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Polyhydroxyalkanoates

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Polyhydroxyalkanoates are polymers produced in nature by bacterial fermentation of sugar or lipids.
PHA is synthesized by bacteria under natural conditions (up to 30% of the dry weight of the bacteria), and up to 90% polymer by weight in dry bacteria if the fermentation conditions are carefully controlled, limiting oxygen and nitrogen.
PHA is produced by a 2 stage culture procedure. In the first stage, bacteria are provided with rich medium, allowing them to reproduce high cell densities. The bacterial cells are grown until a specific cell mass concentration is reached without nutrient limitation. The bacteria is then shifted to a medium deficient in nitrogen (a condition that favours storage of the polymer). During this nutrient limitation

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