Escherichia coli (E. coli) is a popular system for recombinant protein production, owing to its low cost and availability of genetic tools. However, the expression of soluble recombinant proteins remains an issue. As such, various solubility-enhancing and yield-improving methods such as the addition of fusion tags have been developed. This study focuses on a small solubility tag (NT11), derived from the N-terminal domain of a duplicated carbonic anhydrase from Dunaliella species. The small size of NT11 (