Polyhydroxyalkanoates biosynthesis mechanisms

Mittendorf V, Kriiger N, Steinbiichel A, Poirier Y (1998) Biosynthesis of medium-chain-length polyhydroxyalkanoates in transgenic Arahidopsis plants expressing the PhaCl and PhaC2 synthases from Pseudomonas aeruginosa. In Steinbiichel A (ed) Biochemical principles and mechanisms of biosynthesis and biodegradation of polymers. Wiley-VCH, Weinheim, p 368... 

All these polyesters are produced by bacteria in stressed conditions in which tlrey are deprived of some essential component for their normal metabolic processes. Under normal conditions of balanced growth the bacteria would utilize any substrate for energy and growth, whereas under stressed conditions they utilize any suitable substrate to produce polyesters as reserve material. When the bacteria can no longer subsist on the organic substrate due to depletion, they consume the reserve for energy and food for survival. Similarly, upon removal of the stress, the reserve is consumed and normal activities resumed. This cycle is utilized to produce the polymers which are harvested at maximum cell yield. This process is outlined schematically below ( Lenz), and in more detail in the paper by Steinbuchel (1991) on the mechanism of biosynthesis of polyhydroxyalkanoates. 

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