Feeding strategy design for recombinant human growth hormone production by Bacillus subtilis

Defined and semi-defined medium-based feeding strategies were developed to enhance recombinant human growth hormone (rhGH) production by Bacillus subtilis BGSC-1A178 (scoC (-)) strain carrying pMK4::pre(subC)::hGH. Defined medium-based feeding strategies were designed by exponential feeding of glucose and (NH4)(2)HPO4 at two pre-determined specific growth rates, A mu (0) = 0.10 and 0.17 h(-1). Semi-defined medium-based feeding strategies were designed by exponential feeding of substrate solution consisting of glucose, (NH4)(2)HPO4, peptone, and trace salt solution (PTM1) at three pre-determined specific growth rates, A mu (0) = 0.10, 0.17, and 0.25 h(-1). At all the strategies applied, transition cultivation time from batch to fed-batch operation was t (T) = 4 h. The highest rhGH concentration was obtained as C (rhGH) = 0.5 g L-1 with semi-defined medium-based feeding strategy designed with A mu (0) = 0.25 h(-1) using feed substrate stock solution containing 200 g L-1 glucose, 117 g L-1 (NH4)(2)HPO4, 100 g L-1 peptone, and 5 mL L-1 PTM1 at t = 22 h when the cell concentration reached to C (X) = 8.29 g L-1. The overall product and cell yields on glucose were obtained as = 7.21 mg g(-1) and = 0.12 g g(-1), respectively. The results indicate the requirement of designing continuous feed stream in fed-batch production to enhance rhGH production by r-B. subtilis.