Comparison between constant methanol feed and on-line monitoring feed control for recombinant human growth hormone production by Pichia pastoris KM71

Two methanol feeding methods, namely constant methanol feed and on-line monitoring feed control by methanol sensor were investigated to improve the production of recombinant human growth hormone (rhGH) in high cell density cultivation of Pichia pastoris KM71 in 2 L bioreactor. The yeast utilized glycerol as a carbon source for cell growth and yeast cells were accumulated to high cell density. Cell dry weight concentration around 140 to 150 g/l was obtained before entering the methanol induction period. Methanol was applied to express rhGH after high cell accumulation. The constant methanol feed rate at 0.009 l/h was applied to the cultivation to compare with the on-line monitoring feed control of methanol concentration. The highest amount of rhGH around 501 mg/l was obtained by using on-line monitoring feed control of methanol at the set point of methanol concentration at 4.0 g/l. After achieving the best result from the on-line monitoring feed control method, the experiment was further carried out to investigate the optimal methanol concentration. On-line controlling of methanol concentrations at 2.0, 4.0 and 8.0 g/l were investigated. The result shows that high amount of rhGH was achieved by controlling the methanol level at the set point of 4.0 g/l.Key words: Recombinant human growth hormone, Pichia pastoris, fed-batch cultivation, methanol feeding control