According to instructions of ActiCHO Feed-B Powder Base CD, it is dissolved by adding NaOH and has an alkaline pH about 11. According to our detections, feed B contains a concentrated solution of Tyr, Cys and Trp. As we know, besause of low solubility in neutral solution,Tyr, Cys and Trp can be dissolved in alkaline (NaOH) solution, but they can be dissolved in acidic (HCl) solution too, could we use HCl instead of NaOH to dissolve feed B or the three amino acids? I confused that,why in all literatures (patents and papers) they use NaOH only to dissolve high concentrations of Tyr and Cys? Does feed B has some other components such as Vitamin B2? During long term CHO cell culture, if we add too much NaOH into bioreactors, in late phase the capacity of NaHCO3/Na2CO3 buffer system is too strong to control pH within the desired range, and pCO2 is very high.
Glucose metabolism will produce lactic acid, so adding a feed powder that is basic helps to counter that problem. If you use HCl/NaOH as your pH control strategy, try changing it to CO2/NaCO3. Sparge CO2 into the bioreactor using a bubble sparger to lower pH (Link it to pH control through controller) and us NaCO3 as base (J. Piret, 2007 paper I believe) as it is much more efficient. This keeps the buffer system with its linked components. Finally, through the headspace, use 10% vessel volume/minute air to strip CO2 that accumulates from metabolism...this flow rate should keep pCO2 below 70 mm Hg. If PCO2 is higher, increase the airflow rate accordingly. Hope that helps. David Petch....regarding the other questions, I suspect it has to do more with greater stability of compounds at a higher pH.
Hello Jing Liu, I'm curious to know if you had any success regarding making ActiCHO Feed B with HCl. I recently tried a shake flask study with an acidic Feed B. However, the growth and productivity were much lower compared to control. I have been thinking of modifying feeding strategy to suit the acidic feed B better.
Hi Yogender Gowtham, I suggest you that, during the early phase of your culture, using alkaline feed B, and during the middle to late phase,using acidic feed B. In shake flask pH can not be controlled well, I think you should run the experiments in stirred tank reactor and monitor pCO2. Concentration of HCl and NaOH is 1.2 M in feed B respectively, if you have higher amino acids concentrations, they should higher too.
Thank you Jing. Yes, I was thinking on similar terms too. Looking back on the data, pH was not controlled well and had an impact on the lactate production/consumption.
I had an additional question, at what acidic pH does the feed B dissolve for you? Last time I tried, it was less than 1.0. I think I was using 1N HCl.
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