Hydrolysate II was produced using remaining SSF solids mixed
with the SR fraction that were suspended in the soluble fraction
(Fig. 2). Therefore, tap water and LF unprocessed solids employed
in the case of hydrolysate I production were replaced by the soluble
fraction and the SR fraction. Fig. 7 shows the profile change
of FAN and IP during hydrolysis for hydrolysate II production
using 50 and 100 g L−1 of initial solid concentrations (based on
fermented SSF solids and SR). The highest FAN and IP production
achieved were approximately 1 g L−1 and 123mgL−1 when the
initial solid concentration was 100 g L−1. The obtained values are
lower than those achieved from whole SFM (Kachrimanidou et al.,
2013) but higher than hydrolysate I (Fig. 6). In particular, FAN production
increased two fold in the case of hydrolysate II production.
This means that the exploitation of all remaining liquid and solid
streams lead to the production of hydrolysates with higher nutrient
content.
Protein hydrolysates were also produced from the PI fraction.
The solids from SSF were removed by vacuum filtration prior to
hydrolysis. Hydrolysis was carried out using 15 g L−1 PI resulting in
a FAN/TKN hydrolysis yield of around 35% (data not shown).