Fig. 4

Effect of the pretreatment and genetic modification on the growth of the engineered strains. A Spot assays of the strains P8S09, P8S10, P8SB2 and P8SB4 on the plates using untreated, acid- or activated carbon (AC)-pretreated molasses. B Transcriptional level of chaperonins-related genes in strain P8S10 compared to that of strain P8S09 using molasses (with 16S rDNA as the internal reference). C Butanol tolerance test of the strains P8SB2 and P8SB4 with 0, 3, 6 and 9 g/L butanol, respectively