Acetate → Sorbitol

Participants

Reaction Steps

In a sterilized 1-liter fermentor (BIOSTAT® B-DCU system, Sartorius BBI System Inc., Bethlehem, Pa., USA), 80 ml of ZW658 strain seed culture at OD600 of approximately 5 was inoculated into 720 ml of aqueous solution containing sugars and medium. The final mixed broth contained 97.2 g/L glucose, 81.0 g/L xylose, 5.7 g/L acetate (in the form of potassium acetate), 5 g/L yeast extract (YE), 2 g/L KH2PO4, 2 g/L (NH4)2SO4 and 1 g/L MgSO4.7H2O. pH was adjusted to 5.5 with 4 N KOH solution. Mixing speed was set at 150 rpm. Fermentation was conducted at 33° C. and pH 5.5. Samples were taken periodically. Samples were filtered through 0.22 micron filters, and the filtrates were analyzed by HPLC as described in General Methods for compounds including glucose, xylose, xylitol, ethanol, and acetic acid. Samples were also diluted with medium (as described in General Methods) and the OD600 was measured to monitor cell growth. FIG. 14 shows the amounts of glucose, xylose, ethanol and acetic acid present, as well as the OD600 at time points between 0 and 140 hr. After 63 hours, the glucose and xylose concentrations were 0 and 50 g/L, respectively, and the ethanol concentration reached 61.8 g/L. Cells grew to an OD600 of 3.3. After 135 hours, the xylose concentration was reduced to 38 g/L, and the ethanol concentration reached 64.4 g/L. The by-product xylitol concentration was 1.3 g/L at 63 hr, and increased to 4.4 g/L after 135 hr. When the 4.4 g/L of xylitol produced at stationary phase of the fermentation culture with no sorbitol was compared to the 3.55 g/L of xyliitol produced at stationary phase of the fermentation culture with sorbitol (Example 6), the results showed that adding sorbitol reduced the amount of xylitol produced in the presence of acetate.

Provenance & Evidence