Polyhydroxyalkanoate (PHA) purification through dilute aqueous ammonia digestion at elevated temperatures

Anna Burniol-Figols, Ioannis V. Skiadas, Anders E. Daugaard, Hariklia N. Gavala*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

BACKGROUND
Purification of polyhydroxyalkanoates (PHA) is a challenging step, given the difficulty of achieving high PHA purity, while maintaining polymer integrity, in a sustainable and cost‐efficient manner. This study evaluated the potential of dilute ammonia digestion as a method to purify PHA from mixed microbial consortia.

RESULTSDigestion temperatures were critical to the obtainable purity and the amount of recovered PHA. At temperatures below 75 °C (regardless of the incubation time and ammonia concentration), a low PHA recovery (down to 65 %) and no increase in purity was observed. By increasing the temperature above 75 °C, a significantly higher PHA purity and higher recovery (above 90 %) could be achieved. Temperatures maximizing the purity (140 °C) led to a detrimental reduction in the molar mass of the isolated PHA, but the use of a sonication pre‐treatment enabled to increase the purity at temperatures leading to limited molar mass loss (75‐115 °C). The impurities still present in the recovered PHA did not compromise its thermal stability, and no significant degradation occurred during melting of PHA with 86 % purity (comparably to pure chloroform‐extracted PHA). Conversely, PHA recovered through H2SO4 digestion underwent severe degradation during melting, despite presenting higher purity (98 %).

CONCLUSIONS
High PHA purity, recovery and thermal stability can be obtained with dilute ammonia digestion. These observations, combined with the possibility of reusing ammonia within the process, make this method a promising approach for a more sustainable purification of PHA.
Original languageEnglish
JournalJournal of Chemical Technology and Biotechnology
Volume95
Issue number5
Pages (from-to)1519-1532
ISSN0268-2575
DOIs
Publication statusPublished - 2020

Keywords

  • Biodegradable
  • Downstream
  • Environmental biotechnology
  • Purification
  • Waste treatment and waste minimization
  • Bioprocesses

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