Biodegradation of fuel oxygenates by sol–gel immobilized bacteria Aquincola tertiaricarbonis L108

The development of long-term storable biofilters containing bacteria which are capable to degrade recalcitrant environmental compounds like the fuel oxygenates methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) is of special interest for the treatment of contaminated water. Fuel oxygenates have been proven to be more persistent to biodegradation than other gasoline components. Only a few microorganisms, e.g. Aquincola tertiaricarbonis L108, are capable to biodegrade these substances. In order to develop highly efficient and long-term stable biocomposite materials for bioremediation, the applicability of sol–gel matrices for the immobilization of A. tertiaricarbonis was tested. Two different sol–gel immobilization techniques were used: (A) the immobilization within ceramic-like shapes by using the freeze-gelation technique and (B) sol–gel coatings on an inert, porous material. For comparison, the widely used alginate-bead immobilization technique has been applied. The embedding of A. tertiaricarbonis within freeze-gelation composites (method A) proved to be not applicable because this strain was too sensitive regarding the applied freezing and drying conditions even though cell-protecting additives were added. In contrast, A. tertiaricarbonis immobilized on porous expanded clay pellets (method B) could be stored under humid atmosphere at least for a time of 8 months without a significant reduction of their metabolic activity.