Abstract.
The thermophilic Bacillus strain BS119 was selected for this study to demonstrate the long term performance of lactic acid production and simultaneous pre-purification. Integrated continuous cell recycle cultivation using ultra-filtration membrane bioreactor (MBR) systems was investigated. The permeate from the MBR was routed to an on-line electrodialysis (ED) to recover, pre-purify and concentrate lactate. The cultivation and ED was operated at 60°C for more than 1,000 h at a pH of 6.5. At lower dilution rate (0.02 h–1), lactate concentration reached a maximum of 55 g l–1 with clearly lower residual glucose levels. At 0.04 h–1, lactate concentration was significantly lower at 35 g l–1. Maximal volumetric productivities of 1.38 g l–1 h–1 were achieved. Under stable conditions, lactic acid yield on consumed glucose appeared stable at around 80%. It could be demonstrated that the addition of supplements like yeast extract and peptone severely influences product formation. Integration of mono-polar ED with the MBR systems yields lactate solutions with concentrations of up to 115 g l–1. Because of the low substrate feed concentrations (less than 50 g l–1), lactate flux was rather poor, reaching a low maximum of 140 g m–2 h–1; nevertheless, stack energy consumption was positive with an average of 0.49 kWh kg–1 lactate.
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Danner, .H., Madzingaidzo, .L., Thomasser, .C. et al. Thermophilic production of lactic acid using integrated membrane bioreactor systems coupled with monopolar electrodialysis. Appl Microbiol Biotechnol 59, 160–169 (2002). https://doi.org/10.1007/s00253-002-0998-4
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DOI: https://doi.org/10.1007/s00253-002-0998-4