Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Polyhydroxybutyrate (PHB) is a type of biopolymer produced by certain bacteria as an energy storage compound. It is a member of the polyhydroxyalkanoate (PHA) family and serves as an intracellular carbon reserve.
5 Must Know Facts For Your Next Test
PHB is synthesized by various prokaryotic microorganisms such as Cupriavidus necator and Bacillus megaterium.
PHB accumulates in the cytoplasm of bacterial cells as granules when there is an excess of carbon sources.
The synthesis of PHB involves enzymes like beta-ketothiolase, acetoacetyl-CoA reductase, and PHB synthase.
PHB has properties similar to plastics but is biodegradable, making it environmentally friendly.
In nutrient-limited conditions other than carbon, bacteria metabolize PHB to derive energy and carbon.
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Related terms
Polyhydroxyalkanoates (PHA): A family of biodegradable polymers produced by microorganisms as storage materials.
Cupriavidus necator: A bacterium known for its ability to produce large amounts of polyhydroxybutyrate.
Biodegradable Plastics: Plastics that can be broken down by microorganisms into water, carbon dioxide, and biomass.