Bacteria glutamicum Escherichia coli

L-Threonine is produced by some auxotrophic mutants and/or threonine-analog resistant mutants and those bred by gene engineering techniques. The bacteria are Escherichia coli, Corynebacterium glutamicum, Brevibacterium lactofermentum, B.flavum, Serratia marcescens, and Proteus retgerii. 

Efforts to develop organisms that overproduce L-phenylalanine have been vigorously pursued by the Nutrasweet Company, Ajinomoto, Kyowa Hakko Kogyo, and others. The focus has centered on bacterial strains that have previously demonstrated the ability to overproduce other amino acids. Such organisms include principally the coryneform bacteria, Brevibacterium flavum [1,2] and Corynebac-terium glutamicum [3,4] used in L-glutamic acid production. In addition, Escherichia coli has been extensively studied for L-phenylalanine manufacture due to... 

Vrljic et al. cloned a new gene lysE from Corynebacterium glutamicum and showed that it encodes the translocator which specifically exports L-lysin out of the cell [10]. Recently they analyzed the membrane topology of the gene product and showed that it is a member of a family of proteins found in some bacteria -Escherichia coli, Bacillus subtilis, Mycobacterium tuberculosis, and Helicobacter pylori. The authors suggested that LtsE superfamily members will prove to catalyze the export of a variety of biologically important solutes including amino acids [11-13]. 

L-Threonine is produced by some auxotrophic mutants or threonine-analogue-resistant mutants, and those are created by genetic engineering techniques. The bacteria used are Escherichia coli, Corynebacterium glutamicum, Brevibacterium lactofermentum, B. flavum, Serratia marcescens, and Proteus rettgeri (Nakamori 1986). L-Threonine production by fermentation was started in the 1970s. The auxotrophic mutant and analogue-resistant mutant strains obtained for this purpose were cultured in the presence of amino acids required by the mutant. 

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