Production of Rhamnolipid Biosurfactant from Waste Cooking Oil Using Pseudomonas putida in a Batch Reactor

Surfactants are surface-active chemicals with a world production of more than 15 million tons per annum. The majority of surfactants in the market are produced from petrochemical sources, and thus they are termed synthetic surfactants. With the increased environmental consideration from consumers and producers, increased interest is moving toward biologically derived surfactants (biosurfactants). In this study, waste cooking oil was utilized as a carbon source in rhamnolipid production in a batch reactor using Pseudomonas putida, a nonpathogenic microorganism, as a way of improving the uneconomical production of rhamnolipid, a biosurfactant using waste materials. Two nitrogen sources, ammonium nitrate and urea, were used and varied to investigate their effects on rhamnolipid production. The waste cooking oil consumption by the microbe was quantified with the use of a carbon oxygen demand (COD) kit. The activity of the biosurfactant was verified by determining surface tension using the capillary tube method. Results showed that P. putida was capable of using waste cooking oil and both nitrogen sources to produce rhamnolipid with higher cell growth obtained for ammonium nitrate. It was also shown that the utilization of ammonium nitrate as a nitrogen source improved the growth of Pseudomonas putida at an initial waste cooking oil concentration of 6%, while the use of urea as a nitrogen source yielded a higher production of rhamnolipid of 8.8 g/L after 96 h. Therefore, waste cooking oil was successfully utilized in this study as a waste substrate for rhamnolipid production using Pseudomonas putida.