Effect of co‐substrate sorbitol different feeding strategies on human growth hormone production by recombinant Pichia pastoris

BACKGROUND Effects of co‐substrate sorbitol different feeding strategies on recombinant human growth hormone ( rhGH ) production by Pichia pastoris hGH ‐Mut + were investigated by eight designed experiments grouped as: (i) fed‐batch methanol feeding without the co‐substrate; (ii) fed‐batch methanol feeding with pulse sorbitol feeding; (iii) fed‐batch methanol feeding together with fed‐batch sorbitol feeding at t  = 0–15 h, followed by fed‐batch methanol feeding; and (iv) fed‐batch methanol and sorbitol feeding at t  = 0–30 h, followed with fed‐batch methanol feeding . RESULTS The highest rhGH and cell concentrations were achieved, respectively, as 0.64 g L −1 and 105 g L −1 at t  = 42 h of induction phase, with the strategy where methanol was fed to the system at a pre‐determined feeding rate of μ M0 =0.03 h −1 , and sorbitol concentration was kept at 50 g L −1 at t  = 0–15 h of the rhGH production phase where the specific growth rate on sorbitol was μ S0 =0.025 h −1 . The overall cell and product yield on total substrate were found as 0.26 g g −1 and 2.26 mg g −1 , respectively . CONCLUSION This work demonstrates that co‐carbon source, sorbitol, feeding strategy is as important as methanol feeding strategy in recombinant protein production by Mut + strains of P. pastoris . © 2012 Society of Chemical Industry