Cell recycle and broth reuse fermentation with cross-flow filtration and ion-exchange resin

A novel integrated fermentation system in which cross-flow filtration was coupled to an anion-exchange resin column was developed to achieve biomass recycle and broth reuse for lactic acid fermentation. An anion-exchange resin column was employed to recover lactic acid from the spent broth. The effluent was diluted with fresh medium, supplemented with glucose and nutrients. Spent broth was reused for three consecutive biomass recycle fermentations with no significant decrease in fermentation performance. The fermentation system enabled simultaneously high productivity of lactic acid (average value 7.75 g dm^-3 h^-1 and total amount of lactic acid produced 85.21 g dm^-3 after 11 h fermentation), high productivity of cells (average value 2.00 g dm^-3 h^-1) and efficient utilization of medium (about 75% of the spent broth was reutilized). The system described may be applied to other organic fermentations subject to end-product inhibition.