Fermentation of rhamnolipids from waste frying oil for application in cleaning oil sludge

A candidate strain for producing biosurfactants was isolated from local oil-polluted environment which was identified as P aeruginosa and named as P aeruginosa ZJU u1. The maximum productivity of rhamnolipids by P aeruginosa ZJU u1 was 12.54 g/L after fermentation 120 h in shaking flask when the waste frying oil was the sole carbon source. The culture broth of P aeruginosa ZJU u1 could decrease the surface tension of the solution to 37 × 10-3 N/m with a critical micelle concentration (CMC) of 63.3 mg/L. The results showed that the fermentation broth could increase the efficiency of oil tank cleaning and the oil recovery from the oil-tank sludge.