New and efficient purification process for recombinant human insulin produced in Escherichia coli

A new and efficient purification process for recombinant human insulin production was developed by exploring new resins and optimizing purification steps from E. coli inclusion body washing to insulin polishing. A combined additives inclusion body wash protocol drastically improved efficiency in clarifying ZZ-proinsulin samples. ZZ-proinsulin recovery increased three-fold under optimized solubilization and sulfitolysis incubation temperature and duration. Desalting with Bio-Gel P4 and P6 resulted in higher sample loading and product recovery compared to conventional resins. A higher recovery (96%) and purity (81%) of ZZ-proinsulin were achievable with the Nuvia S cation exchanger for proinsulin purification compared to a reported process using expensive affinity chromatography resin. As the first step for insulin purification, process scale-up is more economical and practical when Nuvia HR-S cation exchanger was used instead of commonly used reversed-phase chromatography. Nuvia HR-S was highly effective in removing ZZ fusion protein (90% removal) after enzymatic cleavage, although ZZ fusion protein has a very close theoretical pI to human insulin, which was supposedly challenging to be removed by cation exchange chromatography. Also, insulin can be eluted at a lower ethanol % using Nuvia HR-S compared to other reported processes and is thus more environmentally sustainable. Recombinant human insulin was obtained with over 98% purity in just a single reversed-phase polishing step, which is comparable to the reference standard. The process workflow presented here can be potentially applied for the development of purification workflow for insulin analogs or other peptide products derived from E. coli inclusion body. Key points • Drastic efficiency improvement for inclusion body wash with combined additives. • High recovery of proinsulin purification with high capacity cation exchange resin. • Effective removal of fusion tag at lower ethanol % with high-resolution resin.