Fig. 5: Temporal control of UDP-GlcA synthesis for optimal cell growth and HA synthesis.

A The biosynthetic pathway for HA production from glucose. B, C PH, SEM, and TEM micrographs of the recombinant C. glutamicum CGHA-105 and CGHA-107 strains. D PH micrographs of recombinant E. coli and B. subtilis strains overexpressing UDP-glucose dehydrogenase (Ugd). E Volcano plot of differentially expressed proteins affected by changes in cell morphology. Orange and blue dots indicate up-regulation and down-regulation respectively. The abscissa represents the fold change in protein expression, while the ordinate represents significance changes in protein expression. F Growth and metabolism curves for C. glutamicum cells expressing Ugd and Ugd mutants (lacking catalytic activity). Ugd uses promoter Ptrc, while the mutant Ugd lacks catalytic activity, serving as a control. G Sugar composition of chain-like C. glutamicum cells determined using promoter Ptrc to overexpress Ugd, with C. glutamicum ATCC 13032 as control. H Temporal regulation of Ugd expression balances cell growth and HA synthesis. Cells in the exponential phase, and late exponential phase show Ugd expression. I Expression of the gfp gene under promoter P-N14 and its derived promoters (P-H1, P-H2, P-M1, and P-L1) in wild-type C. glutamicum. J Growth and glucose consumption of the recombinant C. glutamicum CGHA-105 and CGHA-123. Strain CGHA-123 delays the expression of Ugd by promoter PH1. K SEM and TEM micrographs of the recombinant C. glutamicum strains CGHA-123, with promoter PH-1 used for Ugd expression. Cells were cultivated for 24 h and then subjected to proteomics sequencing and cellular polysaccharide composition analysis. Statistical evaluation (p-value) was performed by a two-sided t test. The image shown is representative of n  =  3 independent replicates of experiments with similar results. All data are expressed as the mean ± S.D. from three (n = 3) biological independent replicates. Source data are provided as a Source Data file.