Glucose-based feeding strategy development in recombinant human growth hormone production by ichia pastoris for semi-batch bioreactor operation

Keskin, Abdullah
The aim of this study was to develop an effective feeding strategy to enhance recombinant human growth hormone (rhGH) production by Pichia pastoris Mut+ strain harboring pGAPZαA::hGH which is integrated to glyceraldehyde-3-phosphate dehydrogenase gene (GAP) locus of P. pastoris. In this context, eight semi-batch bioreactor experiments were conducted at pilot-scale; their batch phase was same in which glycerol was used as the sole carbon source. For semi-batch operation phase, eight feeding strategies were designed using exponential substrate feeding, constant substrate feeding, specific substrate consumption rate based substrate feeding, and combination of these feeding modes. The feeding strategies were designed by using three different pre-determined specific growth rates, μ0=0.10, 0.15, and 0.175 h-1, two constant volumetric flow rates of glucose, Q(t≥15 h) =12 ml h-1 or Q(t≥11 h) =24 ml h-1, and one constant specific glucose consumption rate, qS=0.05 g g-1 h-1. Further, to investigate the effects of carbon sources, glucose and pre-treated molasses were used. The best feeding strategy was the one conducted based on exponential glucose feeding with the pre-determined specific growth rate of μ0= 0.15 h-1 wherein the highest rhGH was attained as CrhGH = 508 mg L-1 at t=19 h and the cell concentration was CX =65.4 g L-1. The overall product and cell yield on total substrate were obtained as Y’P/S = 1.9 mg g-1 and Y’X/S=0.22 g g-1, respectively.