Glucose was almost depleted atthe end of fermentation (91.3%),
however, xylose was scarcely consumed (30.8%) after 52 h. These
results performed using 1 L of culture medium in a 2-L bioreactor
are worse thanthose attained withthe same experiment performed at a flask level (50 mL of medium in 250 mL Erlenmeyer flask), both
inoculated with the same amount of biomass, where the substrate
consumption was faster and higher. This poor performance cannot
be attributed to pH, since this value only decreased slightly during fermentation from 7.4 at time 0 to 6.24 after 52 h, due to the
increase ofthe concentration of two acids: acetic acid that rose from
0 to 0.84 g/L, but mainly to the appearance of lactic acid at 20 h of
fermentation, which was augmenting its concentration until 4.0 g/L
at the end of fermentation.