Patent ID: 8586335

Claim:
A process for the production of ethanol and butanol using two separate fermentation steps comprising: a) first fermentation step comprising fermenting feedstock; wherein subjecting said feedstock to anaerobic fermentation in the presence of acetogenic bacteria, further comprising a mixture of bacterial strains, at a pH below 6.0, at a temperature in the range 20 to 70 degree C, converting said feedstock to a product predominantly comprising acetic acid and butyric acid; wherein ratio of acetic acid to butyric acid is at least 2:1; b) treating said product predominantly comprising acetic acid and butyric acid of step a) to separate a solution comprising the acetic acid and butyric acid by: (i) separating residual solids; and (ii) separating bacteria; optionally pasteurizing; optionally sterilising said solution comprising the acetic acid and butyric acid; c) second fermentation step comprising fermenting in the presence of solventogenic bacteria said solution comprising the acetic acid and butyric acid from step b) to form ethanol and butanol.