Klg. Ho et al., OPTIMIZATION OF L-(-LACTIC ACID PRODUCTION BY RING AND DISC PLASTIC COMPOSITE SUPPORTS THROUGH REPEATED-BATCH BIOFILM FERMENTATION()), Applied and environmental microbiology, 63(7), 1997, pp. 2533-2542
Four customized bioreactors, three with plastic composite supports (PC
S) and one,vith suspended cells (control), were operated as repeated-b
atch fermenters for 66 days at pH 5 and 37 degrees C, The working volu
me of each customized reactor was 600 ml, and each reactor's medium wa
s changed every 2 to 5 days for 17 batches, The performance of PCS bio
reactors in long-term biofilm repeated-batch fermentation was compared
with that of suspended-cell bioreactors in this research, PCS could s
timulate biofilm formation, supply nutrients to attached and free susp
ended cells, and reduce medium channelling for lactic acid production,
Compared with conventional repeated-hatch fermentation, PCS bioreacto
rs shortened the lag time by threefold (control, 11 h; PCS, 3.5 h) and
sixfold (control, 9 h; PCS, 1.5 h) at yeast extract concentrations of
0.4 and 0.8% (wt/vol), respectively, They also increased the lactic a
cid productivity of Lactobacillus casei subsp. rhamnosus (ATCC 11443)
by 40 to 70% and shortened the total fermentation time by 28 to 61% at
all yeast extract concentrations, The fastest productivity of the PCS
bioreactors (4.26 g/liter/h) was at a starting glucose concentration
of 10% (wt/vol), whereas that of the control (2.78 g/liter/h) was at 8
% (wt/vol), PCS biofilm lactic acid fermentation can drastically impro
ve the fermentation rate with reduced complex-nutrient addition.