Process parameters optimization to produce the recombinant protein CFP10 for the diagnosis of tuberculosis

The aim of this study was to evaluate the parameters that affect the production of the recombinant 10 kDa culture filtrate protein (CFP10), a promising reagent of high specificity for intradermoreaction and other antigen-based methods used in the diagnosis of tuberculosis. Conditions of Escherichia coli growth temperature, induction temperature and IPTG-inducer concentration were evaluated in shake flasks and dissolved O₂ concentrations of 15 and 30% were evaluated in a bioreactor. The process parameters defined on small scale were: growth temperature between 30 and 37 °C, induction temperature of 26 °C and IPTG concentration of 0.12 mM. The process conducted with 15% dissolved O₂ presented a recombinant protein yield of 78.6 mg g^-1 biomass and a proportion of recombinant protein (insoluble fraction) in relation to total insoluble protein of 72%, at the time of maximum productivity. The operation with 30% dissolved O₂ resulted in lower recombinant protein yields of 62.9 mg g^-1 biomass and 20% in relation to total insoluble protein, but in higher overall concentration in the culture broth (69.2 mg L^-1versus 48.3 mg L^-1). The protein identity was confirmed by mass spectrometry, showing high similarity to CFP10, 10 kDa of Mycobacterium tuberculosis H37Rv (score 95), and the purified antigen presented reactivity by the Western blotting assay.