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.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThis invention relates to a method to produce succinic acid, malic acid or fumaric acid, and more particularly this invention relates to a bacteria that produces high quantities of succinic acid, malic acid and fumaric acid.2. Background of the InventionCarboxylic acids hold promise as potential precursors for numerous chemicals. For example, succinic acid can serve as a feedstock for such plastic precursors as 1,4-butanediol (BDO), tetrahydrofuran, and gamma-butyrolactone. New products derived from succinic acid are under constant development, with the most notable of these being polyester which is made by linking succinic acid and BDO. Generally, esters of succinic acids have the potential of being new, "green" solvents that can supplant more harmful solvents and serve as precursors for millions of pounds of chemicals annually at a total market value of over $1 billion. Along with succinic acid, other 4-carbon dicarboxylic acids,...

AI Technical Summary

Benefits of technology

Yet another object of the present invention is to provide a strain of a facultative organism which produces concentrations of malic acid in the range of 100 grams per liter. A feature of the invention is the combination of a bacterium, which does not metabolize pyruvate to malic acid, with a malic enzyme gene. An advantage of the invention is the exclusive production of malic acid, or the production of malic acid and succinic acid.

is the exclusive production of malic acid, or the production of malic acid and succinic acid.

Still another object of the present invention is to provide a strain of a facultative organism which produces succinic acid in a ratio of approximately 2:1 succinic to carbohydrate food source. A feature of the invention is the emergence of the strain after selective culturing techniques. An advantage of the invention is the economical production of succinic acid-producing mutants without the need for time consuming genetic manipulations of parent strains.

Briefly, a method for isolating succinic acid producing bacteria is provided comprising isolating a facultative organism lacking the capacity to catabolize pyruvate; increasing the biomass of the organism in an aerobic process; subjecting the biomass to glucose-rich medium in an anaerobic environment to enable pyruvate-catabolizing mutants to grow; and isolating the mutants.

The invention also provides for a mutant characterized in that it produces a mixture of succinic acid, acetic acid and ethanol as fermentation products, which as 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. On Aug. 20, 1997, this E. coli mutant was placed with the American Type Culture Collection as deposit #202021 and is designated herein as AFP 111. The ATCC is located at 12301 Parklawn Drive, Rockville, Md. 20852.

Problems solved by technology

Succinate is an intermediate for anaerobic fermentations by propionate-producing bacteria but those processes result in low yields and concentrations.

However, rumen organisms are characteristically unstable in fermentation processes.

As such, efforts to produce carboxylic acids fermentatively have resulted in relatively large amounts of growth substrates, such as glucose, not being converted to desired product.

Furthermore, the A. succiniciproducens host strain has been shown to be not highly osmotolerant in that it does not tolerate high concentrations of salts and is further inhibited by moderate concentrations of product.

Lastly, A. succiniciproducens presents handling problems in that as an obligate anaerobe, procedures using the organism must be done in the absence of oxygen.

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