Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/18/2009
Publication Date: 7/4/2009
Citation: Eaton, R.W., Sandusky, P. 2009. Biotransformation of geosmin by terpene-degrading bacteria. Applied and Environmental Microbiology. 21:71-79. Interpretive Summary: Geosmin, produced by various micro-organisms in the environment, is one of a few chemicals that separately or together are responsible for the characteristic earthy smell of soil. It is also often responsible for giving farm-raised catfish an earthy off-flavor. While it can sometimes be eliminated from catfish prior to harvesting by moving the fish to clean water, this often results in harvest delays and increased costs with significant reductions in profit for the farmer. Since it is not currently possible to prevent geosmin-producing cyanobacterial blooms from occurring in ponds and reservoirs, a practical solution to the geosmin problem might be to remove the chemical by treatment with geosmin-degrading bacteria. In this paper, two bacteria that are able to convert geosmin to oxidized products are described. The camphor-degrading Rhodococcus wratislaviensis DLC-cam and -terpinene-degrading Pseudomonas sp. SBR3-tpnb each rapidly transform geosmin to mixtures of products, primarily keto-geosmins. It is expected that these and other bacterial strains being investigated at this laboratory can be employed to eliminate geosmin from catfish aquaculture.
Technical Abstract: Two terpene-degrading bacteria that are able to transform geosmin have been identified. Pseudomonas sp. SBR3-tpnb, isolated on -terpinene, converts geosmin to several products; the major products are keto-geosmins. This geosmin transformation ability is inducible by -terpinene. Rhodococcus wratislaviensis DLC-cam, isolated on D-camphor, also converts geosmin to several oxidation products, primarily keto-geosmins that differ from those produced by strain SBR3-tpnb. This conversion appears to be inducible by (+/-)-geosmin. Rigorous NMR identification of the products has been complicated by the use of enantiomers as substrates, essentially doubling the number of difficult-to-separate metabolites.