Factors influencing the potential use of Aliquat 336 for the in situ extraction of carboxylic acids from cultures of Pseudomonas putida

The use of extraction techniques to alleviate product inhibition in bioprocesses is one of a number of potential separation methods. However, the intimate contact of an organic phase with the broth implies that the organic components of this phase may be present in the aqueous phase at saturation levels. The quaternary amine Aliquat 336 (trioctyl/decylmethylammonium entity), dissolved in octan-1-ol showed no inhibition on the growth of Pseudomonas putida, at least with respect to molecular toxicity. Nevertheless, it is important to point out two main effects of Aliquat 336 associated with its ion exchange properties. It is able (1) to complex hydroxyl ions and therefore drastically lower the pH of the broth and (2) release its counter ion through these exchanges. Therefore, a strict control of the pH of the cultivation must be conducted, with the constraint that Ps. putida has an optimal pH growth of 7.4-7.5. The pH range tolerated by this strain is, however, between 5.0 and 9.0. In addition, the counter ion of Aliquat 336 needs to be carefully chosen and HSO4- should be preferred to Cl-.