Mutant E. coli strain with increased succinic acid production

Abstract

A method for isolating succinic acid producing bacteria is provided comprising increasing the biomass of an organism which lacks the ability to catabolize pyruvate, and then subjecting the biomass to glucose-rich medium in an anaerobic environment to enable pyruvate-catabolizing mutants to grow.The invention also provides for a mutant that produces high amounts of succinic acid, which has been derived from a parent which lacked the genes for pyruvate formate lyase and lactate dehydrogenase, and which belongs to the E.coli Group of Bacteria.

The embodiment of the invention in which an exclusive property or privilege is claimed is defined as follows:  
     
       1. A method for isolating succinic acid producing bacteria comprising: 
       a.) isolating a facultative organism lacking the capacity to catabolize pyruvate under fermentative conditions;  
       b.) increasing the biomass of the organism in an aerobic process;  
       c.) subjecting the biomass to glucose-rich medium in an anaerobic environment to enable pyruvate-catabolizing mutants to grow; and  
       d.) isolating a mutant characterized in that it produces a mixture of succinic acid, acetic acid and ethanol as fermentation products, which has been derived from a parent which lacked the genes for pyruvate formate lyase and lactate dehydrogenase which belongs to the E. coli Group of Bacteria.  
     
     
       2. The method as recited in claim  1  wherein the facultative organism lacks pyruvate formate lyase and lactate dehydrogenase activity. 
     
     
       3. The method as recited in claim  1  wherein the facultative organism lacking the capacity to catabolize pyruvate is NZN 111. 
     
     
       4. The method as recited in claim  1  wherein the organism is cultured aerobically on Luria broth. 
     
     
       5. The method as recited in claim  1  wherein the biomass is increased to between approximately 10 9  to 10 10  cells per milliliter. 
     
     
       6. The method as recited in claim  1  wherein the glucose-rich medium contains between approximately 1 g/l and 30 g/l of glucose. 
     
     
       7. A mutant characterized in that it produces a mixture of succinic acid, acetic acid and ethanol as fermentation products, which has been derived from a parent which lacked the genes for pyruvate formate lyase and lactate dehydrogenase which belongs to the E. coli Group of Bacteria. 
     
     
       8. A mutant as described in claim  7  wherein the parent is NZN 111. 
     
     
       9. AFP 111, as claimed in claim  7 . 
     
     
       10. A mutant as described in claim  7  wherein succinic acid is the major fermentation product.