title: Formic acid triggers the "Acid Crash" of acetone-butanol-ethanol fermentation by Clostridium acetobutylicum.
abstract: Solvent production by Clostridium acetobutylicum collapses when cells are grown in pH-uncontrolled glucose medium, the so-called "acid crash" phenomenon. It is generally accepted that the fast accumulation of acetic acid and butyric acid triggers the acid crash. We found that addition of 1 mM formic acid into corn mash medium could trigger acid crash, suggesting that formic acid might be related to acid crash. When it was grown in pH-uncontrolled glucose medium or glucose-rich medium, C. acetobutylicum DSM 1731 containing the empty plasmid pIMP1 failed to produce solvents and was found to accumulate 0.5 to 1.24 mM formic acid intracellularly. In contrast, recombinant strain DSM 1731 with formate dehydrogenase activity did not accumulate formic acid intracellularly and could produce solvent as usual. We therefore conclude that the accumulation of formic acid, rather than acetic acid and butyric acid, is responsible for the acid crash of acetone-butanol-ethanol fermentation.
authors.affiliation: Institute of Microbiology, Chinese Academy of Sciences, No. 1 West Beichen Road, Chaoyang District, Beijing 100101, China.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Wang
authors.forename: Yanping
authors.initials: Y
authors.lastname: Zhang
authors.forename: Hongjun
authors.initials: H
authors.lastname: Dong
authors.forename: Shaoming
authors.initials: S
authors.lastname: Mao
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhu
authors.forename: Runjiang
authors.initials: R
authors.lastname: Wang
authors.forename: Guodong
authors.initials: G
authors.lastname: Luan
authors.forename: Yin
authors.initials: Y
authors.lastname: Li
mesh_terms: D019342:Acetic Acid / Q000633:toxicity; D000096:Acetone / Q000378:metabolism*; D000440:Butanols / Q000378:metabolism*; D020148:Butyric Acid / Q000633:toxicity; D046969:Clostridium acetobutylicum / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005561:Formates / Q000633:toxicity*; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D010957:Plasmids; D003313:Zea mays / Q000378:metabolism
chemical_list: D000440:Butanols; D003470:Culture Media; D005561:Formates; C030544:formic acid; D020148:Butyric Acid; D000096:Acetone; D000431:Ethanol; D005947:Glucose; D019342:Acetic Acid