Physiological Changes Occurring in the Cellular Membranes of Clostridium Acetobutylicum ATCC 824 and a Butanol-Tolerant Mutant During the Acetone-Butanol-Ethanol Fermentation
Baer, Shirley Haruko
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https://hdl.handle.net/2142/70099
Description
Title
Physiological Changes Occurring in the Cellular Membranes of Clostridium Acetobutylicum ATCC 824 and a Butanol-Tolerant Mutant During the Acetone-Butanol-Ethanol Fermentation
Author(s)
Baer, Shirley Haruko
Issue Date
1988
Department of Study
Food Science
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Microbiology
Abstract
The acetone-butanol-ethanol fermentation by Clostridium acetobutylicum is not able to compete economically with the petroleum methods, due to the premature termination of this fermentation from the butanol produced by the cell. It is known that alcohols disrupt the membrane structure and function, therefore it would be important to determine how butanol disrupts the membrane and what adaptative response(s) would be beneficial.
The effects of butanol challenge (0, 1.0, and 1.5%, vol/vol) and temperatures (22, 37, and 42$\sp\circ$C) on growth and membrane physiology of Clostridium acetobutylicum ATCC 824 and a butanol-tolerant derivative (SA-2) were examined. The specific growth rates of the SA-2 mutant were consistently higher than the parent strain at all temperatures studied. Although SA-2 demonstrated a 27% increase in butanol tolerance, the abilities to produce butanol and sporulate were diminished. In preliminary fatty acid determinations, unchallenged growth of the 824 strain into the stationary phase coincided with a gradual increase in the saturated/unsaturated (S/U) acyl chain ratio. The addition of 1.0 or 1.5% butanol to cells grown at 22 and 37$\sp\circ$C caused an immediate (within 30 min) dose response increase in the S/U ratio with little further change. Growth of the SA-2 into late-stationary phase at 22 and 37$\sp\circ$C coincided with a gradual increase of the S/U ratio which resulted in an overall greater increase in the S/U ratio for both unchallenged and challenged cells when compared to the 824 strain. Incorporation of exogenous 18:1 fatty acids did not improve tolerance in either strain. There were no obvious changes of the phospholipid headgroups in either strain when exposed to butanol.
Based on fluorescence depolarization and ESR data, 824 cell membranes become more fluid than SA-2 cell membranes when exposed to butanol.
Differences in colony morphology, granulose accumulation, and DNA content between the parent strain and SA-2 mutant were also observed.
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