Methods for increasing the production of ethanol from microbial fermentation
First Claim
1. A continuous method for producing ethanol comprising:
- culturing in a fermentation bioreactor a strain of Clostridium ljungdahlii bacteria in a continuously fed liquid nutrient medium to provide a fermentation broth;
supplying to said fermentation bioreactor a gaseous substrate comprising carbon monoxide; and
maintaining a specific rate of CO uptake in said fermentation bioreactor at an amount of 0.3 to 2 mmol CO/gram dry cells weight of bacteria per minute in the fermentation broth after the bacteria achieve a stable cell concentration in the fermentation bioreactor;
wherein the bacteria produce both ethanol and acetate in a ratio of ethanol to acetate ranging from 1;
1 to 20;
1; and
wherein the bacteria produces both ethanol and butanol in a ratio of ethanol to butanol of 34.3 to 38.7.
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Abstract
A stable continuous method for producing ethanol from the anaerobic bacterial fermentation of a gaseous substrate containing at least one reducing gas involves culturing in a fermentation bioreactor anaerobic, acetogenic bacteria in a liquid nutrient medium; supplying the gaseous substrate to the bioreactor; and manipulating the bacteria in the bioreactor by reducing the redox potential, or increasing the NAD(P)H TO NAD(P) ratio, in the fermentation broth after the bacteria achieves a steady state and stable cell concentration in the bioreactor. The free acetic acid concentration in the bioreactor is maintained at less than 5 g/L free acid. This method allows ethanol to be produced in the fermentation broth in the bioreactor at a productivity of greater than 10 g/L per day. Both ethanol and acetate are produced in a ratio of ethanol to acetate ranging from 1:1 to 20:1.
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Citations
12 Claims
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1. A continuous method for producing ethanol comprising:
culturing in a fermentation bioreactor a strain of Clostridium ljungdahlii bacteria in a continuously fed liquid nutrient medium to provide a fermentation broth;
supplying to said fermentation bioreactor a gaseous substrate comprising carbon monoxide; and
maintaining a specific rate of CO uptake in said fermentation bioreactor at an amount of 0.3 to 2 mmol CO/gram dry cells weight of bacteria per minute in the fermentation broth after the bacteria achieve a stable cell concentration in the fermentation bioreactor;
wherein the bacteria produce both ethanol and acetate in a ratio of ethanol to acetate ranging from 1;
1 to 20;
1; and
wherein the bacteria produces both ethanol and butanol in a ratio of ethanol to butanol of 34.3 to 38.7.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
Specification