Levo-2,3-butanediol (2,3-BD)-mediated feed-back inhibition is a major physiological impediment to 2,3-BD yield.

Increased levo-2,3-BD concentration in the fermentation medium triggers backward conversion of 2,3-BD to acetoin.

Levo-2,3-BD mediated toxicity engenders increase in meso-2,3-BD accumulation during fermentation by P. polymyxa.

Meso-2,3-BD isomer is less inhibitory to P. polymyxa than the levo isomer.

Increase in levo-2,3-BD concentration decreases glucose utilization by P. polymyxa.