Enhancing extracellular production of lipoxygenase in Escherichia coli by signal peptides and autolysis system

Background Lipoxygenase (LOX) is a non-heme iron containing dioxygenase that is widely used to improve food quality and produce active drug intermediates and biodiesel. Escherichia coli is one of the most widely used host microorganisms for recombinant protein expression; however, its weak extracellular secretion ability precludes its effective production of recombinant proteins into the extracellular environment. To facilitate subsequent characterization and application of LOX, improving its secretion efficiency from E. coli is a major challenge that needs to be solved. Results Several strategies were adopted to improve the extracellular secretion of LOX based on the signal peptides and cell wall permeability of E. coli. Here, we studied the effect of signal peptides on LOX secretion, which increased the secretory capacity for LOX marginally. Although surfactants could increase the permeability of the cell membrane to promote LOX secretion, the extracellular LOX yield could not meet the requirements of industrialization production. Subsequently, an autolysis system was constructed in E. coli based on the bacteriophage lysis gene phi X174-E to enhance the production of extracellular proteins. Thus, the extracellular production of LOX was achieved and the content of inclusion bodies in the cell was reduced by optimizing cell lysis conditions. The extracellular LOX yield reached 368 +/- 1.4 U mL(-1) in a 5-L bioreactor under optimized lysis conditions that is, an induction time and temperature, and arabinose concentration of 5 h, 25 degrees C, and 0.6 mM, respectively. Conclusions In this study, the different signal peptides and cell autolysis system were developed and characterized for extracellular LOX production in E. coli. Finally, the cell autolysis system presented a slight advantage on extracellular LOX yield, which also provides reference for other protein extracellular production.

Automated summary

Several strategies were adopted to improve the extracellular secretion of LOX from Escherichia coli, including signal peptides and cell wall permeability. Despite marginal improvements in LOX secretion capacity with signal peptides, the extracellular LOX yield was not sufficient for industrial production. An autolysis system based on the bacteriophage lysis gene phi X174-E was constructed to enhance extracellular protein production, leading to an optimized extracellular LOX yield of 368 +/- 1.4 U mL(-1) in a 5-L bioreactor.