Polyhydroxyalkanoates

Polyhydroxyalkanoates or PHAs are polyesters produced in nature by numerous microorganisms, including through bacterial fermentation of sugars or lipids.

[4] To induce PHA production in a laboratory setting, a culture of a micro-organism such as Cupriavidus necator can be placed in a suitable medium and fed appropriate nutrients so that it multiplies rapidly.

[5] However, the prevalence of PHA production within either a mono-culture or a set of mixed-microbial organisms can also be dependent on overall nutrient limitation, not just macro elements.

The two classes of PHA synthases differ in the specific use of hydroxy fatty acids of short or medium chain length.

The simplest and most commonly occurring form of PHA is the fermentative production of poly-beta-hydroxybutyrate [poly(3-hydroxybutyrate), P(3HB)], which consists of 1000 to 30000 hydroxy fatty acid monomers.

In the industrial production of PHA, the polyester is extracted and purified from the bacteria by optimizing the conditions of microbial fermentation of sugar, glucose, or vegetable oil.

Several companies are working to develop methods of producing PHA from waste water, including Veolia subsidiary Anoxkaldnes.

Furthermore, active research is being carried out for the biotransformation "upcycling" of plastic waste (e.g., polyethylene terephthalate and polyurethane) into PHA using Pseudomonas putida bacteria.

In June 2005, US company Metabolix, Inc. received the US Presidential Green Chemistry Challenge Award (small business category) for their development and commercialisation of a cost-effective method for manufacturing PHAs.

[18] There are potential applications for PHA produced by micro-organisms[2] within the agricultural,[19] medical and pharmaceutical industries, primarily due to their biodegradability.