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1) OBT7 mutant was isolated by UV light-butanol tolerance from Clostridium saccharoperbutylacetonicm ATCC 13564 (N1-4 strain). The mutant produced 16.5 g/ℓ (1.4-fold increase) of n-butanol, 4.65 g/ℓ (1.5-fold increase) of acetone, and 21.5 g/ℓ of total solvent. It was suggested that clostridial bacteria producing n-butanol does not have a poor effect on misrepair via an error-prone pathway by UV light-butanol tolerance. 2) Compared to glucose fermentation, in mannitol fermentation, OBT7 mutant did not produce acetone and acetic acid. And the ratios of n-butanol and ethanol to total solvents increased by 10.3% and 10.5%, respectively, totalling 20.8%, while the ratio of acetone was decreased by 21.2%. Also the maximum ratio of n-butanol to total solvents reached 94.8%. These results indicated that oxidized compound (acetone, acetic acid, and butyric acid) was converted to the reduced compounds (n-butanol, and ethanol). Therefore, mannitol can be used to eliminate by-products of oxidized compound.
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