Fig. 5

Semi-continuous ABE fermentation of C. beijerinckii with WRD and ER as substrate. The strain was incubated in 750 ml GM with 16.6% WRD and 8.3% ER as carbon source. There was no medium replacement for the first 16 h of fermentation and the stirring was set to 50 rpm. Afterwards, stirring was set to 200 rpm and fermentation broth in the fermenter was continuously replaced with sterile new GM medium without carbon source at a D of 0.058 h.⁻¹. The fermentation was maintained for 120 h. Samples of the fermentation broth were taken every 24 h. Error bars represent standard deviation (N = 2)