Alcohol production process

1. A method for optimising ethanol production in a continuous fermentation process, the method comprising;

a) providing a gaseous substrate comprising CO to a bioreactor comprising a culture of at least one carboxydotrophic acetogenic microorganismin a fermentation broth;

b) fermenting the substrate to produce ethanol and acetate;

c) adjusting the substrate supply to the fermentation broth such that the microorganism produces hydrogen;

d) determining an optimum hydrogen production;

e) monitoring the hydrogen production; and

f) adjusting the substrate supply in response to a change in the hydrogen production such that ethanol production is optimized.

2. The method of claim 1 where the hydrogen produced is at least 0.5 mol % of the CO substrate consumed.

3. The method of claim 1 where the hydrogen produced is maintained in the range of about 0.5 mol % to about 2.0 mol % of the CO substrate consumed.

4. The method of claim 1 where the hydrogen produced is at least 1.0 mol % of the CO substrate consumed.

5. The method of claim 1 wherein the substrate comprises at least 15% to 95% CO by volume.

6. The method of claim 1 wherein the carboxydotrophic acetogenic micro-organism is selected from the group consisting of Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribacterium and Peptostreptococcus.

7. The method of claim 6 wherein the carboxydotrophic acetogenic micro-organism is selected from the group consisting of Clostridium autoethanogenum, Clostridium ljungdahlii, Clostridium ragsdalei and Clostridium carboxydivorans.