Heterologous expression of carbonic anhydrase in Acinetobacter sp. Tol 5 for whole-cell biocatalysis

Abstract

Carbonic anhydrase accelerates the hydration of carbon dioxide (CO2) and is an attractive biocatalyst for carbon capture and utilization. Acinetobacter sp. Tol 5 shows high adhesiveness via its cell-surface protein AtaA. We previously demonstrated its application to bacterial immobilization and gas-phase bioproduction. Here, we developed Tol 5 cells expressing carbonic anhydrase and evaluated CO2 conversion ability as whole-cell biocatalysts. A codon-optimized carbonic anhydrase from Sulfurihydrogenibium yellowstonense (SyCA) was produced in the cytoplasm, but the cells showed little activity as a whole-cell biocatalyst. To enhance activity, we fused six signal peptides (SPs) to SyCA for periplasmic expression. The Omp38-SP fusion of SyCA was properly processed to the mature size, yielding higher whole-cell activity. By contrast, the other constructs were either undetectable or remained unprocessed, resulting in lower activities. These results show that periplasmic expression of SyCA is important for efficient CO2 hydration in Tol 5 cells as whole-cell biocatalysts.