Heterologous expression, purification and functional characterization of recombinant serratiopeptidase from Serratia...

Serratiopeptidase, a proteolytic enzyme with therapeutic applications, is traditionally produced from the bacterium Serratia marcescens. Recombinant production of serratiopeptidase in Escherichia coli offers a safer alternative to the biosafety concerns of the producer. Present study involves cloning and heterologous expression of thermoactive serratiopeptidase gene from S. marcescens AD-W2 in E. coli K12 in pET28a plasmid. Optimized expression conditions i.e. 37 °C, OD₆₀₀ 5, 5% L-rhamnose, 5mM IPTG, and 50% dissolved oxygen led to the final yield of 190 mg/g serratiopeptidase (4747 mg protein/L within 9 h in a bioreactor. Purification and refolding of recombinant serratiopeptidase was performed in a single step using Tangential Flow Filtration (TFF) and diafiltration process. The purified recombinant serratiopeptidase exhibited specific activity of 1800 Units/mg protein, with an optimal activity at pH 9.0 and temperature 50 °C. The value of kinetic constant K_m was calculated as 1.38 mg/mL for casein. The recombinant serratiopeptidase demonstrated comparable anti-inflammatory activity to the commercially available serratiopeptidase, inhibiting nitric oxide release and pro-inflammatory cytokine production in LPS-stimulated murine macrophage cell line RAW 264.7. The study reveals that the recombinant serratiopeptidase produced in E. coli K12 holds promising source of safe and effective anti-inflammatory agent.