In general, significant changes in organic acids concentrationsmainly
occurred during the stationary phase (days 2 to 5), as shown in Fig. 3.
Citrate concentration decreased at the start of stationary phase likely
due to itsmetabolismvia the TCA cycle and/or glyoxylate pathway (Figs.
2 and 3A). The channelling of citrate for gluconeogensis via the
glyoxylate pathway coincided with the significant increase in glucose
on day 3.While some studies have demonstrated the use of Y. lipolytica
for the production of citrate (Levinson et al., 2007; Papanikolaou et al.,
2008; Saygün et al., 2014), this phenomenon was not observed in the
present work. In those studies, citrate production by Y. lipolytica was
induced by excess carbon and limited nitrogen in the media, while the
okara substrate in this study contained low amounts of free sugars
(limited carbon) and considerable amounts of free amino acids (excess
nitrogen).