Biochemical and Ecological Control of Geosmin and 2-Methylisoborneol in Source Waters

Abstract

2The majority of all biologically caused taste-and-odor outbreaks in drinking water characterized worldwide are caused by microbial production of (Ϫ)-geosmin [(Ϫ)-(4S,4aS,8aR)-4,8a-dimethyloctahydronaphthalen-4a-ol] and (Ϫ)-2-methylisoborneol (2-MIB) {(1R-exo)-1,2,7,7-tetramethylbicyclo[2.2.1]heptan-2-ol}. Since they were first identified in the early 1960s, these two earthy-muddy-smelling metabolites have been the focus of considerable research, which has collectively produced over 400 scientific articles, reports, websites, and conference proceedings. Yet despite this substantial body of knowledge, geosmin and 2-MIB remain poorly understood throughout much of the water industry, and misconceptions which impede the prediction, treatment, and control of these volatile organic compounds (VOCs) persist. This paper reviews salient aspects of our current knowledge on the sources and properties of geosmin and 2-MIB which are essential to understanding and managing drinking water malodors. In particular, we highlight some key factors regulating the storage and release of these compounds by cells. These important factors are often overlooked and may contribute to some of the apparent ambiguity of many taste-and-odor outbreaks.

A systematic study on spatial and seasonal patterns of eight taste and odor compounds with relation to various biotic and abiotic parameters in Gonghu Bay of Lake Taihu, China

“…Similarly, Dzialowski et al (2009) found that cyanobacterial biovolume is not a consistent predictor of dissolved geosmin, and Durrerl et al (1999) indicated that correlations between a particular taxon and particle-bound geosmin cannot be expected to occur in any instance in natural waters. On the contrary, a few researchers observed positive correlation between geosmin and cyanobacterial biovolume (Jüttner and Watson, 2007;Sugiura et al, 2004). Li et al (2007) suggested that dissolved odorous compounds are affected by various factors, such as rate of odor production by algal cells, biodegradation by microbes, photolysis by sunlight, absorption by particles, disturbance by wave and volatilisation of odorous compounds themselves.…”

Contribution of Streptomyces in sediment to earthy odor in the overlying water in Xionghe Reservoir, China

“…There have been numerous studies on odorous compounds in drinking water, water products, and the surface waters of lakes, reservoirs and rivers; however, few of these studies have investigated geosmin and 2-MIB in the benthic environment or in the surrounded biofilms and investigated the effect of the benthic production of these compounds on water bodies and water products (Jü ttner and Watson, 2007).…”

Dynamics and polyphasic characterization of odor-producing cyanobacterium Tychonema bourrellyi from Lake Erhai, China

“…Three strains of T. bourrellyi isolated from Lake Erhai were shown to produce both β-ionone and geosmin in the present study. Although no direct evidence demonstrated the health risks of geosmin and MIB for humans or aquatic animals (Dionigi et al 1993;Jüttner and Watson 2007), these two mustyearthy monoterpene and sesquiterpene metabolites have been regarded as the cause of frequent taste and odor incidents in water supplies, because of their strong earthy smell and extraordinarily low sensory threshold as 2-20 ng L −1 for humans (Cook et al 2001;Izaguirre and Taylor 2004). Therefore, the presence of T. bourrellyi, the geosmin producer, implied a potential off-flavor risk for water quality around Lake Erhai.…”

“…This species was reported to form exceptional Oscillatoria-like blooms (Revaclier 1978;Berglind et al 1983;Ganf et al 1991). Furthermore, Responsible editor: Philippe Garrigues T. bourrellyi also produces geosmin or β-ionone (Berglind et al 1983;Jüttner and Watson 2007;Shao et al 2013), exhibiting potential harmful impact. T. bourrellyi is one of the three formally accepted species of the genus Tychonema in the latest edition of Oscillatoriales taxonomy by Komárek and Anagnostidis (2005).…”