Table 2 summarizes the fermentation parameters of experiments
at various concentrations of yeast extract, such as
lactic acid produced, l(+)-lactic acid contents, lactic acid
yields, and productivities. Lactic acid yields based on total
sugar consumed were obtained to 93.7–95.5%, and the
highest yield (95.5%) was found at 10 g/l of yeast extract.
However, the maximum lactic acid productivity (5.3 g/l h)
and dry cell weight (16.1 g/l) were obtained at 20 g/l of yeast
extract. These results imply that the lactic acid fermentations
should be severely affected by yeast extract concentrations
added to the medium. Kotzamanidis et al. [19], who investigated
the effect of yeast extract on lactic acid fermentation
from beet molasses, also reported that lactic acid fermentation
was considerably stimulated by increase of yeast extract
concentrations. l(+)-Lactic acid content, however, was not