Purification and concentration of a rhamnolipid biosurfactant produced by Pseudomonas aeruginosa SP4 using foam fractionation.

Pseudomonasaeruginosa SP4 was cultivated to produce a rhamnolipid biosurfactant from a nutrient broth with palm oil. The foam fractionation technique in batch mode was used for the recovery of the excreted biosurfactant from the free-cell culture medium. The effects of air flow rate, initial foam height, the pore size of the sintered glass disk, initial liquid volume, and operation time on the process performance were studied. The results showed that the operating conditions were optimized at an air flow rate of 30 ml/min, an initial foam height of 60 cm, a pore size of the sintered glass disk in the range of 160-250 microm (No. 0), an initial liquid volume of 25 ml, and an operation time of 4 h, providing a biosurfactant recovery of 97% and an enrichment ratio of 4. The HPLC results also indicated that the rhamnolipid was concentrated by using the foam fractionation technique.