polyhydroxypropionate

Polyhydroxypropionate (PHP) is a family of biopolymers consisting of hydroxypropionate units, the best known member being poly(3-hydroxypropionate) or P3HP. PHPs are part of the broader class of polyhydroxyalkanoates (PHAs), natural polyesters produced by a variety of bacteria and some archaea as intracellular storage compounds. They are generally biodegradable and biocompatible, making them of interest for sustainable plastics and biomedical materials.

Structure and variants: PHPs can form both homopolymers, composed entirely of 3-hydroxypropionate units, and copolymers that incorporate other hydroxyalkanoate units. The chemical composition and molecular weight influence crystallinity, flexibility, and thermal behavior, allowing tuning of material properties for different applications.

Biosynthesis and production: In microorganisms, PHPs arise through specific metabolic pathways that channel carbon into hydroxypropionate-CoA derivatives, which are then polymerized by PHA synthases (PhaC). Engineered bacterial strains often employ malonyl-CoA–related routes, sometimes using enzymes such as malonyl-CoA reductase to generate 3-hydroxypropionyl-CoA for polymerization. Growth conditions, feedstocks (for example, sugars or glycerol), and genetic modifications are optimized to increase polymer yield and molecular weight.

Occurrence and applications: Native producers have been identified in various bacteria and archaea, though industrial production primarily uses recombinant strains. Applications focus on biodegradable plastics, packaging materials, and biomedical devices or scaffolds, where biocompatibility and controlled degradation are advantageous. Ongoing research aims to expand monomer diversity, improve process efficiency, and tailor mechanical properties.

See also: polyhydroxyalkanoates, biopolymers, biodegradable plastics.