Transcriptome analysis of the pfkB1 deletion mutant cultivated with glucose or fructose

In the analysis of a carbohydrate metabolite pathway, we found that a mutant strain of Corynebacterium glutamicum deficient in pfkB1, which encodes fructose-1-phosphate kinase, showed interesting characteristics. After aerobically cultivated with fructose as a carbon source, this mutant consumed glucose and produced lactate more than 2-fold as compared with the wild-type under conditions of oxygen deprivation. This considerably higher fermentation capacity was unique for the combination of the pfkB1 deletion and fructose cultivation. On the basis of the metabolome and transcriptome analyses, we identified marked intracellular accumulation of fructose-1-phosphate and significant upregulation of several genes related to the phosphoenolpyruvate:carbohydrate phosphotransferase system, glycolysis, and organic acid synthesis in this strain. Therefore, the considerably enhanced glucose consumption and organic acid production presumably resulted from a relief of transcriptional repression driven by global regulator SugR owing to the accumulated fructose-1-phosphate. Furthermore, we demonstrated that engineered strains overexpressing the above upregulated genes showed enhanced glucose consumption and organic acid production. The ppc deletion mutant of the engineered strain consumed 1,250 mM glucose and produced 2,390 mM lactate in 48 h under oxygen deprivation, which are 2.6- and 2.7-fold higher than the corresponding parameters of the ppc-deleted wild-type. Gene expression profile of the wild type cultivated with glucose in the early log phase (at 4 h) was compared with those of the wild type cultivated with glucose in the stationary phase (at 12 h), the wild type cultivated with fructose in the early log phase (at 4 h) and stationary phase (at 12 h), and the pfkB1 deletion mutant cultivated with glucose or fructose in the early log phase (at 4 h) and in late log/stationary phases (at 12 h).