4. DiscussionSurvival of microorganisms in petroleum hydrocarbonsmedium after their inoculation is a key deciding factor inthe rate of biodegradation of hydrocarbons either in soil orin liquid phase (Ramos et al., 1991). Since all the bacteria inthe present study were isolated from a petroleum contaminatedsoil sample, they survived and adopted the oilcontaminatedsoil/liquid environment very easily as alsoreported by other authors (Rahman et al., 2003; Sugiuraet al., 1997). This was evident from the signiWcant increase(p<0.01) in the population of B. subtilis and P. aeruginosain soil as compared to control. However, higher growth rate(p<0.05) of Pseudomonas strains compared to Bacillusstrain might be related to higher breakdown and utilizationof petroleum hydrocarbons by former strains. Besides, thenecessity for seeding with hydrocarbon degrading bacteriamight have arisen from the fact that indigenous microbes ofsoil were not eYcient degraders of a wide range of complexcompounds of crude petroleum-oil and therefore, introductionof eYcient hydrocarbon degraders would be essentialin order to eVectively degrade all of the hydrocarbons in acomplex petroleum mixture (Atlas, 1977). Since the supplementationof glucose as co-carbon source enhanced the rate of biodegradation of PAH by bacterial strains used in thisstudy (Das and Mukherjee, in press), glucose was added inthe oil-contaminated soil after a regular interval to increasethe rate of biodegradation of TPH by the seeded bacteria.However, present results were in contradiction to report ofChhatre et al. (1996) describing addition of nutrients in thesoil was unlikely to have dramatic eVect on the microbialdegradation of crude oil.
การแปล กรุณารอสักครู่..
