A Two Step Chemo-biotechnological Conversion of Polystyrene to a Biodegradable Thermoplastic

• Published in: Environmental science & technology 2006-04, Vol.40 (7), p.2433-2437
• Main Authors: Ward, Patrick G, Goff, Miriam, Donner, Matthias, Kaminsky, Walter, O'Connor, Kevin E
• Format: Article
• Language: English
• Subjects: Applied sciences; Biodegradable materials; Biodegradation, Environmental; Biological and medical sciences; Biological treatment of sewage sludges and wastes; Biotechnology; Environment and pollution; Exact sciences and technology; Fermentation; Fluidized bed reactors; Fundamental and applied biological sciences. Psychology; General treatment and storage processes; Industrial applications and implications. Economical aspects; Plastics - metabolism; Pollution; Polymer industry, paints, wood; Polystyrene; Polystyrenes - metabolism; Pseudomonas putida; Pseudomonas putida - metabolism; Technology of polymers; Thermoplastics; Waste treatment; Wastes
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es0517668

A novel approach to the recycling of polystyrene is reported here; polystyrene is converted to a biodegradable plastic, namely polyhydroxyalkanoate (PHA). This unique combinatorial approach involves the pyrolysis of polystyrene to styrene oil, followed by the bacterial conversion of the styrene oil to PHA by Pseudomonas putida CA-3 (NCIMB 41162). The pyrolysis (520 °C) of polystyrene in a fluidized bed reactor (Quartz sand (0.3−0.5 mm)) resulted in the generation of an oil composed of styrene (82.8% w/w) and low levels of other aromatic compounds. This styrene oil, when supplied as the sole source of carbon and energy allowed for the growth of P. putida CA-3 and PHA accumulation in shake flask experiments. Styrene oil (1 g) was converted to 62.5 mg of PHA and 250 mg of bacterial biomass in shake flasks. A 1.6-fold improvement in the yield of PHA from styrene oil was achieved by growing P. putida CA-3 in a 7.5 liter stirred tank reactor. The medium chain length PHA accumulated was comprised of monomers 6, 8, and 10 carbons in length in a molar ratio of 0.046:0.436:1.126, respectively. A single pyrolysis run and four fermentation runs resulted in the conversion of 64 g of polystyrene to 6.4 g of PHA.