Response surface optimization for lactose inducible expression of recombinant fructosyl peptide oxidase enzyme in Escherichia coli

Background: Fructosyl peptide oxidase (FPOX), a flavoenzyme classified as an oxidoreductase, serves as a diagnostic enzyme in HbA1c measurement tests. This research focuses on statistically optimizing lactose-induced expression to produce soluble recombinant FPOX. Methods: A Plackett–Burman design was used to identify key factors influencing enzyme expression, which were further optimized using a central composite design. Results: The results indicated that glycerol, yeast extract, tryptone, and lactose significantly affected FPOX activity. The maximum enzyme activity and biomass concentration were achieved under the optimum conditions of yeast extract (10.12 g/L), tryptone (13.44 g/L), K₂HPO₄ (2.62 g/L), and lactose (12.79 g/L). When the lactose-inducible induction strategy was examined at the shake flask scale, FPOX activity (28.77 U/mL) was 18.5-fold higher than with the IPTG induction protocol. Additionally, the increased biomass yield (49.0 g/L compared to 22.0 g/L) further supported the appropriateness of utilizing lactose-inducible expression. Conclusion: Together, our findings indicated that the design of experiment methodology can be utilized effectively to enhance the production of the FPOX enzyme with lactose as the inducer.