Induction and development of the oil emulsifying system in an alkane oxidizing Rhodococcus species

The physiological criteria for the development of crude oil emulsifying act ivity in a Rhodococcus species isolated from sea water was investigated. Th e bacterium was used as a model organism and all experiments were performed in shake flasks at 30 degrees C. The development of emulsifying activity w as inducible, but only under conditions of cell growth. A test was develope d for assessing the ability of different chemical compounds to induce the c rude oil emulsifying activity in acetate pre-grown cells, and a comprehensi ve survey of possible inducers carried out. The compounds Chat gave excelle nt or good emulsification in the test assay included n-alkanes (C-11 to C-1 8), pristane, 1-decene, fatty alcohols (C-14 to C-18), the fatty aldehydes decanal and dodecanal, some unsaturated fatty acids and some oils containin g glycerol esters of unsaturated fatty acids. All these compounds also serv ed as sole carbon and energy sources. Alkanes and fatty acids behaving as s olids at 30 degrees C did not function as inducers in the assay. Heptamethy lnonane served as a moderate inducer, but not as a growth substrate. The in ducers had to be present in the concentration range of 0.01 to 0.05% (w/v)i n order to give a detectable emulsion under the conditions of the assay. The development of the emulsifying activity, hypothesised to comprise compo unds from the hydrophobic cell surface, is suggested to be coordinated with new cell wall synthesis.