Connecting Deep Eutectic Solvents and Polyhydroxyalkanoates: Feedstock Pretreatment, Polymer Recovery, Material Modification and End-of-Life Valorization

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Abstract
Polyhydroxyalkanoates (PHAs) are bio-based and biodegradable polyesters whose wider use is constrained by production costs, downstream recovery challenges and material limitations. This review critically examines deep eutectic solvents (DESs) across four stages of the PHA value chain: feedstock pretreatment, intracellular polymer recovery, material modification, and end-of-life valorization. Available evidence shows that DES-assisted pretreatment can improve delignification and saccharification, although direct integration with PHA fermentation remains limited. Hydrophobic DESs (HDESs), including natural formulations (NADESs), have yielded high-purity PHA, but recovery efficiency, solvent residues, antisolvent requirements and preservation of molecular weight remain challenges. In PHA-based materials, DESs can function as compatibilizers, plasticizers, fiber-treatment media and carriers of functional compounds, with effects depending strongly on DES composition and processing conditions. Direct DES-mediated PHA recycling remains largely unexplored, whereas PHA-derived hydroxyalkanoic acids have been used to prepare new eutectic systems. Most studies have examined individual applications at laboratory scale, and the benefits of integrating DESs across successive PHA processing stages remain to be demonstrated. Future research should prioritize process integration, solvent recovery and reuse, polymer quality and scale-up. Comparative techno-economic and life-cycle assessments are also needed to establish whether these approaches offer environmental and economic advantages over conventional technologies.
Funding Information
  • Ministry of Science, Technological Development and Innovation of the Republic of Serbia (451-03-33/2026-03/200134)
  • CEEC IND program (2022.04909.CEECIND/CP1725/CT0014)
  • FCT—Fundação para a Ciência e a Tecnologia, I. P. (UID/50006/2023)

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