BROTH RECYCLE IN A YEAST FERMENTATION

Fermentation is a water-intensive process requiring treatment of large amounts of effluent broth. It is desirable to increase the ratio of p roduct produced to the volume of effluent by minimizing the discharge of effluent from the fermentation process. A study of recycling spent fermentation broth for the subsequent fermentation was carried out wit h Apiotrichum curvatum, an oleaginous yeast, as the working culture. S pent broth from a defined medium was recycled to replace as much as 75 % of the water and salts for subsequent batches and this was repeated for seven sequential batches without affecting cell mass and lipid pro duction. A 64% volume reduction of wastewater was achieved in this man ner. However, when using whey permeate as the medium, lipid production dropped after three consecutive recycle operations at 50% recycle, an d after two consecutive recycle operations at 75% and 100% recycle. Ac cumulation of ions in the broth appeared to be responsible for the inh ibition. An ion exchange step was able to eliminate the ion buildup an d restore fermentation performance. (C) 1994 John Wiley and Sons, Inc.