Hi fellows and researchers, I am doing Pichia pastoris fermentation, GS115 strain containing pPIC5a, 50-L scale. I follow the Invitrogen protocol and try hard to get the recommended biomass before induction phase. However, my strain did not reach that level in time, I try to extend the growth phase and then get a lower protein level. I assume that the protocol did not work with my strain or the bioreactor operation.

Other problems I have faced is that the bioreactor can not adjust the methanol feeding rate automatically. I have to adjust that manually. Do you have any idea to solve that, or detect the methanol accumulation to adjust properly. According to this paper, authors recommended NH4OH assumption indicating methanol accumulation without instruction. How can I do that?

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