10.2.1 Organisms

Microbial butanol synthesis was first noticed by famous French scientist Louis Pasteur in 1862 (Pasteur, 1862). While his organism Vibrion butyrique presumably represented a mixed culture, a pure culture was isolated a few years later by Albert Fitz (Fitz 1876, 1877, 1878, 1882). Around the turn of the twentieth century, further butanol-producing bacteria were isolated by many other scientists, amongst them are Martinus Beijerinck and Sergei Winogradsky. Probably, all of these isolates were members of the genus Clostridium, a term that was only used as a morphological description (from Greek kloster = small spindle) at that time. However, most of these strains were lost over the years (Durre, 2001; Durre, 2005a; Durre and Bahl, 1996).

In 1913, Charles Weizmann isolated a strain, which produced significantly higher butanol yields (Weizmann, 1915) and later became known as Clostridium acetobutylicum (McCoy et al., 1926). In succession, many similar strains were isolated and also designated as C. acetobutylicum. Only at the beginning of the 1990s, it was discovered that actually four different species (C. acetobutylicum, Clostridium beijerinckii, Clostridium saccharobutylicum and Clostridium saccharoperbutylacetonicum) were industrially used (Jones and Keis, 1995; Keis et al., 2001).

Other Clostridium species (see Table 10.1 and Fig. 10.1) are able to form minor amounts of butanol as well (Durre, 2005a; Durre and Bahl, 1996). However, aside from this genus, only Thermoanaerobacterium thermosaccharolyticum (formerly Clostridium thermosaccharolyticum; Collins et al., 1994), Butyribacterium methylotrophicum and the archeon Hyperthermus butylicus are known to produce 1-butanol (see Table 10.1 and Fig. 10.1). While the respective mechanisms in these organisms are still unclear (Brugger et al., 2007; Grethlein et al., 1991), butanol formation in clostridia has already been investigated extensively.