Effect of Carbonic Anhydrase on CaCO₃ Crystallization in Alkaline Solution

Abstract

The effect of bovine carbonic anhydrase (CA) on calcium carbonate (CaCO 3 ) crystallization was investigated. A new method was developed to estimate the biocatalytic activity of CA in alkaline solution. The CA was immobilized within polyurethane (PU) foam, and compared its biocatalytic activity with the free-CA and bare-PU foam. A minireactor was created in a calcium hydroxide (Ca(OH) 2 ) solution in order to control the CO 2 transfer rate, and reproducible results were obtained. It was found that the free-CA lost its activity in less than 6 min at pH 12.5 in alkaline Ca(OH) 2 solution. The CaCO 3 crystallization rates for the immobilized-CA were found to be a U-shape, relatively lower at lower immobilized-CA amounts compared to those for the free-CA and bare-PU foam and higher when the amount of immobilized-CA increased. It was concluded that a higher immobilized-CA amount is required to accelerate the CaCO 3 crystallization rates in Ca(OH) 2 solution.

The Carbonation of Wollastonite: A Model Reaction to Test Natural and Biomimetic Catalysts for Enhanced CO2 Sequestration

“…In the case of Ca, its decrease in concentration occurred earlier and faster in the presence of the enzyme. This is in agreement with previous studies reporting that CA catalyzes calcite precipitation [31,39]. Figure 2c shows the pH evolution during the carbonation test.…”

“…CA is one of the fastest enzymes known, with a turnover of up to 10 6 s −1 [34]. Such a biocatalyst has been found to be effective for enzymatic pre-and post-combustion (flue gas) CO 2 capture [6,38], and for accelerated ex situ CO 2 capture and storage via carbonation of industrial alkaline brines [32], Ca(OH) 2 solutions [39] and pastes [31], and Mg(OH) 2 slurries [34], as well as solutions produced during the pH-swing process [40,41]. In addition to its "hydrase" catalytic activity, CA also acts as an "esterase" enzyme, being able to hydrolyze a range of ester bonds [38].…”

Acceleration of dolomitization by zinc in saline waters

“…Moreover, zinc drives mineralization leading to the formation of kidney stones 26 or bladder stones, documented to contain dolomite in some cases 27 . Furthermore, carbonic anhydrase (CA), a Zn-containing metalloenzyme, accelerates the formation of calcium carbonate, for example in sponge spicules 28 , and in alkaline solutions 29 . The role of zinc in each of these earth science, chemistry, and biology contexts is striking; yet, no previous research has investigated the impact of dissolved zinc on the reaction pathways and kinetics of dolomitization.…”

The multiple roles of carbonic anhydrase in calcium carbonate mineralization

“…2,28 Each droplet provides a constrained environment and enables the in situ analysis of the evolution of the chemistry of the system (pH, [Ca 2+ ] and [CO 3 2− ]) as well as the kinetics and mechanisms of the different precipitation events and mineral phase transformations without interference from background electrolytes. 28 Carbonation in the CaIJOH) 2 -H 2 O system has been shown to be relevant for several technological processes including CO 2 mineral sequestration 29 or the biomimetic synthesis of functional CaCO 3 structures such as microlens arrays. 30 However, as in the case of other in vitro systems thoroughly used for biomimetic calcium carbonate precipitation, such as the gas diffusion method based on (NH 4 ) 2 CO 3 decomposition, 5 its chemistry, specially pH values, might not be representative of in vivo biomineralization.…”