The dry weight of cells at the end of fermentation was determined by centrifuging 10 mL of broth and washing the cells with double deionized H
2O. The washed cells were placed in pre-weighed aluminum dishes and dried overnight at an 85 °C incubator. The correlation between dry cell weight and OD
600 nm value was then calculated and used to estimate the dry cell weight in other time points.
Samples from the shake flasks or fermenters were taken at various time points. The samples were diluted for OD
600 nm measurement. In addition, samples were filtered through a 0.2-μm syringe filter into HPLC vials. Concentrations of glucose, xylose, 2,3-BDO, acetoin, xylitol, ethanol, HMF, furfural, lactic acid, glycerol, and acetic acid were determined from filtered sample supernatants by
Agilent 1100 series HPLC (Agilent, CA) utilizing a BioRad Aminex HPX-87H organic acids column and Cation H
+ guard cartridge (Bio-Rad, CA) operating at 65 °C. A refractive index detector was used for compound detection. Dilute sulfuric acid (0.01 N) was used as the isocratic mobile phase at a flow rate of 0.6 mL/min, following published procedures [41 (
link)]. Sugar utilization, 2,3-BDO, acetoin, and ethanol titers were calculated based on the HPLC and dry cell weight data.
Yang S., Mohagheghi A., Franden M.A., Chou Y.C., Chen X., Dowe N., Himmel M.E, & Zhang M. (2016). Metabolic engineering of Zymomonas mobilis for 2,3-butanediol production from lignocellulosic biomass sugars. Biotechnology for Biofuels, 9(1), 189.
