Accelerated Uptake of CO2 Catalyzed by Immobilized Thermophilic Carbonic Anhydrase on Dispersed Aminated Mesoporous Silica

TL;DR

This study shows that attaching carbonic anhydrase enzymes to a special type of silica improves their stability and activity for capturing CO2, even at high temperatures.

Contribution

The study demonstrates that immobilizing thermophilic carbonic anhydrase on aminated mesoporous silica enhances its thermal stability and CO2 capture efficiency.

Findings

Adsorbed pmCA and bCA retained high activity for 14 days at 40–65 °C and 4 days at 90 °C, unlike free enzymes.

The maximum adsorption capacities were 1.4 g pmCA and 2.1 g bCA per gram of aminated SBA-15.

IR spectroscopy confirmed increased bicarbonate formation with immobilized CA in CO2-loaded dispersions.

Abstract

Efficient and durable biocatalysts are important for
sustainable
CO2 capture technologies, but enzyme stability often limits
their use under harsh process conditions. Here, we evaluate carbonic
anhydrases (CAs) adsorbed onto aminated mesoporous SBA-15 as biocatalysts
for CO2 capture under the hypothesis of adsorption-induced
thermal stabilization. Carbonic anhydrase from the thermophilic bacterium Persephonella marina (pmCA) and commercial bovine
erythrocyte carbonic anhydrase (bCA) were used. Enzyme adsorption
isotherms for pmCA and bCA onto the aminated SBA-15 were established,
along with desorption tests. Adsorbed and free pmCA and bCA were incubated
at 40–90 °C for 14 d. The structural integrity and possibility
of amine leaching of the incubated (90°, 14 d) aminated SBA-15
were analyzed by X-ray diffraction (XRD) and NMR spectroscopy. The
reaction product speciation in CO2-loaded catalyzed and
uncatalyzed dispersions was monitored using infrared (IR) spectroscopy.
The maximum enzyme adsorption capacities were established to be 1.4
± 0.2 g pmCA·g-aminated SBA-15–1 and 2.1
± 0.5 g bCA·g-aminated SBA-15–1, with
no detectable desorption. Adsorbed pmCA and bCA maintained high activity
for 14 d at 40–65 °C and for 4 d at 90 °C, whereas
free enzymes lost activity within 4 d at all temperatures. The XRD
patterns of the heat-treated (90 °C, 14 d) aminated SBA-15 indicated
a full collapse of the mesostructure. IR spectroscopy confirmed enhanced
HCO3
– formation in the presence of immobilized
CA. Overall, enzyme adsorption onto the aminated SBA-15 significantly
improved the thermal stability and activity of pmCA and bCA compared
to the free enzymes, demonstrating the potential of adsorbed CAs for
biocatalysis.

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