A Streptomyces lividans SipY deficient strain as a host for protein production: standardization of operational alternatives for model proteins

Abstract

BACKGROUND: Extracellular protein production by Gram-positive bacteria, such as Streptomyces, may be complementary to current established protein production processes. The performance of a Streptomyces lividans mutant strain, deficient in the major signal peptidase (SipY) is investigated for the production of proteins secreted via the secondary Tat pathway. RESULTS: The SipY deficient strain has shown advantages over the wild type strain, in terms of extracellular productivity, specific activity and rheological behaviour. Two operational modes, batch and fed-batch, have been studied using mannitol as carbon source. The results showed that two successive mannitol additions in fed-batch mode led to improved secretory protein production using Streptomyces agarase as a model protein. This production process was also explored for the Tat secretory protein S. lividans laccase. The predicted sequence for the pre-laccase coding sequence has been cloned into the mutant strain under the control of the agarase promoter. Batch and fed-batch laccase production, using either mannitol or glucose as carbon source, have been developed and quantified. CONCLUSIONS: The usefulness of a Streptomyces lividans SipY deficient strain as protein producer has been demonstrated. A proposed operating mode with substrate additions has been employed for the optimisation of Tat proteins production, although some adjustments might be necessary depending on the secretory protein. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry