Comparative investigations of growth and solvent formation in 'Clostridiumsaccharoperbutylacetonicum' DSM 2152 and Clostridium acetobutylicum DSM 792

The butanol and acetone-producing strain DSM 2152, invalidly described as ' Clostridium saccharoperbutylacetonicum' is compared with the type strain C. acetobutylicum, DSM 792, with respect to solvent and acid formation at var ying pH values and growth rates. Batch cultures, product-limited chemostat and pH-auxostat cultures were used for characterization. Under all conditio ns strain DSM 2152 produced much lower amounts of butyric and acetic acids than the type strain. The pH optimum for solvent formation was higher, ie 5 .5 instead of 4.5, Solvent formation occurred at higher dilution rates, but below 0.1 h(-1) a lower solvent concentration was obtained, indicating tha t acid production was too low to provide a sufficient amount for acetone fo rmation. The results are discussed in the light of recent publications on t he taxonomy of butanol-acetone producing clostridia using 16S rRNA sequence analysis and other nucleic acid data, The presently suggested 'phylogeneti c' classification of the collective species, C. acetobutylicum, is also ref lected in the fermentation characteristics.