Figure Captions
Figure 1 . Experimental setup for the continuous fermentation
with clostridial cells immobilized in a fibrous bed bioreactor (FBB).
Inset diagram shows the construction of the spirally wound fibrous
matrices with stainless steel wire mesh as the mechanical support with
gaps between adjacent layers as flow channels for liquid, gas, and
solids (cells) to move freely. The highly porous fibrous matrix has a
large surface area and void volume (>90% reactor volume)
to allow high densities of viable cells (up to 100 g/L cell dry weight)
to be immobilized by attachment to fiber surfaces and entrapment within
the matrix.
Figure 2 . Effect of butyric acid on cell growth. Cells ofC. acetobutylicum ATCC 55025 were cultured in P2 medium
containing 20 g/L glucose and various amounts of butyric acid (0, 2, 5,
or 10 g/L) in serum bottles at 37 oC.
Figure 3 . Kinetics of batch fermentation with free cells
cultured in medium containing ~50 g/L glucose and 4 g/L
butyric acid as carbon sources in a stirred-tank bioreactor at 35oC and pH controlled at ~5.0.
Figure 4 . Kinetics of continuous fermentation with 50 g/L
glucose and 4 g/L butyric acid at the dilution rate of 0.06
h-1. (a) Time course data of cell density (OD),
glucose, solvents (acetone, butanol, and ethanol), and acids (acetic
acid and butyric acid) in the reactor outlet stream; (b) Butanol and ABE
yields and butanol productivity.
Figure 5 . Kinetics of continuous fermentation with 60 g/L
glucose and 6.8 g/L butyric acid at the dilution rate of 0.12
h-1. (a) Time course data of cell density (OD),
glucose, solvents (acetone, butanol, and ethanol), and acids (acetic
acid and butyric acid) in the reactor outlet stream; (b) Butanol and ABE
yields and butanol productivity.
Figure 6 . Kinetics of continuous fermentation with 60 g/L
glucose and 5.0 g/L butyric acid at the dilution rate of 1.88
h-1. (a) Time course data of cell density (OD),
glucose, solvents (acetone, butanol, and ethanol), and acids (acetic
acid and butyric acid) in the reactor outlet stream; (b) Butanol and ABE
yields and butanol productivity.
Figure 7. Scanning electron micrographs of cells immobilized in
the fibrous matrix in the fibrous bed bioreactor. Cells adsorbed on the
fiber surface formed a thick layer of biofilm. Most of cells had an
elongated rod shape between 3 to 5 µm.
Table 1. Comparison of
fermentation kinetics of C. acetobutylicum ATCC55025 in batch and
continuous fermentations at different dilution rates.