Volatile hydrocarbon biodegradation by a mixed-bacterial culture during growth on crude oil

Volatile hydrocarbon biodegradation by a mixed-bacterial culture during gro wth on Bow River crude oil was investigated using solid phase microextracti on (SPME). Inoculum treatments were examined In relation to C-5-C-11 hydroc arbon degradation. Up to 1600 mg/l biomass (dry weight) was tested without achieving significant volatile hydrocarbon partitioning and affecting analy sis. Inoculum age rather than concentration had the most profound impact on biodegradation. When late log phase crude oil-grown inocula were used, C-5 -C-11 biodegradation reached 55-60%; methylcyclohexane and other branched c ompounds eluting before n-C-8 were recalcitrant. Increasing the late log in oculum concentration from 0.63 to 63 mg/l resulted in a twofold increase in degradation rate without improving the substrate range. Methylcyclohexane recalcitrance was correlated with reduced levels of hydrocarbon degrading b acteria and volatile hydrocarbon evaporation from the inoculum flasks. A de creased lag phase prior to degradation was observed when using early statio nary phase cultures as inocula and most compounds up to C-11, including met hylcyclohexane, were biodegraded.