Process development and optimisation of lactic acid purification using electrodialysis.
Cell free sodium lactate solutions were subjected to purification based on mono- and bi-polar electrodialysis. Lactate concentration in the product stream increased to a maximum of 15% during mono-polar electrodialysis. Stack energy consumption averaged 0.6 kW h kg(-1) lactate transported at current efficiencies in the 90% range. Under optimum feed concentration (125 g l(-1)) and process conditions (auto-current mode with conductivity setpoints of minimum 5 and maximum 40 mS cm(-1)), lactate flux reached 300 g m(-2) h(-1) and water flux were low for mono-polar electrodialysis averaging 0.3 kg H(2)O per M lactate transported. Glucose in the concentrate stream solutions was reduced to < 2 g l(-1). Acetate impurities enriched from about 0.5 g l(-1) in the feed stream to 1.5 g l(-1) in the concentrate stream solutions. After mono-polar electrodialysis, the concentrated sodium lactate solutions were further purified using bi-polar electrodialysis. Water transport during bi-polar electrodialysis reached figures of 0.070 - 0.222 kg H(2)O per M lactate. Free lactic acid concentration reached 16% with lactate flux of up to 300 g m(-2) h(-1). Stack energy consumption ranged from 0.6 to 1 kW h per kg lactate. Under optimised process conditions current efficiency during bi-polar electrodialysis was consistently around 90%. Glucose was further reduced from 2 to <1 g l(-1) in the free lactic acid solution. Acetic acid impurity remained at around 1 g l(-1). Significant reduction in colour and minerals in the product streams was observed during electrodialysis purification.
Madzingaidzo
L
L
Department of Environmental Biotechnology, Institute for Agro-biotechnology (IFA-Tulln), Konrad Lorenz Strasse 20, A-3430, Tulln, Austria.
Danner
H
H
Braun
R
R
D019149:Bioreactors; D003956:Dialysis / Q000379:methods*; D004563:Electrochemistry / Q000379:methods*; D005285:Fermentation; D019344:Lactic Acid / Q000032:analysis / Q000302:isolation & purification*; D008953:Models, Anatomic; D019354:Sodium Lactate / Q000302:isolation & purification; D014867:Water / Q000737:chemistry
D014867:Water; D019344:Lactic Acid; D019354:Sodium Lactate