0.30 g/g sugars and the productivity was 0.12 g/L/h. When the
solid loading increased to 6.3%, about 12.7 g/L of glucose and
5.3 g/L of xylose were released in the solution at 24 h. Glucose
continued to increase and reached 15.4 g/L at 48 h. After that,
glucose decreased quickly to 1.5 g/L from 48 to 120 h. Xylose
decreased gradually to 2.3 g/L at 120 h. Butyric acid reached
3.7 g/L at 24 h, then decreased slowly to 1.8 at 120 h. Acetic acid
reached 3.7 g/L at 24 h and was not changed until 120 h. At the
end of fermentation, the total solvent concentration reached
16.3 g/L, the solvent yield was 0.27 g/g sugars and the solvent
productivity was 0.14 g/L/h.
When the solid loading increased to 7.4, about 14.5 g/L of glucose
and 6.7 g/L of xylose were released in the solution at 24 h.
Glucose continued to increase and reached 18.0 g/L at 48 h. After
that, glucose decreased quickly from 17.0 to 1.5 g/L during the period
of 72–120 h. Xylose decreased slowly from 6.7 to 4.3 g/L at
120 h. Butyric acid reached 4.1 g/L at 24 h, then decreased to 1.8
at 120 h. Acetic acid reached 4.1 g/L at 24 h and was not changed
until 120 h. At the end of fermentation, the total solvent concentration
reached 18.0 g/L, the solvent yield was 0.275 g/g sugars and
the solvent productivity was 0.15 g/L/h. Comparing the solvent
yield at different solid loading, higher solid loading resulted in
lower solvent yield. It was most likely due to the decreasing
hydrolysis yield at higher solid loading, which has been documented
as the ‘‘solids effect” (