Ethanol production by thermophilic bacteria: biochemical basis for ethanol and hydrogen tolerance in Clostridium thermohydrosulfuricum

Journal Article · Wed Jun 01 04:00:00 EDT 1988 · J. Bacteriol.; (United States)

OSTI ID:6765379

Lovitt, R W; Shen, G J; Zeikus, J G

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), Journal Name: J. Bacteriol.; (United States) Vol. 170:6; ISSN JOBAA
• Country of Publication: United States
• Language: English

Related Subjects

560300* -- Chemicals Metabolism & Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALCOHOLS
BACTERIA
CLOSTRIDIUM
ELEMENTS
ENZYME ACTIVITY
ENZYMES
ETHANOL
GROWTH
HYDROGEN
HYDROXY COMPOUNDS
MICROORGANISMS
NONMETALS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
SENSITIVITY
THERMOPHILIC CONDITIONS
TOLERANCE
TOXICITY