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The application of bipolar electrodialysis (BPED) for the simultaneous removal of inhibitory acetate and pH control during E. coli fermentation was investigated. A two cell pair electrodialysis module, consisting of cation exchange, anion exchange and bipolar membranes with working area of 100 cm2 each, was integrated with a standard 7 l stirred tank bioreactor. Results showed that BPED was beneficial in terms of in situ removal of inhibitory acetate and a reduction in the amount NH4OH used for pH control. In batch and fed-batch BPED fermentations, base additions were decreased by up to 50% in both cases compared to electrodialysis (ED) fermentations with pH controlled at 6.7 ± 0.1. Consequently, the final biomass (34.2 g DCW l−1) and recombinant protein (5.5 g l−1) concentrations obtained were increased by up to 37 and 20%, respectively. [ABSTRACT FROM AUTHOR]

The efficiency of bipolar electrodialysis (BED) for the recovery of lactic acid from fermentation broth was evaluated. Three systems of BED (bipolar-anion, bipolar-cation and bipolar-anion-cation) at fixed voltage (20 V) were compared using a model solution of ammonium lactate (100 g l−1). Results showed that bipolar-anion (BED-anion) was the most beneficial in terms of lactate flux, current efficiency, energy consumption and recovery ratio. Consequently, BED-anion was used to purify lactic acid from fermentation broth which had been pre-treated with mono-polar electrodialysis (MED). The final lactic acid concentration and lactate flux obtained were 144 g l−1 and 393 g m−2 h−1, respectively. Using the two-step process (MED and BED-anion) the concentration of fermentation broth was increased by 33% and the total energy consumption was 2.76 kW h kg−1. [ABSTRACT FROM AUTHOR]