Characterization of Polyhydroxyalkanoates Produced at Pilot Scale From Different Organic Wastes
Polyhydroxyalkanoates (PHAs) production at pilot scale has been recently investigated
and carried out exploiting different process configurations and organic wastes. More in
detail, three pilot platforms, in Treviso (North-East of Italy), Carbonera (North-East of Italy)
and Lisbon, produced PHAs by open mixed microbial cultures (MMCs) and different
organic waste streams: organic fraction of municipal solid waste and sewage sludge
(OFMSW-WAS), cellulosic primary sludge (CPS), and fruit waste (FW), respectively.
In this context, two stabilization methods have been applied, and compared, for
preserving the amount of PHA inside the cells: thermal drying and wet acidification of
the biomass at the end of PHA accumulation process. Afterward, polymer has been
extracted following an optimized method based on aqueous-phase inorganic reagents.
Several PHA samples were then characterized to determine PHA purity, chemical
composition, molecular weight, and thermal properties. The polymer contained two
types of monomers, namely 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) at a
relative percentage of 92.6–79.8 and 7.4–20.2 w/w, respectively, for Treviso and Lisbon
plants. On the other hand, an opposite range was found for 3HB and 3HV monomers
of PHA from Carbonera, which is 44.0–13.0 and 56.0–87.0 w/w, respectively. PHA
extracted from wet-acidified biomass had generally higher viscosity average molecular
weights (Mv) (on average 424.8 20.6 and 224.9 21.9 KDa, respectively, for
Treviso and Lisbon) while PHA recovered from thermally stabilized dried biomass had
a three-fold lower Mv.