J. Gen. Appl. Microbiol., 51, 105–113 (2005)

Conjugated linoleic acid (CLA) has recently attracted considerable attention as a health-promoting substance. For example, CLA has been reported to prevent carcinogenesis (Pariza and Hargraves, 1985), atherosclerosis (Nicolosi et al., 1997), and tumorigenesis (Ha et al., 1990; Ip et al., 1991), to improve hyperinsulinemia (Houseknecht et al., 1998), and to modulate immune activity (Cook et al., 1993; Miller et al., 1994). Furthermore, CLA has been shown to reduce body fat to muscle mass ratio (Chin et al., 1992) and alter the ratio of low density lipoprotein to high-density lipoprotein cholesterol (Lee et al., 1994). As many as 16 CLA isomers are known to be produced by alkaline isomerization of linoleic acid (LA) (Nichols et al., 1951; Wedekind et al., 1988). Of these, the cis-9, trans-11 (c9, t11) and the t10, c12 configurations are shown to have the bioactivity described above (Rainio et al., 2001). The most important natural source of CLA is dairy products, which contain c9, t11CLA predominantly (Rainio et al., 2001). A new strain of Butyrivibrio fibrisolvens that has high ability to isomerize linoleic acid to conjugated linoleic acid