2.4.2. Production of LA from corn stover in a 5-L bioreactor
Five percent NaOH-pretreated and washed corn stover, 10 g/L
yeast extract, and cellulase at a concentration of 30 FPU/g stover
were inoculated with 300 mL seed culture to establish SSF process
in a 3-L volume. Fermentation was carried out at 50 C for 60 h,
with agitation at 100 rpm. The pH was maintained at 6.0 by using
an automatic feed of 10 M NaOH solution. Fed-batch fermentations
were carried out with 8% pretreated corn stover with washing,
150 mL seed culture, and a cellulase concentration of 30 FPU/g
stover in a total volume of 1.5 L. During fermentation, washed
(5.2%) or unwashed (6.4%) corn stover were continuously fed,
and the total fermentation volume reached approximately 3 L.
Enzyme feeding for all fermentations is illustrated in Fig. 5, and
the final enzyme concentration was 30 FPU/g stover. Samples were
collected every 6 or 12 h, and LA, acetic acid, glucose, and xylose
concentrations were determined by HPLC. The fed corn stover
was not sterilized, and fermentation was carried out under non-sterile
conditions.