Process optimization for the production of rhamnolipid and formation of biofilm by Pseudomonas aeruginosa CPCL on polypropylene

The effect of rhamnolipid during the formation of initial biofilm (48 h) by Pseudomonas aeruginosa CPCL on polypropylene surface was studied. This strain was isolated from a petroleum contaminated soil and it produces a mixture of rhamnolipids. The nutritional and environmental conditions necessary for optimal production of rhamnolipid, attachment of rhamnolipid and formation of thicker biofilm on the polypropylene surface were found to be different from one another. Comparatively lower pH and temperature, higher concentration of ammonium chloride and rotation velocity of the shaker were required for the biofilm formation and the attachment of rhamnolipid on the polypropylene surface. Screening design showed that the extent of viable cells and rhamnolipid attached to the polypropylene surface was positively correlated (r = 0.474; p < 0.01). However, central composite design did not show any such relationship, possibly because of the different experimental ranges used in central composite design. There were considerable variations in the thickness and spatial arrangement of biofilms grown under these three different optimized conditions. Higher substratum coverage and thicker biofilm were observed under the condition optimized for biofilm formation when compared to the other two conditions. This study is essential since P. aeruginosa biofilms are found to have implication in bioremediation of recalcitrant pollutants. (C) 2011 Elsevier B.V. All rights reserved.