2.7. Fermentation
K2HPO4, (NH4)2SO4, and MgSO4 were supplemented into the sterilized stalk juice before the fermentations were carried out in the shaking flasks according to Table 2. For all the experiments in the shaking flasks, the fermentation conditions were maintained as follows: temperature 32 °C, pH 4.0, particles stuffing rate 30–33%, and agitation rate 150 rpm. An optimal inorganic salts supplement dose could be determined by the fermentation experiments in the shaking flasks. In order to verify the reliability of the results from the shaking flasks, some experiments in the fluidized bed bioreactor were conducted with the optimum inorganic salts supplement dose and blank. For all runs, temperature and pH were maintained within 32±1 °C, and 4.0±0.5, respectively. The immobilized yeast particles stuffing rate was controlled within 30–33%. The gas flux ratio between inlet and outlet was 1:6–10.