Ethanol production by thermophilic bacteria: biochemical basis for ethanol and hydrogen tolerance in Clostridium thermohydrosulfuricum
The metabolic and enzymatic bases for growth tolerance to ethanol (4%) and H/sub 2/ (2 atm (1 atm = 101.29 kPa)) fermentation products in Clostridium thermohydrosulfuricum were compared in a sensitive wild-type strain and an insensitive alcohol-adapted strain. In the wild-type strain, ethanol (4%) and H/sub 2/ (2 atm) inhibited glucose but not pyruvate fermentation parameters (growth and end product formation). Inhibition of glucose fermentation by ethanol (4%) in the wild-type strain was reversed by addition of acetone (1%), which lowered H/sub 2/ and ethanol production while increasing isopropanol and acetate production. Pulsing cells grown in continuous culture on glucose with 5% ethanol or 1 atm of H/sub 2/ significantly raised the NADH/NAD ratio in the wild-type strain but not in the alcohol-adapted strain. Analysis of key oxidoreductases demonstrated that the alcohol-adapted strain lacked detectable levels of reduced ferredoxin-linked NAD reductase and NAD-linked alcohol dehydrogenase activities which are present in the wild-type strain. Differences in the glucose fermentation product ratios of the two strains were related to differences in lactate dehydrogenase and hydrogenase levels and sensitivity of glyceraldehyde 3-phosphate dehydrogenase activity to NADH inhibition. A biochemical model is proposed which describes a common enzymatic mechanism for growth tolerance of thermoanaerobes to moderate concentrations of both ethanol and hydrogen.
- Research Organization:
- Michigan Biotechnology Institute, Lansing (USA)
- OSTI ID:
- 6765379
- Journal Information:
- J. Bacteriol.; (United States), Vol. 170:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CLOSTRIDIUM
GROWTH
SENSITIVITY
ETHANOL
TOXICITY
HYDROGEN
ENZYME ACTIVITY
OXIDOREDUCTASES
THERMOPHILIC CONDITIONS
TOLERANCE
ALCOHOLS
BACTERIA
ELEMENTS
ENZYMES
HYDROXY COMPOUNDS
MICROORGANISMS
NONMETALS
ORGANIC COMPOUNDS
560300* - Chemicals Metabolism & Toxicology