Continuous process for ethanol production by bacterial fermentation using pH control
First Claim
1. A continuous process for the production of ethanol, which comprisesfeeding an aqueous substrate solution substantially continuously to a reactor containing a fermentation medium and a submerged culture of an organism of the genus Zymomonas;
- cultivating said organism to produce ethanol under substantially steady state anaerobic conditions in an aqueous nutrient medium containing assimilable carbon, nitrogen and phosphorus;
controlling pH in the fermentation medium between a pH of about 3.8 and a pH less than 4.5 so that ethanol production is substantially uncoupled from cell growth and wherein the biomass expresses values for both the specific rate of substrate uptake (qs) and the specific rate of ethanol formation (qp) which are greater than the values would be for a similar process conducted at a higher pH; and
removing an effluent containing ethanol from the reactor.
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Abstract
A continuous process for the production of ethanol by fermentation of an organism of the genus Zymomonas is provided. The method is carried out by cultivating the organism under substantially steady state, anaerobic conditions and under conditions in which ethanol production is substantially uncoupled from cell growth. By controlling pH in the fermentation medium between a pH of about 3.8 and a pH less than 4.5, it is possible to optimize kinetic parameters, such as qs (g substrate/g biomass-hr-1) and qp (g ethanol/g biomass-hr-1) without adversely affecting ethanol concentration in the fermentation medium.
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Citations
11 Claims
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1. A continuous process for the production of ethanol, which comprises
feeding an aqueous substrate solution substantially continuously to a reactor containing a fermentation medium and a submerged culture of an organism of the genus Zymomonas; -
cultivating said organism to produce ethanol under substantially steady state anaerobic conditions in an aqueous nutrient medium containing assimilable carbon, nitrogen and phosphorus; controlling pH in the fermentation medium between a pH of about 3.8 and a pH less than 4.5 so that ethanol production is substantially uncoupled from cell growth and wherein the biomass expresses values for both the specific rate of substrate uptake (qs) and the specific rate of ethanol formation (qp) which are greater than the values would be for a similar process conducted at a higher pH; and removing an effluent containing ethanol from the reactor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification