Enhancement of hydrocarbon degradation using biosurfactants from Rhodococcus species in a membrane reactor system
Abstract
Bacterial degradation of hydrocarbons has achieved greater prominence after the
discovery of organisms that have been reported to degrade a host of recalcitrant
compounds. The ability of bacteria to degrade hydrocarbons is a viable alternative to
other energy intensive clean up options. One of these degradative pathways is through
the production of biosurfactants, which have exhibited greater advantages than their
chemical counterparts. In this work, two strains of the robust Rhodococcus genus
namely Rhodococcus opacus and Rhodococcus ruber have been tested for their ability
to degrade n-hexadecane. In order to elicit the maximum production of surfactants, the
optimisation of the growth medium with respect to nitrogen source, temperature and
rotation speed was carried out. The Phenol-Sulphuric acid assay was employed to
quantify the amount of surfactant produced. Biosurfactant efficacy was then determined
by measuring the emulsification activity, adhesion to hydrocarbons and reduction in
surface tension. Two different mixed-culture reactors were utilized whereby one
involved use of a conventional 3L automated batch reactor and another where a
specially designed membrane reactor, in which by the use of membrane partitions,
enables the two strains of bacteria to be physically separated. From the experiments
carried out there is clear indication that using a membrane reactor would be better suited
for mixed culture reactor systems. Mixed culture membrane reactors are promising in
the field of bioremediation.