High-level production of Serratia proteamaculans metalloprotease using a recombinant ABC protein exporter-mediated secretion system in Pseudomonas fluorescens

• The Serratia proteamaculans metalloprotease was secreted by the heterologous ABC protein exporter in E. coli and P. fluorescens.
• The recombinant P. fluorescens produced about 34.8-fold higher amount of SPP than E. coli.
• ABC exporter-mediated secretion of SPP was improved by changing growth medium and aeration condition.

Serratia proteamaculans metalloprotease (SPP) was successfully secreted by a heterologous ABC protein exporter, the Pseudomonas fluorescens TliDEF, in recombinant host strains. Escherichia coli and P. fluorescens cells containing the SPP-encoding gene showed the extracellular protease activity only when the TliDEF-encoding gene cluster was coexpressed. Recombinant P. fluorescens produced an approximately 34.8-fold higher amount of extracellular SPP than did E. coli. The use of a more nutrient-rich medium and controlled dissolved oxygen conditions was effective in increasing SPP secretion in P. fluorescens batch fermentation (an 8.7-fold increase from 41.8 U/mL to 365.2 U/mL). Therefore, SPP, which could not be secreted without an ABC protein exporter, was produced in large quantities by applying the heterologous TliDEF exporter in P. fluorescens. The results also suggest that the use of the ABC protein exporter in P. fluorescens could be an efficient production platform for an industrially promising type I secretion pathway-dependent enzyme.