Fig. 2

Improved production of TB. a The biomass of S. ahygroscopicus S91-ΔNB and the multicopy ttmD strains. The S91-ΔNB::TD, S91-ΔNB::2TD, and S91-ΔNB::3TD strains have two copies, three copies, and four copies of ttmD, respectively. b Transcriptional analysis of the ttmD in S91-ΔNB and the multicopy ttmD strains using qRT-PCR. The ttmD was under the control of the hrdB promoter. The relative values for the ttmD in the S91-ΔNB strain was assigned as 1, with hrdB as the internal control. c The content analysis of TA and TB in S91-ΔNB and the multicopy ttmD strains at 24 h, 48 h, 72 h, and 96 h. d The HPLC analysis of fermentation products in S91-ΔNB and the multicopy ttmD strains. Error bars depict standard deviation of three replicates. ***P<0.001, **P<0.01, *P<0.05, and “ns”means not significant