Adsorption Characteristics of Polyvinylpyridine and Activated Carbon for Lactic Acid Recovery from Fermentation of Lactobacillus Delbrueckii

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Fall 1998


Polyvinylpyridine (PVP) and activated carbon were examined for the adsorption characteristics pertinent to their application in lactic acid fermentation. For PVP the linear adsorption constant, Kad , was between 0.7 and 1.0 for an equilibrium pH range of 3 to 9. The pH was adjusted by acid/base addition, similar to pH control in fermentation. The values of Kad> in the pH-adjusted systems were much lower than that reported for pure lactic acid solutions, i.e., about 9.7. Furthermore, no clear effect of pH was observed. These are attributed mainly to the competition of anions (Cl∼ and lactate) for the adsorption sites of protonated pyridinal N. Its adsorption capacity was also found to decrease with the base regeneration (by about 14% each time) after being contacted with the culture broth. These limit its potential application in lactic acid fermentation. Activated carbon was much more effective in lactic acid/lactate adsorption than PVP. At pH 5.5 (optimal for fermentation), the value of Kad of activated carbon was about 7. The adsorption further favored lower pH under acid (HC1) addition. Activated carbon has been reported to adsorb glucose. However, the presence of glucose in 0–70 g/L was found in this study to have an insignificant effect on lactate adsorption. Cells of Lactobacillus delbrueckii also adsorbed rapidly on activated carbon. This cell adsorption had a negative effect on lactate adsorption.



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