Disassembly and reassembly of polyhydroxyalkanoates: Recycling through abiotic depolymerization and biotic repolymerization

• Published in: Bioresource technology Vol. 170; no. C; pp. 167 - 174
• Main Authors: Myung, Jaewook, Strong, Nathaniel I., Galega, Wakuna M., Sundstrom, Eric R., Flanagan, James C.A., Woo, Sung-Geun, Waymouth, Robert M., Criddle, Craig S.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2014; Elsevier
• Subjects: 3-Hydroxybutyric Acid - biosynthesis; 3-Hydroxybutyric Acid - chemistry; Biological and medical sciences; Bioreactors; Biotechnology - methods; Crotonates - chemistry; Fundamental and applied biological sciences. Psychology; Gas Chromatography-Mass Spectrometry; Hot Temperature; Models, Biological; Molecular Structure; PHB; PHBV; Polyhydroxyalkanoate; Polyhydroxyalkanoates - biosynthesis; Polyhydroxyalkanoates - chemical synthesis; Polyhydroxyalkanoates - chemistry; Polymerization; Polyphosphate; Polyphosphates - chemistry; Recycling; Recycling - methods; PHBV; Polyphosphate; PHB; Recycling; Polyhydroxyalkanoate; Depolymerization; Alkanoate(hydroxy) polymer; Environmental factor; Polyphosphates; Abiotic factor; Biotic factor
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2014.07.105

•Base depolymerizes polyhydroxyalkanoates (PHAs) to hydroxyacids and alkenoates.•Thermal treatment depolymerizes PHAs to alkenoates.•A microbial enrichment repolymerizes PHAs from hydroxyacids and alkenoates.•Nitrogen-limited cells produce high quality PHA homopolymer and copolymer.•Polyphosphate hydrolysis accompanies repolymerization. An abiotic–biotic strategy for recycling of polyhydroxyalkanoates (PHAs) is evaluated. Base-catalyzed PHA depolymerization yields hydroxyacids, such as 3-hydroxybutyrate (3HB), and alkenoates, such as crotonate; catalytic thermal depolymerization yields alkenoates. Cyclic pulse addition of 3HB to triplicate bioreactors selected for an enrichment of Comamonas, Brachymonas and Acinetobacter. After each pulse, poly(3-hydroxybutyrate) (P3HB) transiently appeared: accumulation of P3HB correlated with hydrolysis of polyphosphate; consumption of P3HB correlated with polyphosphate synthesis. Cells removed from the cyclic regime and incubated with 3HB under nitrogen-limited conditions produced P3HB (molecular weight>1,000,000Da) at 50% of the cell dry weight (<8h). P3HB also resulted from incubation with acetate, crotonate, or a mixture of hydrolytic depolymerization products. Poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) resulted from incubation with valerate or 2-pentenoate. A recycling strategy where abiotic depolymerization of waste PHAs yields feedstock for customized PHA re-synthesis appears feasible, without the need for energy-intensive feedstock purification.