Microbially Derived Off-Flavor from Geosmin and 2-Methylisoborneol: Sources and Remediation - Reviews of Environmental Contamination and Toxicology - page 9

The first reports of geosmin production by Anabaena circinalis, Anabaena laxa , and
Symploca muscorum were published by Henley (1970), Rashash et al. (1996), and
Medsker et al. (1968), respectively. Many species of blue-green algae and actinomyc-
etes can produce geosmin, but in catfish ponds, the main geosmin producers are species
of the blue-green alga Anabaena , followed by Aphanizomenon or Lyngbya (van der
Ploeg et al. 1992; Schrader and Blevins 1993). A geosmin-producing Oscillatoria strain
and one Anabaena species were isolated from drinking water supplies in California
(Izaguirre et al. 1982). Geosmin- and MIB-producing cyanobacteria found in the U.S.
also occur in other countries. In Australia, Anabaena circinalis , which produces geos-
min along with saxitoxin, is a major problem, causing the deaths of animals (Negri et
al. 1995). This species is also reported from South African reservoirs (Wnorowski and
Scott 1992). Oscillatoria splendida (now called Geitlerinema splendidum ) is a common
geosmin producer widespread throughout the Northern Hemisphere.
Nielsen et al. (2006) found that bacterial groups within Actinobacteria produce
the compounds geosmin and MIB, which lower the quality of surface water when
used for drinking. Results indicate that combined microautoradiography and cata-
lyzed reporter deposition (CARD-FISH) may serve as an effective tool when study-
ing identity and activity of microorganisms within freshwater environments
(Nielsen et al. 2006). Klausen et al. (2005) attributed the occurrence of the geosmin
and MIB in freshwater environments to Actinobacteria, most of them belonging to
the genus Streptomyces (Schrader and Blevins 1993; Zaitlin et al. 2003; Zaitlin and
Watson 2006). The new species Penicillium discolor , frequently isolated from nuts,
vegetables and cheese, also produces the moldy-smelling compounds geosmin and
MIB (Frisvad et al. 1997). A correlation between the occurrence of geosmin, argos-
min and heptadec- cis -5-ene and the presence of the cyanobacterium Aphanizomenon
gracile was observed by Jüttner (1984). These compounds were present in spring
and autumn, when A. gracile also occurred in the lake, but were not detected in
summer, when the organism was absent.
A Phormidium sp. reported by Izaguirre (1992) was rare among cyanobacteria
in that it could produce both MIB and geosmin (see Table 4). Five other cyanobac-
teria with this property have been reported: three strains in Norway (Berglind et al.
1983b), one in Japan (Matsumoto and Tsuchiya 1988), and one in Taiwan (Wu and
Jüttner 1988). Schrader and Dennis (2005) reported that geosmin and MIB were
implicated for earthy and musty off-flavors, respectively, in farm-raised channel
catfish ( Ictalurus punctatus ) in the Southeastern U.S. MIB-producing cyanobacte-
rium ( Oscillatoria perornata ) is present in catfish ponds in both Mississippi and
Alabama Blackland Prairie (MABP), whereas geosmin was found to be more prev-
alent in catfish ponds in the MABP region than West Mississippi.

IV Biosynthesis of Geosmin

Bentley and Meganathan (1981) used radiogas chromatography to investigate bio-
synthesis of geosmin, the characteristic odoriferous constituent of Streptomyces
species. Based on the incorporation of acetate into geosmin by strains of S. antibioticus ,