Pilot-Scale Polyhydroxyalkanoate Production from Organic Waste: Process Characteristics at High pH and High Ammonium Concentration

Abstract

A polyhydroxyalkanoate (PHA) accumulating microbial enrichment was established on a volatile fatty acids (VFA) containing leachate derived from the organic fraction of municipal solid waste (OFMSW). The enrichment was based on a 12 h feast-famine batch cycle and an exchange ratio of 50% in which VFA were completely consumed in less than 50 minutes during stable periods of operation. No pH control was applied 2 in the system and the pH went as high as 9 due to the presence of amongst others ammonia (500 mg•L -1 total ammonia nitrogen (TAN) on average). The degree of enrichment was evaluated with fluorescence in situ hybridization (FISH) and a yet unknown genus of large (3-5 m diameter) beta-proteobacteria appeared dominant in the culture. A method for estimating the fraction of PHA accumulating active biomass in the total VSS was established: results indicated an increase of this fraction from 25 to 56% after implementing two modifications in the operational protocol: (i) a pretreatment of the substrate removing virtually all settleable solids and (ii) a settling phase in the enrichment reactor after the feast phase, selectively removing non-settleable solids and slowly degradable substrates. The PHA accumulation potential of the culture was 77 ± 18 wt% PHA (n=3) after 3 h in batch accumulation experiments. The results suggest the potential feasibility of PHA production under conditions that were previously considered economically favourable but technically difficult.

Pilot scale production and evaluation of mechanical and thermal properties of P(3HB) from Bacillus megaterium cultivated on desugarized sugar beet molasses

“…22 An alternative to the cultivation of pure cultures are non-sterile processes based on mixed cultures, which are mostly wastewater based and have meanwhile been realized at pilot scale. 19 Reported concentrations of PHA in CDM of 0.45-0.5 g/g and 0.77 g/g, respectively, 43,44 are in a similar range or even higher compared to our results. It is expected that mixed culture fermentations can provide robust continuous processes for the production of large amounts of cheap PHA that could be used for low grade products or compounded with other biodegradable polymers.…”

Circular closed-loop waste biorefineries: Organic waste as an innovative feedstock for the production of bioplastic in South Africa

“…Another pilot-scale study analysed the production of PHA from OFMSW at high pH and ammonia concentrations. 31 These authors found that the highest PHA accumulation of 77 wt% occurred as pH increased towards 9 and the ammonia concentration was 500 mg/L. Several biofuel processes, such as biomethane, biohydrogen and bioethanol, result in volatile fatty acid (VFA) production as a byproduct.…”

From Organic Wastes and Hydrocarbons Pollutants to Polyhydroxyalkanoates: Bioconversion by Terrestrial and Marine Bacteria

“…The study of Mulders et al [79] is of particular interest, since here, a polymer with 50% w/w 3HV was produced by the selected MMC; in this case, uncultured Rhodocyclaceae was grown on fermented organic waste at a high OLR (up to 8.0 gCOD/L d). Additionally, Pereira et al [73] showed the presence of Rhodobacter and Rhizobium (16.3%) at a high OLR, producing PHA at a high 3HV level (38% w/w).…”