Introduction of synthetic pathways into mannheimia succiniciproducens for the succinic acid production

Abstract

Succinic acid is a four-carbon dicarboxylic acid synthesized as an intermediate of the tricarboxylic acid cycle and also as one of the mixed-acid fermentation products, which can be used in many applications. From last decades, several researches have been carried out to develop a microbial succinic acid production process. However, high substrate cost, low productivity, and expensive purification cost have been an obstacle for industrial application of microbial succinic acid fermentation process. Mannheimia succiniciproducens which is a capnophilic Gram-negative bacterium isolated from bovine rumen was able to produce a large amount of succinic acid as a major fermentation product. Based on whole genome sequence of M. succiniciproducens, Chemically Defined Medium for M. succiniciproducens was developed to enhance the performance of succinic acid production. However, high substrate cost for medium was still remained as problem, although the productivity was improved. Hence, here we describe a method for developing succinic acid production system using reduced-chemically defined medium. Introduction of amino acid and vitamins biosynthetic pathways effectively restored the cell growth as well as the succinic acid production, although Methionine, pyridoxine, or nicotinic acid which are the essential compounds for M. succiniciproducens were removed from the chemically defined medium. By replacing the external nutrients supplement to the self synthesizing system, the medium cost as well as fermentation process cost was able to be reduced. Consequently, we could develop a cost-competitive succinic acid producer by metabolic engineering of M. succiniciproducens MBEL55E and PALK recombinants based on its genome data and reduced-chemically defined medium utilized by it. Furthermore, the method and strategies developed in this study can be applied to further cost-competitive strain development for industrial commercialization.