Dear all,
I have a similar problem in my anaerobic fermentations (glucose fermentation by C.beijerinckii). I flush the fermenter with N2 (0.5 l/min) entire time and stir.
I prepare my anaerobic media accordingly so that there is no dissolved oxygen in the begining of the fermentation. However, during exponential growth phase, dissolved oxygen level increases drastically, up to 60%. The problem is not the probe nor the equipment. I observed the same pattern in different setups (Aplikon fermenters and microreactor fermentations).
Does anyone experience a similar thing? If yes, how did you overcome the problem?
P.S.I am suspecting oxygen production by the bacteria triggered by a metabolic change, but I haven't found anything about the in the literature.
Dear Harifara,
Thank you for your answer. I used lab purity glucose and xylose, so there aren't any impurities in the substrate such as furfural. However, the logic behind it is interesting and it is worth to have a closer look at the medium components.
Dear Hendrik,
I used high purity nitrogen (grade 6.0) but without an oxygen filter. It is good to know.
Dear Birgen
Have you checked your system to monitor oxygen generation without flushing N2?
Please make sure algae is not present in your system. If you get any photosynthetic organism to be active then you get oxygenation path, that may cause DO generation.
hi,
filter see for example:
http://www.agilent.com/en-us/products/lab-supplies/chromatography-spectroscopy/gas-management/gas-clean-purification-system
and
excellent way to meassure oxygen:
https://www.presens.de/products/detail/microx-4-trace.html
Dear Ghasem,
I haven't checked it without flushing. I should do it next time. For the case of contamination or algae, I should do further investigation.
Thank you
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