In this study, the antihypertensive peptide WQVLPNAVPAK was selected for the synthesis of the gene encoding the hexameric peptide angiotensin I-converting enzyme inhibitory peptide (ACEIP) based on the codon preference of Escherichia coli. The synthetic gene was cloned into the expression vector pET30a to construct recombinant plasmid pET30a-ACEIP. The recombinant plasmid was identified by double digestion with restriction endonucleases NdeI and HindIII and polymerase chain reaction (PCR), and transformed into competent E. coli BL21 (DE3) cells to construct the expression system E. coli BL21(DE3)/pET30a-ACEIP, which was induced with isopropyl-β-D-thiogalactopyranoside (IPTG) at a final concentration of 0.8 mmol/L. A clear band of 8.7 kDa was seen on Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The hexameric peptide ACEIP was purified by Ni²⁺ affinity chromatography and the expression of the fusion protein was 61.30 mg/L. The expression of ACEIP was 57.84 mg/L. The half-maximal inhibitory concentration (IC₅₀) of the hexameric peptide was 6.39 mg/mL after trypsin digestion, whose ACE inhibitory activity was higher than that of the monomeric peptide WQVLPNAVPAK (IC₅₀ of 12.34 mg/mL).

Coexpression of formate dehydrogenase (FDH) and ribitol dehydrogenase (RDH) in Escherichia coli was used for the synthesis of Allitol from D-psicose. FDH was coexpressed with RDH for continuous NADH regeneration. The results revealed that the optimum conditions for allitol production occurred at pH 7.0 and 30 ℃. Allitol reached the maximum yield of 19.2 mg at 2.0% substrate concentration after 48 hours. Using D-psicose as a substrate,allitol was successfully produced using an engineered E. coli coexpressed with RDH and FDH.