3.4.1 Reducing the adaptation time to methanol induction environments
When the second methanol induction phase was initiated by feeding methanol, MutS P. pastoris cells has to take a long-term time to adapt the environment of methanol induction by synthesizing alcohol oxidase (AOX) to drive methanol metabolism. In general, the stoppage of this adaptation phase could be easily and indirectly reflected by the drop of DO and the increased OUR (online data). As shown in Fig.4, when using the periodic DO control strategy (strategy C), the drop of DO and the increased OUR occurred at about 3 h during the methanol induction phase, which was only one half of that obtained with the “high DO-low glycerol concentration” control strategy (strategy A) when using same methanol induction strategy. As the batch using “low DO-high glycerol concentration” control strategy (strategy B), the drop of DO and the increased OUR were not observed throughout the entire methanol induction phase (data not shown), leading to the failure of hLYZ production.