thank you Luiza,

but i'm not understand this very well,  ( E.coli cells produce large quantities of acetic acid if the growth medium contains little or no oxygen causing the growth medium to reach pH 4 or lower. Acetic acid is the major metabolic inhibitor under anaerobic growth condition. However, with proper aeration, E.coli cells will be able to use many organic acids as carbon sources and the pH of the growth medium will be maintained at near neutral or basic ranges.)

how acetic acid produce in anaerobic growth condition?? how use organic acids as carbon sources??

I don't understand you guys. Acetic acid production requires oxygen, so acetic acid production clearly won't happen during anaerobic culture.

True, I should probably have read the initial discussion more carefully. It doesn't necessarily have to be acetic acid produced though.

dear Luiza

its now clear

thank you a lot