Improvement of Soluble Expression, Stability, and Activity of Acetaldehyde Lyase by Elastin-like Polypeptides Fusion for Acetoin Production from Acetaldehyde

To achieve the large-scale, low-cost preparation of acetaldehyde lyase (ALS), elastin-like polypeptides (ELPs) as non-chromatographic purification tags were employed to develop an ELP-ALS fusion protein in <i>Escherichia coli</i>. Induction expression results demonstrated that the ELPs tag efficiently improved the soluble expression of the ALS enzyme. Through two rounds of inverse transition cycling (ITC), highly pure ELP-ALS was obtained with an enzyme recovery rate of 85.77%, outperforming Ni²⁺-affinity chromatography (66.80%). The comparative analysis of enzymatic properties revealed that ELP fusion markedly improved the stability and substrate tolerance of the ALS enzyme. Kinetic parameter analysis under identical conditions showed that ELP-ALS possessed a <i>V</i>_max of 15.25 U/mg and a <i>k</i>_cat/<i>K</i>_m of 73.05 s^-1·M^-1, representing 1.86-fold and 2.97-fold improvements over His-ALS, respectively. Fed-batch reaction using ELP-ALS and acetaldehyde as biocatalyst and substrate, respectively, yielded 95.92 g/L acetoin with 49.32% increase compared to His-ALS (64.24 g/L). These results demonstrated the application potential of ELP-ALS as a promising biocatalyst for acetoin production from acetaldehyde due to its lower preparation cost, higher biocatalytic efficiency, better stability, and substrate tolerance.