Up-Cycling of PET (Polyethylene Terephthalate) to the Biodegradable Plastic PHA (Polyhydroxyalkanoate)

School of Biomolecular and Biomedical Sciences, Centre for Synthesis and Chemical Biology, National University of Ireland, University College Dublin, Belfield, Dublin 4, Republic of Ireland.
Environmental Science and Technology (Impact Factor: 5.33). 11/2008; 42(20):7696-701. DOI: 10.1021/es801010e
Source: PubMed


The conversion of the petrochemical polymer polyethylene terephthalate (PET) to a biodegradable plastic polyhydroxyalkanoate (PHA) is described here. PET was pyrolised at 450°C resulting in the production of a solid, liquid, and gaseous fraction. The liquid and gaseous fractions were burnt for energy recovery, whereas the solid fraction terephthalic acid (TA) was used as the feedstock for bacterial production of PHA. Strains previously reported to grow on TA were unable to accumulate PHA. We therefore isolated bacteria from soil exposed to PET granules at a PET bottle processing plant. From the 32 strains isolated, three strains capable of accumulation of medium chain length PHA (mclPHA) from TA as a sole source of carbon and energy were selected for further study. These isolates were identified using 16S rDNA techniques as P. putida (GO16), P. putida (GO19), and P. frederiksbergensis (GO23). P. putida GO16 and GO19 accumulate PHA composed predominantly of a 3-hydroxydecanoic acid monomer while P. frederiksbergensis GO23 accumulates 3-hydroxydecanoic acid as the predominant monomer with increased amounts of 3-hydroxydodecanoic acid and 3-hydroxydodecenoic acid compared to the other two strains. PHA was detected in all three strains when nitrogen depleted below detectable levels in the growth medium. Strains GO16 and GO19 accumulate PHA at a maximal rate of approximately 8.4 mg PHA/l/h for 12 h before the rate of PHA accumulation decreased dramatically. Strain GO23 accumulates PHA at a lower maximal rate of 4.4 mg PHA/l/h but there was no slow down in the rate of PHA accumulation over time. Each of the PHA polymers is a thermoplastic with the onset of thermal degradation occurring around 308°C with the complete degradation occurring by 370°C. The molecular weight ranged from 74 to 123 kDa. X-ray diffraction indicated crystallinity of the order of 18-31%. Thermal analysis shows a low glass transition (-53°C) with a broad melting endotherm between 0 and 45°C.

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    • "Pseudomonas is a promising host for biotechnology with a wide variety of possible products including biodegradable polymers (Ward et al., 2006; Goff et al., 2007; Kenny et al., 2008; Guzik et al., 2014; Tiso et al., 2015). Specific opportunities may be found in the increasing bioplastic and biosurfactant markets. "

    Full-text · Article · Sep 2015 · Microbial Biotechnology
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    • "Since ancient times, microorganisms have been used to produce bread, wine and dairy products in order to improve the quality of food and its nutrients. Today, microbes are utilized for the manufacture of a wide variety of fine or bulk chemicals including antibiotics [1,2], vitamins [3], biofuels [4,5], biodegradable and biocompatible plastics from waste [6] and terpene-based drugs [7,8]. Originally, the choice for a production host was dictated by the ability of the organism to produce the desired compounds, but in most cases the concentration of the chemicals of interest was not sufficient to cover the market demand. "
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    ABSTRACT: Background The red yeast Xanthophyllomyces dendrorhous is a natural producer of the carotenoid astaxanthin. Because of its high flux, the native terpene pathway leading to the production of the tetraterpene is of particular interest as it can be redirected toward the production of other terpene compounds. The genetic tools for the transformation of the yeast with the concurrent knock-out of genes involved in the astaxanthin biosynthesis are made available and here we show that the production of the sesquiterpene α-cuprenene is possible in mutant strains of X. dendrorhous transformed with the Cop6 gene originating from the fungus Coprinus cinereus. For the evaluation of the production levels, we chose to express the same gene and analyze the accumulation of α-cuprenene in Escherichia coli and Saccharomyces cerevisiae, as well. Here we propose that X. dendrorhous is a candidate in the search for the potential platform organism for the production of terpenes. Results All three X. dendrorhous mutants functionally express the Cop6 gene and accumulate α-cuprenene. The production of α-cuprenene in the red yeast reached 80 mg/L, which represents a far higher concentration compared to the levels obtained in the E. coli and S. cerevisiae mutants. At this expression levels the pool of terpene precursors has not become a limiting factor in the X. dendrorhous mutants since the expression of the Cop6 gene in the genomic rDNA of the yeast allows production of both α-cuprenene and astaxanthin without affecting the growth or the accumulation levels of both compounds. Conclusions We have shown that X. dendrorhous can produce α-cuprenene, and the results here presented, next to the capability of accumulating at least two more non-native sesquiterpenes, demonstrates the high potential of this yeast to become an interesting terpene-based drugs producer.
    Full-text · Article · Feb 2013 · Microbial Cell Factories
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    • "After successfully establishing that the isolate TN301 can accumulate mcl-PHA from naphthalene and glucose (Fig. 1), the strain was phenotypically and taxonomically identified as a species of the Pseudomonas genus. The most commonly isolated genus with aromatic hydrocarbon degradative capabilities is Pseudomonas (Zylstra and Gibson 1989; Ramos et al. 1995; Bastiaens et al. 2000; Popp et al. 2006; Kenny et al. 2008). Although the highest homology of 16S rDNA was with P. plecoglossicida L21, the nonfluorescent pseudomonad isolated from fish (Izumi et al. 2007), phenotypically TN301 was more similar to P. putida F1 and P. putida GB-1, and it also shared high 16S rDNA sequence homology with these strains (99% identity with 99% coverage). "
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    ABSTRACT: The aim of this study was to convert numerous polyaromatic and monoaromatic hydrocarbons into biodegradable polymer medium-chain-length polyhydroxyalkanoate (mcl-PHA). Using naphthalene enrichment cultivation method, we have isolated seven bacterial strains from the river sediment exposed to petrochemical industry effluents. In addition to naphthalene, all seven strains could utilize between 12 and 17 different aromatic substrates, including toluene, benzene and biphenyl. Only one isolate that was identified as Pseudomonas sp. TN301 could accumulate mcl-PHA from naphthalene to 23% of cell dry weight. Owing to poor solubility, a method of supplying highly hydrophobic polyaromatic hydrocarbons to a culture medium was developed. The best biomass and mcl-PHA yields were achieved with the addition of synthetic surfactant Tween 80 (0.5 g l(-1)). We have shown that Pseudomonas sp. TN301 can accumulate mcl-PHA from a wide range of polyaromatic and monoaromatic hydrocarbons, and mixtures thereof, while it could also accumulate polyphosphates and was tolerant to the presence of heavy metal (100 mmol l(-1) cadmium and 20 mmol l(-1) nickel). A new Pseudomonas strain was isolated and identified with the ability to accumulate mcl-PHA from a variety of aromatic hydrocarbons. This study is the first report on the ability of a bacterial strain to convert a range of polyaromatic hydrocarbon compounds to the biodegradable polymer (mcl-PHA). Mcl-PHA is gaining importance as a promising biodegradable thermoelastomer, and therefore, isolation of new producing strains is highly significant. Furthermore, this strain has the ability to utilize a range of hydrocarbons, which often occur as mixtures and could potentially be employed in the recently described efforts to convert waste materials to PHA.
    Full-text · Article · May 2012 · Journal of Applied Microbiology
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