Characterization of Polyhydroxyalkanoates Produced at Pilot Scale From Different Organic Wastes

Abstract

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.

Ethylic Esters as Green Solvents for the Extraction of Intracellular Polyhydroxyalkanoates Produced by Mixed Microbial Culture

“…The different M v of the two R-PHA samples is likely due to the different stabilization methods [ 43 , 44 ]. In fact, it has been previously observed how the thermal treatment, used for the stabilization of Biomass1, led to a molecular weight reduction, due to partial polymer hydrolysis favored by high temperature.…”

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

“…22 Molecular weight is, however, similar to polymers obtained in pilot scale PHA production from mixed cultures on substrates like waste water or municipal waste, which is reported in the range of 430 or 208 kDA. 45 In a previous publication we could show that rupturing the cell walls with ultrasonication improved the extraction yield of P(3HB) from B. megaterium to 90% 22 ; however, due to the required quantities of energy ultrasonication is currently not an option on a larger scale. Other methods like mechanical cell rupture, enzymatic cell lysis 26 or controlled autolysis 27 in combination with solvent extraction might result in a higher product recovery.…”

“…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. 45 On the other hand, the process presented in this work is based on a defined substrate with a pure culture, which allows the implementation of a reproducible fermentation procedure. Repeated batch cultivation is easier to handle than a continuous process and less prone to failure.…”

Combined Strategies to Prompt the Biological Reduction of Chlorinated Aliphatic Hydrocarbons: New Sustainable Options for Bioremediation Application

“…Indeed, PHA-accumulating organisms can be selected from typical activated sludge from wastewater treatment plants using Aerobic Dynamic Feeding (ADF) conditions [ 42 ]. Lorini and colleagues (2021) pointed out the possibility of exploiting various organic biowaste as a raw material for the production of purified PHA with properties comparable to those of commercial plastics [ 43 ]. The investigated PHA were produced in three pilot platforms: in Treviso (Northeast of Italy) [ 41 ], Carbonera (Northeast of Italy) [ 44 ], and Lisbon.…”

“…The investigated PHA were produced in three pilot platforms: in Treviso (Northeast of Italy) [ 41 ], Carbonera (Northeast of Italy) [ 44 ], and Lisbon. Each process was based on the selection and enrichment of PHA-producing biomass from MMCs and the exploitation of different fermentable organic waste (i.e., a mixture of the organic fraction of municipal solid waste and sewage sludge; cellulosic primary sludge; fruit waste, respectively) [ 43 ]. Recently, our research group examined the fermentability of these innovative PHA materials in comparison with commercial ones.…”