Fig. 5 presents the profile change of protease activity during
SSF of A. oryzae cultivated on LF as the sole solid substrate. The
protease activity increased up to 57 h when the highest activity is
obtained (165Ug−1) followed by a decreasing trend. The highest
protease activity (Fig. 5) achieved in this study using LF as substrate
was lower than the respective highest activity (400Ug−1 at
48 h) produced when SFM was used as substrate (Kachrimanidou
et al., 2013). Nevertheless, the protease activity produced was sufficient
in order to achieve efficient hydrolysis of remaining fractions
regarding FAN production (Figs. 6 and 7). Protein and phytic acid
hydrolysis resulted in the production of FAN and IP. Besides hydrolysis
of residual stream components, nutrients are also produced
due to fungal autolysis initiated by oxygen depletion.
Fig. 6 presents the profile change of FAN and IP when two different
initial concentrations of LF (50 and 100 g L−1) were used.
These concentrations include both the LF used in SSF and the
unprocessed LF added prior to initiation of hydrolysis. The initial
concentrations of FAN and IP at the beginning of hydrolysis
were subtracted from each experimental result. Both FAN and IP
production reached a plateau after approximately 40 h. The maximum
FAN production (505mgL−1) was achieved when an initial
concentration of 100 g L−1 of LF was employed. IP production follows
a similar trend with amaximum concentration of 93.7mgL−1
at 46 h. The obtained concentrations of FAN and IP from LF
hydrolysis are significantly lower compared to those reported by
Kachrimanidou et al. (2013) that conducted similar experiments
with SFM (1.5 g L−1 and 246mgL−1, respectively). The hydrolysate
produced by using 100 g L−1 of initial LF concentration was used as
hydrolysate I in subsequent fermentations.