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.