|Identification of mannose uptake and catabolism genes in Corynebacterium glutamicum and genetic engineering for simultaneous utilization of mannose and glucose.
Appl. Microbiol. Biotechnol. 89: 1905-1916. 2011.
M. Sasaki, H. Teramoto, M. Inui and H. Yukawa.
Here, focus is on Corynebacterium glutamicum mannose metabolic genes with the aim to improve this industrially important microorganism's ability to ferment mannose present in mixed sugar substrates. cgR_0857 encodes C. glutamicum's protein with 36% amino acid sequence identity to mannose 6-phosphate
isomerase encoded by manA of Escherichia coli. Its deletion mutant did not grow on mannose and exhibited noticeably reduced growth on glucose as sole carbon sources. In effect, C. glutamicum manA is not only essential for growth on mannose but also important in glucose
metabolism. A double deletion mutant of genes encoding glucose and fructose
permeases (ptsG and ptsF, respectively) of the phosphoenolpyruvate-dependent phosphotransferase
system (PTS) was not able to grow on mannose unlike the respective single
deletion mutants with mannose utilization ability. A mutant deficient in
ptsH, a general PTS gene, did not utilize mannose. These indicate that the
glucose-PTS and fructose-PTS are responsible for mannose uptake in C. glutamicum. When cultured with a glucose and mannose mixture, mannose utilization of manA-overexpressing strain CRM1 was significantly higher than that of its wild-type
counterpart, but with a strong preference for glucose. ptsF-overexpressing strain CRM2 co-utilized mannose and glucose, but at a total
sugar consumption rate much lower than that of the wild-type strain and
CRM1. Strain CRM3 overexpressing both manA and ptsF efficiently co-utilized mannose and glucose. Under oxygen-deprived conditions, high volumetric productivity of organic acids concomitant with the simultaneous consumption of the mixed sugars was achieved by the densely packed growth-arrested CRM3 cells.