title: The conversion of BTEX compounds by single and defined mixed cultures to medium-chain-length polyhydroxyalkanoate.
abstract: Here, we report the use of petrochemical aromatic hydrocarbons as a feedstock for the biotechnological conversion into valuable biodegradable plastic polymers--polyhydroxyalkanoates (PHAs). We assessed the ability of the known Pseudomonas putida species that are able to utilize benzene, toluene, ethylbenzene, p-xylene (BTEX) compounds as a sole carbon and energy source for their ability to produce PHA from the single substrates. P. putida F1 is able to accumulate medium-chain-length (mcl) PHA when supplied with toluene, benzene, or ethylbenzene. P. putida mt-2 accumulates mcl-PHA when supplied with toluene or p-xylene. The highest level of PHA accumulated by cultures in shake flask was 26% cell dry weight for P. putida mt-2 supplied with p-xylene. A synthetic mixture of benzene, toluene, ethylbenzene, p-xylene, and styrene (BTEXS) which mimics the aromatic fraction of mixed plastic pyrolysis oil was supplied to a defined mixed culture of P. putida F1, mt-2, and CA-3 in the shake flasks and fermentation experiments. PHA was accumulated to 24% and to 36% of the cell dry weight of the shake flask and fermentation grown cultures respectively. In addition a three-fold higher cell density was achieved with the mixed culture grown in the bioreactor compared to shake flask experiments. A run in the 5-l fermentor resulted in the utilization of 59.6 g (67.5 ml) of the BTEXS mixture and the production of 6 g of mcl-PHA. The monomer composition of PHA accumulated by the mixed culture was the same as that accumulated by single strains supplied with single substrates with 3-hydroxydecanoic acid occurring as the predominant monomer. The purified polymer was partially crystalline with an average molecular weight of 86.9 kDa. It has a thermal degradation temperature of 350 degrees C and a glass transition temperature of -48.5 degrees C.
authors.affiliation: School of Biomolecular and Biomedical Sciences, Ardmore House, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Jasmina
authors.initials: J
authors.lastname: Nikodinovic
authors.forename: Shane T
authors.initials: ST
authors.lastname: Kenny
authors.forename: Ramesh P
authors.initials: RP
authors.lastname: Babu
authors.forename: Trevor
authors.initials: T
authors.lastname: Woods
authors.forename: Werner J
authors.initials: WJ
authors.lastname: Blau
authors.forename: Kevin E
authors.initials: KE
authors.lastname: O'Connor
mesh_terms: D018533:Biomass; D001711:Biotransformation; D005285:Fermentation; D006841:Hydrocarbons, Aromatic / Q000378:metabolism*; D054813:Polyhydroxyalkanoates / Q000737:chemistry / Q000378:metabolism*; D016958:Pseudomonas putida / Q000254:growth & development / Q000378:metabolism*
chemical_list: D006841:Hydrocarbons, Aromatic; D054813:Polyhydroxyalkanoates