title: Efficient 40 degrees C fermentation of L-lysine by a new Corynebacterium glutamicum mutant developed by genome breeding.
abstract: We have recently developed a new L-lysine-producing mutant of Corynebacterium glutamicum by "genome breeding" consisting of characterization and reconstitution of a mutation set essential for high-level production. The strain AHP-3 was examined for L-lysine fermentation on glucose at temperatures above 35 degrees C, at which no examples of efficient L-lysine production have been reported for this organism. We found that the strain had inherited the thermotolerance that the original coryneform bacteria was endowed with, and thereby grew and produced L-lysine efficiently up to 41 degrees C. A final titer of 85 g/l after only 28 h was achieved at temperatures around 40 degrees C, indicating the superior performance of the strain developed by genome breeding. When compared with the traditional 30 degrees C fermentation, the 40 degrees C fermentation allowed an increase in yield of about 20% with a concomitant decrease in final growth level, suggesting a significant transition of carbon flux distribution in glucose metabolism. DNA array analysis of metabolic changes between the 30 degrees C and 40 degrees C fermentations identified several differentially expressed genes in central carbon metabolism although we could not find stringent control-like global induction of amino-acid-biosynthetic genes in the 40 degrees C fermentation. Among these changes, two candidates were picked out as the potential causes of the increased production at 40 degrees C; decreased expression of the citrate synthase gene gltA and increased expression of malE, the product of which involves regeneration of pyruvate and NADPH.
authors.affiliation: Tokyo Research Laboratories, Kyowa Hakko Kogyo, Asahi-machi, Machida, 194-8533 Tokyo, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Ohnishi
authors.forename: M
authors.initials: M
authors.lastname: Hayashi
authors.forename: S
authors.initials: S
authors.lastname: Mitsuhashi
authors.forename: M
authors.initials: M
authors.lastname: Ikeda
mesh_terms: D003352:Corynebacterium / Q000235:genetics* / Q000378:metabolism; D003470:Culture Media; D005285:Fermentation; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D006358:Hot Temperature; D007218:Industrial Microbiology / Q000379:methods; D008239:Lysine / Q000096:biosynthesis / Q000378:metabolism*; D008957:Models, Genetic; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods
chemical_list: D003470:Culture Media; D008239:Lysine