Tumor necrosis factor-alpha (TNF-α) is an inflammatory cytokine that plays a major role in immune regulation, homeostatic function, and cellular organization. The present study was undertaken to overproduce recombinant human TNF-α (rhTNF-α) in Escherichia coli (E.coli) in high cell density culture. The use of a codon-optimized gene and strong promoter-based (T7) expression system, choice of Terrific Broth (TB) as medium, and subsequent optimization of culture conditions in shake flasks resulted in production of 0.95 g/L insoluble rhTNF-α comprising upto 50% of total cellular protein (TCP) The protein yield further increased upto 1.26 g/L in 1 L TB medium batch culture in bioreactor with the controlled temperature, pH, and dissolved oxygen. In a series of chemostats operated at dilution rates of 0.2 h-1, 0.3 h-1, 0.4 h-1 and 0.5 h-1 the specific growth rate (μ) positively correlated with specific yield (Yp/x) and a maximum yield of 164 mg/g DCW was obtained at μ = 0.4 h-1 within 4 h post-induction. A fed-batch cultivation in TB with an exponential feeding profile (μ = ∼0.4 h-1) of concentrated feed resulted in an accumulation of 5.5 g/L of rhTNF-α within 14 h of cultivation which accounted for ∼29% of TCP.
Keywords: Escherichia coli; TNF-α; chemostat culture; expression kinetics; fed-batch culture; optimization; overproduction.