The de-flocculating of the flocculating yeast SPSC01 under chemostat conditions was monitored with the focused beam reflectance measurement system (FBRM).When the medium containing 50 g8226;L-1 glucose

supplemented with 4 g8226;L-1 yeast extract and 3 g8226;L-1 peptone was fed at the dilution rate of 0.12 h-1

the size of the yeast flocs started to decrease in 15 days

indicating the occurrence of de-flocculating of the culture system.Batch culture and fermentation demonstrated that the free yeast cells de-flocculated from the yeast flocs grew faster but less tolerant to ethanol inhibition

making the chemostat culture system more favorable for them to grow and overtake the yeast flocs with extension of the culture period.A dynamic model was developed to simulate this de-flocculating process and the impact of de-flocculating probability

dilution rate

growth kinetic parameters

and a bioreactor operation model was further analyzed.It was expected that the improvement of the retention of the yeast flocs within the bioreactor could effectively prevent the de-flocculating from occurring

which was validated by installing a baffle within the bioreactor to retain the yeast flocs.