Quantification of Polyhydroxyalkanoates

Polyhydroxyalkanoate(s) (PHA) are a group of polymers made up of a broad range of monomers. The variety of monomers and the percentage composition inflnence the material properties, contributing to the development of different applications. This highlights the importance of determining and quantifying the types and composition of the monomers. 

A faster and more sensitive method was developed by Williamson and Wilkinson [3] which spectrophotometrically determined PHA based on the biomass turbidity after treatment with sodium hypochlorite. This method suffered from the need to be customised for different microorganisms and was only able to measure the polymer in the native lipid PHA granules. 

Slepecky and Law [4], and Law and Slepecky [2] devised a spectrophotometric assay of P(3HB) by quantitatively converting P(3HB) to crotonic acid, using a heating process and concentrated 

PHA quantification using gas chromatography (GC) was introduced by Braunegg and co-workers [8]. It was considered to be a major advance in the development of the PHA quantification method because it provided an accurate and more reproducible analytical measurement. Acidic hydrolysis of the microbial biomass was found to be superior to alkaline hydrolysis, as used by Wallen and Rohwedder [9], since the former resulted in the formation of only one methyl ester and the latter resulted in two methyl esters for a single component. Moreover, quantification using GC could be improved by the use of an internal standard. This method was found to show better performance compared with most of the methods previously used hence, this method was adapted and used by many authors [10-14]. 

The use of nuclear magnetic resonance (NMR) in quantifying PHA was fully explored starting from 1980 onwards. NMR is a non-invasive approach, which can be accurately used to determine the different types of PHA consisting of a variety of chemical structures. 

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Gorenflo V, Steinbiichel A, Marose S, Rieseberg M, Scheper T (1999) Quantification of bacterial polyhydroxyalkanoic acids by Nile red staining. Appl Microbiol Biotechnol 51 765-772... 

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