149
The high cost of polyhydroxyalkanoates production compared with petrochemical plastics has limited polyhydroxyalkanoates development to date with only a
handful of commercial facilities in operation (Kourmentza et al. 2017). Industrial
wastewaters are typically high strength organic laden and nutrient deficient making
them highly suitable for polyhydroxyalkanoates feedstock. Moreover, their simultaneous treatment allows cost offsetting unlike typical commercial agroindustry feedstocks which represent a significant proportion of the overall polyhydroxyalkanoates
production cost. However, due to the non-sterile nature of industrial wastewaters
and the typically open treatment systems employed at industrial facilities, microbial
mixed cultures rather than pure cultures are more suitable. Microbial mixed cultures
provide new challenges with respect to maintaining microbial communities with
high polyhydroxyalkanoates accumulation rates and yields, as well as their downstream processing for polyhydroxyalkanoates extraction due to lower biomass concentrations. Currently, microbial mixed culture systems applied to municipal and
industrial wastewaters only exist at pilot scale, and further research and development is needed to see commercialization (Kourmentza et al. 2017). Moreover, due
to the high capital investment needed, government policy and incentives may be
necessary to see the necessary paradigm shift in wastewater handling. Nevertheless,
existing techno-economic and sustainability evaluations of microbial mixed cultures for combined industrial wastewater treatment and polyhydroxyalkanoates production provide promising indicators for implementation and commercialization
(Gurieff and Lant 2007; Dacosta et al. 2015).
The major bottlenecks of the existing process include increasing biomass concentrations to simplify downstream processing, reducing energy costs associated
with aeration and polymer extraction, and developing more sustainable extraction
processes that simultaneously provide high purity and recovery. Significant developments have been made in recent years on fermentation techniques to overcome
these constraints and promote higher polyhydroxyalkanoates accumulation, yields,
and production rates and to produce selected monomers for desired properties. Such
techniques include various substrate and nutrient feeding strategies, optimized fermentation and volatile fatty acid selection, and various novel selection strategies,
including photosynthetic systems, settling selective pressures, and halophile cultures. The large variation in wastewater characteristics from industry to industry
makes this a vast area for further research and innovation, and recent microbial
mixed culture pilot-scale systems treating wastewaters (Morgan-Sagastume et al.
2015; Bengtsson et al. 2017) indicate near readiness of the technology.
Acknowledgments The authors would like to acknowledge the support of the Qatar National
Research Fund, grant NPRP11S-0110-180245.
5 Integration of Polyhydroxyalkanoates Production with Industrial Wastewater…
The high cost of polyhydroxyalkanoates production compared with petrochemical plastics has limited polyhydroxyalkanoates development to date with only a
handful of commercial facilities in operation (Kourmentza et al. 2017). Industrial
wastewaters are typically high strength organic laden and nutrient deficient making
them highly suitable for polyhydroxyalkanoates feedstock. Moreover, their simultaneous treatment allows cost offsetting unlike typical commercial agroindustry feedstocks which represent a significant proportion of the overall polyhydroxyalkanoates
production cost. However, due to the non-sterile nature of industrial wastewaters
and the typically open treatment systems employed at industrial facilities, microbial
mixed cultures rather than pure cultures are more suitable. Microbial mixed cultures
provide new challenges with respect to maintaining microbial communities with
high polyhydroxyalkanoates accumulation rates and yields, as well as their downstream processing for polyhydroxyalkanoates extraction due to lower biomass concentrations. Currently, microbial mixed culture systems applied to municipal and
industrial wastewaters only exist at pilot scale, and further research and development is needed to see commercialization (Kourmentza et al. 2017). Moreover, due
to the high capital investment needed, government policy and incentives may be
necessary to see the necessary paradigm shift in wastewater handling. Nevertheless,
existing techno-economic and sustainability evaluations of microbial mixed cultures for combined industrial wastewater treatment and polyhydroxyalkanoates production provide promising indicators for implementation and commercialization
(Gurieff and Lant 2007; Dacosta et al. 2015).
The major bottlenecks of the existing process include increasing biomass concentrations to simplify downstream processing, reducing energy costs associated
with aeration and polymer extraction, and developing more sustainable extraction
processes that simultaneously provide high purity and recovery. Significant developments have been made in recent years on fermentation techniques to overcome
these constraints and promote higher polyhydroxyalkanoates accumulation, yields,
and production rates and to produce selected monomers for desired properties. Such
techniques include various substrate and nutrient feeding strategies, optimized fermentation and volatile fatty acid selection, and various novel selection strategies,
including photosynthetic systems, settling selective pressures, and halophile cultures. The large variation in wastewater characteristics from industry to industry
makes this a vast area for further research and innovation, and recent microbial
mixed culture pilot-scale systems treating wastewaters (Morgan-Sagastume et al.
2015; Bengtsson et al. 2017) indicate near readiness of the technology.
Acknowledgments The authors would like to acknowledge the support of the Qatar National
Research Fund, grant NPRP11S-0110-180245.
5 Integration of Polyhydroxyalkanoates Production with Industrial Wastewater…