Deliverable 3.6 - C-releasing PHA

Abstract

Groundwater is an extremely important resource that may, however, contain a variety of toxic and bioaccumulative contaminants such as chlorinated solvents. Moreover, in groundwater naturally occurring microorganisms can effectively reduce chlorinated compounds, by the so-called Biological Reductive Dechlorination (BRD). The process consists of several stages to convert a toxic organic contaminant (high chlorinated ethane/ethene) to less toxic components (until ethane/ethene).

Nevertheless, the lack of electron donors is usually recognized as a limiting factor in BRD. To overcome the problem, the in-situ bioremediation of chlorinated solvents has been used based on the injection of electron donors to speed up the reductive dechlorination natural processes. In this context, the use of biopolymers known as Polyhydroxyalkanoates (PHA), which are completely biodegradable polyesters, have been advantageously used as electron donor source for sustaining in-situ BRD [1].

Even though the unique properties of PHA make them suitable for a large market, some drawbacks need to be faced, such as: the high production cost and the development of strategies able to improve PHA properties according to their final applications. The high cost of production is mainly due to the use, in industrial biotechnological processes, of pure culture fermentations which require well-defined substrate and sterile conditions. In recent years, more interest has been dedicated to PHA obtained with selected mixed microbial cultures (MMC) which can reduce the total costs by combing the waste treatment with bioplastic production [2].

Along this line, the main objective of this Task (Task 3.2.4 of WP3 in the frame of the RES URBIS project) was to investigate the fermentability of PHA obtained from waste by using MMC (from WP2) which could be an effective bio-based material for supporting Biological Reductive Dechlorination. So, in the last part of the activity the applicability of PHAs as a source of electron donor and organic carbon for the sustenance of the bacterial activity involved in BRD was tested [3].

 

[1] B. Matturro, L. Pierro, E. Frascadore, M. Petrangeli Papini and S. Rossetti, 2018, “Microbial Community Changes in a Chlorinated Solvents Polluted Aquifer Over the Field Scale Treatment with Poly-3-Hydroxybutyrate as Amendment” Front. Microbiology, 9, 1664.

[2] F. Valentino, F. Morgan-Sagastume, S. Campanari, M. Villano, A. Werker and M. Majone, 2017, “Carbon recovery from wastewater through bioconversion into biodegradable polymers”, New Biotechnology, 9, 9-23.

[3] P. Mannino, V. CeccarelliL., 2014, “Poly-hydroxybutyrate-co-hydroxyvalerate as solid slow-releasing source of electron donors for the reductive dechlorination of 1,2-dichloroethane in-situ”, International Biodeterioration & Biodegradation, 86, 278e285.