2.7. The Verification Experiments
The verification experiments under the optimum supplement dose obtained from the analysis results
of orthogonal experiment (Section 2.6), were performed in the 500-mL air-locked flask and a 2-L
fermenter (Biostat®B, B. Braun Biotech, Melsungen, Germany). The final working volume of the 2-L
fermenter was 1.5 L, and the EP medium was sterilized at 110 °C for 40 min. The fermentation
conditions in the fermenter were the same as those previously described for the flask.
2.8. Analytical Methods
The major trace elements in raw sweet sorghum juice and yeast extract were analysed by Central
Laboratory (Thailand) Co., Ltd. (Khon Kaen, Thailand). The cell numbers in the fermentation broth
were determined by direct counting method using haemacytometer with methylene blue staining