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Buttery Popcorn Odor in Contaminated Expression Prep


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#1 ChrisR

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Posted 12 February 2010 - 08:57 PM

Hello,

I am trying to overexpress my protein of interest using standard recombinant bacterial expression techniques of batch fermentation in shaker flasks. I have had this problem twice in the past 3 years, where a prep will appear to grow very slowly, then will suddenly flourish 24-48 hours after it is started. The media will turn a yellowish color and smell very strongly of buttered popcorn, and the resulting cell pellet will be much darker in color than the usual E. coli pellet. Oh yeah, and I'll get no protein out of my prep. I'm curious whether anyone knows what common bacteria/fungus/yeast/whatever could possibly get into a culture containing antibiotics and take it over. Has anyone else experienced this phenomenon? Is this something I can prevent in the future in some way?

Thank you in advance,
Chris

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University of Arizona

#2 Vini

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Posted 13 February 2010 - 06:24 AM

Hello,

I am trying to overexpress my protein of interest using standard recombinant bacterial expression techniques of batch fermentation in shaker flasks. I have had this problem twice in the past 3 years, where a prep will appear to grow very slowly, then will suddenly flourish 24-48 hours after it is started. The media will turn a yellowish color and smell very strongly of buttered popcorn, and the resulting cell pellet will be much darker in color than the usual E. coli pellet. Oh yeah, and I'll get no protein out of my prep. I'm curious whether anyone knows what common bacteria/fungus/yeast/whatever could possibly get into a culture containing antibiotics and take it over. Has anyone else experienced this phenomenon? Is this something I can prevent in the future in some way?

Thank you in advance,
Chris

Graduate Student
University of Arizona


hi , i hv never faced such a problem with E.coli culture but i guess it would be a nice idea to have your hood and shaker fumigated (i guess you would have already tried out that, though). Are your other labmates facing the same problem? Also, i hope your antibiotics are working fine!

#3 HomeBrew

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Posted 13 February 2010 - 12:51 PM

That's probably diacetyl being produced -- at least when diacetyl gets produced when beer is fermenting, it will put off a buttery aroma... Any reason to suspect you picked up a yeast contaminant?

#4 ChrisR

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Posted 16 March 2010 - 09:37 AM

That's probably diacetyl being produced -- at least when diacetyl gets produced when beer is fermenting, it will put off a buttery aroma... Any reason to suspect you picked up a yeast contaminant?



I'm sure it's not out of the question that yeast found it's way in there and survived the antibiotics to grow and take over the flask. Thank you for identifying the compound that is likely responsible for the smell.




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