Recovery of Rhamnolipids Produced by Pseudomonas aeruginosa Using Acidic Precipitation, Extraction, and Adsorption on Activated Carbon

Abstract

Biosurfactants are produced by microorganisms, especially those of the genus Pseudomonas. This study is concerned with the recovery of rhamnolipids produced by Pseudomonas aeruginosa P029-GVIIA, using molasses as substrate. A central compound design 2³ in triplicate at the central point was used to evaluate, the influence of the centrifugation time, the agitation speed, and the pH on the amount of rhamnolipids precipitated by HCl (2 N). A 2⁴ factorial design in triplicate at the central point was used to investigate the influence of the pH (3–10), temperature (30 to 50°C), the concentration of carbon (1–3% w/v), and the agitation speed (100–200 rpm) on the adsorption of rhamnolipids to activated carbon. The tests showed that the adsorption is governed particularly by the pH and the temperature, as well as by the temperature × pH interaction. A pseudo-first order kinetic model successfully fitted the data, showing that the adsorbent had the ability to adsorb approximately 17.16 mg of rhamnolipids/gram of activated carbon.

Keywords:

• activated carbon
• biosurfactant
• molasses
• Pseudomonas aeruginosa
• rhamnolipds

ACKNOWLEDGEMENTS

The authors thank CAPES and National Council of Research (CNPq) for their financial support.

Notes

*Centrifugation time (t) and centrifugation speed (A) refer to after acidification and overnight precipitation.

(T) – Temperature, (C _C ) – concentration of activated carbon, ω – agitation speed of the shaker.

CP – central point, M – mass of the precipitate in grams. The independent variables of centrifugation time (t), centrifugation speed (A) and pH are shown for the factorial portion (codified values −1 and 1), in triplicate at CP (0) and for the axial portion (with codified values of α = ±1,682).