Ability of Bacillus to Degrade Geosmin

Abstract

The ability of Bacillus strains to degrade geosmin, a musty off-flavor component present in superficial waters, led some authors to postulate the existence of a Bacillus exoenzyme: the “geosminase”. Such an enzyme, as an immobilized form onto a granular material, would be of a great interest to remove geosmin from water. This prospect prompted us to look for geosminase in Bacillus cultures. An aqueous solution of pure geosmin was added to Bacillus culture supernatants from exponential or stationary phases, and to a whole culture induced for 24 hours with 0.06 ppm of geosmin. Geosmin was determinated by GLC as a function of incubation time. No evidence of enzymatic activity was obtained, but an important adsorption of geosmin onto glass vessels was observed at neutral pH (6.7–7.5). Geosmin was recovered from glass by elution with methanol. Thus great care must be taken before assuming a biological origin to geosmin disappearance from superficial waters. However, preliminary results indicate that a “true” geosminase can be detected in Actinomycete lysates. The characterization and the purification of this enzyme are actually in progress.