Bioenhancement of soil microorganisms in natural surfactant solutions .2. Anaerobic

Natural surfactant solutions obtained from fruit pericarps of Sapindus mukorossi are shown to solubilize significant quantities of hydrophobic organic compounds and mobilize them from soil matrix. It is very crucial to determine the fate of surfactants employed for soil flushing in the subsurface and also in the effluent recovered. This paper appraises the bioenhancement of soil microorganisms in natural surfactant solutions under anaerobic conditions. Sealed 125 ml serum bottles are used for developing the anaerobic cultures. The cultures are maintained in anoxic conditions by degassing and filling the bottles with nitrogen. Three concentrations of natural surfactant 0.1, 1 and 2% and two different nutrient media, basal salt media (BSM) and heterotrophic media are used in the studies. Natural surfactant solutions can serve as both carbon and energy source for anaerobic microorganisms and also degrade to considerable extent. The growth curves for anaerobic cultures followed similar trends as those for aerobic cultures reported in an earlier paper. Addition of BSM to cultures increased the growth significantly. However, heterotrophic media amended cultures showed only an increased initial growth rate. The microbial growth increased significantly when the surfactant concentration was increased from 0.1 to 2% by weight. The results suggest that natural surfactant can readily degrade under anaerobic conditions and needs to be studied further in the presence of soils and sediments.