Highly Efficient Extracellular Production of Recombinant Streptomyces PMF Phospholipase D in Escherichia coli

Abstract

To achieve efficient bio-production of phospholipase D (PLD), PLDs from different organisms were expressed in E.coli. An efficient secretory expression system was thereby developed for PLD. First, PLDs from Streptomyces PMF and Streptomyces racemochromogenes were separately over-expressed in E.coli to compare their transphosphatidylation activity based on the synthesis of phosphatidylserine (PS), and PLDPMF was determined to have higher activity. To further improve PLDPMF synthesis, a secretory expression system suitable for PLDPMF was constructed and optimized with different signal peptides. The highest secretory efficiency was observed when the PLD * (PLDPMF with the native signal peptide Nat removed) was expressed fused with the fusion signal peptide PelB-Nat in E. coli. The fermentation conditions were also investigated to increase the production of recombinant PLD and 10.5 U/mL PLD was ultimately obtained under the optimized conditions. For the application of recombinant PLD to PS synthesis, the PLD properties were characterized and 30.2 g/L of PS was produced after 24 h of bioconversion when 50 g/L phosphatidylcholine (PC) was added.