Abstract

A bacterium strain belonging to Microbacterium sp., isolated from oily sludge samples of Siri Island in the south of Iran, produced a strong, thermo stable microbial demulsifier (Y_x/s=0.663, Y_p/s=0.204, productivity=0.185 g L^-1 h^-1) on glucose as a sole carbon source supplemented with yeast extract. The optimum values of temperature, inoculum concentration, pH and culture age for microbial demulsifier production were 25°C, 10⁸ CFU mL^-1, 7 and 24 h, respectively. The maximum demulsification activity and the half-life value (t_1/2) of culture broth measured for a water-in-crude oil (W/CO) emulsion were 96.4% and 36 h at 80°C in flask. The demulsifier was purified to homogeneity using cold ethanol. For 4.33 mg mL^-1 of partially purified microbial demulsifier, the half-life value for the W/CO model emulsion was 3 h.

Key words: Biopolymer, demulsification, Microbacterium, demulsifier, petroleum emulsion, water-in-crude oil.