FIG 6.

Cell growth and ethanol fermentation of Z. mobilis recombinant strains in various culture systems containing different levels of p-benzoquinone (BQ). (a) In RM synthetic medium containing 200 mg/liter of BQ. (b) In low-sugar corn stover hydrolysate amended with 200 mg/liter of BQ. (c) In high-sugar corn stover hydrolysate containing 110 mg/liter of BQ without BQ addition. The recombinant strain harboring the empty pHW20a served as the control strain. The cell growth and ethanol production were measured at 16 h for RM medium fermentation, 24 h for low-sugar hydrolysate fermentation, and 72 h for high-sugar hydrolysate fermentation. Conditions were as follows: 10% (vol/vol) inoculum size and 30°C in static-state culture. Error bars represent two standard deviations.