3.4. Bacterial fermentation
Kachrimanidou et al. (2014) employed crude glycerol and whole
SFM hydrolysates for the production of up to 27 g L−1 of PHB.
In this study, the remaining streams resulting after the extraction
of antioxidant-rich fractions and protein isolate have been
used for the production of nutrient-rich media for PHB production.
In the bioeconomy era, it is vital to exploit all nutrients
contained in renewable resources including carbon sources, nitrogen
sources, phosphorus as well as various minerals and growth
factors. SFM contains all necessary nutrients required to produce
PHB via fermentation. To prove this concept, three fed-batch bioreactor
fermentations were conducted using crude glycerol and three
different hydrolysates as nutrient supplements with the strain C.
necator DSM 7237. The production of hydrolysates I (Fig. 6) and II
(Fig. 7) was described in the previous section. Hydrolysate II was
diluted with tap water in order to adjust the initial FAN concentration.
Hydrolysate III was produced as in the case of hydrolysate II
but dilution of this stream was carried out with water employed
for washing of remaining hydrolysis solids. The solids that remain
after the recovery of hydrolysate II via vacuum filtration contain
significant quantities of nutrients, and washing these solids with
water leads to the production of a medium rich in nutrients.
In the fermentation that was carried out with hydrolysate I, the initial FAN concentration was 413mgL−1, and the initial