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Methods for increasing the production of ethanol from microbial fermentation

  • US 20030211585A1
  • Filed: 03/11/2003
  • Published: 11/13/2003
  • Est. Priority Date: 07/25/2000
  • Status: Active Grant
First Claim
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1. A stable continuous method for producing ethanol from the anaerobic bacterial fermentation of a gaseous substrate, the method comprising:

  • culturing in a fermentation bioreactor anaerobic, acetogenic bacteria in a liquid nutrient medium and supplying to said bioreactor said gaseous substrate comprising at least one reducing gas selected from the group consisting of carbon monoxide and hydrogen; and

    manipulating said bacteria in said bioreactor by reducing the redox potential, or increasing the NAD(P)H TO NAD(P) ratio, in the fermentation broth after said bacteria achieves a stable cell concentration in said bioreactor, wherein said free acetic acid concentration in said bioreactor is less than 5 g/L free acid, said culturing and manipulating steps causing said bacteria in said bioreactor to produce ethanol in a fermentation broth at a productivity greater than 10 g/L per day and wherein both ethanol and acetate are produced in said fermentation broth in a ratio of ethanol to acetate ranging from 1;

    1 to 20;

    1.

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