Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025
Definition
Poly-β-hydroxybutyrate (PHB) is a type of biopolymer produced by certain bacteria as a form of energy storage. It is a biodegradable plastic with properties similar to petrochemical-derived plastics.
PHB is synthesized by microorganisms such as Alcaligenes eutrophus and Bacillus megaterium.
It accumulates in bacterial cells in the form of granules, which can be observed under a microscope.
PHB production is typically initiated under conditions of nutrient limitation, particularly nitrogen or phosphorus deficiency, while excess carbon sources are available.
The polymer is biodegradable and compostable, making it an environmentally friendly alternative to traditional plastics.
PHB can be extracted from bacterial cells through solvent extraction methods and used in various applications like packaging, agriculture, and medical devices.
Related terms
Biodegradable Plastics: Plastics that can be decomposed by the action of living organisms, usually bacteria.
Alcaligenes eutrophus: A type of bacteria known for its ability to produce polyhydroxyalkanoates including PHB.
Nutrient Limitation: A condition where specific nutrients are scarce, triggering certain microbial metabolic processes such as PHB synthesis.