COMPARATIVE PHYSIOLOGY OF GEOSMIN PRODUCTION BY STREPTOMYCES-HALSTEDII AND ANABAENA SP

Geosmin and 2-methylisoborneol (MIB) are microbial metabolites that can cause earthy or musty off-flavors in aquatic food animals as well as seasonal taste and odor episodes in drinking water. This paper compares effects of selected environmental factors on biomass and geosmin production by the actinomycete Streptomyces halstedii and the cyanobacterium Anabaena sp., isolated from an aquaculture pond and from a source-water reservoir, respectively. For S. halstedii, optimal biomass production occurred at pH 6-7 and 30 degrees C, and optimal geosmin synthesis occurred at pH 9 and 35 degrees C. Low concentrations of both nitrate- and ammonium-nitrogen favored geosmin production, with higher concentrations stimulating biomass production. For Anabaena sp., optimal biomass production at 20 days occurred at 15 degrees C and a light intensity of 17 mu E/m(2)/s; optimal geosmin synthesis occurred at 20 degrees C and 17 mu E/m(2)/s. Chlorophyll a (chl a)/biomass varied inversely with light intensity. Maximal geosmin/biomass occurred at 20 degrees C (17 mu E/m(2)/s), and geosmin/chl a varied inversely with temperature. It was concluded that at 20 degrees C, increasing light intensity favors lower chl a and greater geosmin synthesis by Anabaena sp.; at 17 mu E/m(2)/s, increasing temperature stimulates chl a production (to 25 degrees C) but represses geosmin synthesis (above 20 degrees C).