cell apparatus at constant gas volume and temperature by measuring gas pressure decay. The enhancement ratio between CO2 absorption rate with and without the enzyme at biocatalyst concentration above 0.3 kg m−3 ranged between 5 and 8 depending on the solvent composition and temperature. Active enzyme aggregates formed at protein concentration larger than 0.3 kg/m3 and their contribution to the absorption rate enhancement was remarkable. Assessment of enzyme kinetics in homogeneous solutions at enzyme concentration lower than 0.018 kg·m−3 showed that kcat/KM increased with both temperature and salt concentration. kcat/KM ranged between 9.0·103 and 7.0·104 m3·kg−1·s−1 in agreement with literature data on carbonic anhydrase kinetics. Reliability of the adopted method for kinetic characterization was confirmed. The activity of enzyme aggregates formed in the carbonate solvent was verified and CA aggregates can be used to select the proper CA based biocatalyst for CO2 capture application as an alternative to free and immobilized enzyme. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.

Rapid and Positive Effect of Bicarbonate Addition on Growth and Photosynthetic Efficiency of the Green Microalgae Chlorella Sorokiniana (Chlorophyta, Trebouxiophyceae)

“…Among these, recent studies on the effects of bicarbonate in microalgae cultivation aimed to improve biomass production or content of functional molecules [23,26,28,29]. The bicarbonate salt, as an extra source of inorganic carbon for microalgal cultures, has been proposed due to the possibility of being produced by hydration of CO 2 present in polluting fumes, reducing CO 2 emissions into the atmosphere, besides economic advantages [27,[54][55][56].…”

Kinetic study of catalytic CO 2 hydration by metal-substituted biomimetic carbonic anhydrase model complexes

“…Since more than one million tons per year of CO 2 has to be sequestered, the importance of the development of CO 2 capture methods has been increasing. Recently, methods using CA have been of considerable interest because the enzyme hydrates and rapidly converts CO 2 to carbonic acid at a rate of at least 10 6 M −1 s −1 [7,11,12]. However, because of the significant effects of temperature and operating pH on the catalytic activity as well as drawbacks of enzyme stability and cost, utilization of CA in an actual process is difficult [13,14].…”

A State‐of‐the‐Art Update on Integrated CO2 Capture and Electrochemical Conversion Systems

“…This structure can easily bind water molecules and decrease to a great extent its pK a (from 14 to 6.9), promoting its deprotonation and the formation of a fixed activated OH − structure which then binds CO 2 to form bicarbonate (Figure 1) . [48] The rate constant of the CO 2 hydration in CA is at least 10 6 M −1 s −1 , thus there is interest in integrating these systems in current CO 2 capture technologies as this could significantly enhance the capture rate [49,50] . One of the strategies is to integrate the biomimetic system in components such as membranes or porous materials.…”

“…[48] The rate constant of the CO 2 hydration in CA is at least 10 6 M À 1 s À 1 , thus there is interest in integrating these systems in current CO 2 capture technologies as this could significantly enhance the capture rate. [49,50] One of the strategies is to integrate the biomimetic system in components such as membranes or porous materials. This increases the reusability of the enzyme as well as the mechanical resistance of the capturing material.…”