Fourier transform infrared spectroscopy for screening and quantifying production of PHAs by Pseudomonas grown on sodium octanoate

Poly(hydroxyalkanoates) PHAs are synthesized by many bacteria as inclusion bodies and their biodegradability and structural diversity have been studied with a view to their potential application as biodegradable materials. A method based on FT-IR was developed to carry out rapid qualitative and quantitative analysis of PHAs in Pseudomonas, when they were grown on sodium octanoate. Using absorbance of the ester band of PHAs, a rapid method was reported to distinguish PHB and PHO and to determine polymer content in intact bacteria. Relative areas in which the C=O area was normalized to the area of the peak representing the amid group (1656 cm(-1)) characteristic of bacteria were calibrated to the polymer content which was determined after solvent extraction. Polymer contents vary from 0% to 53% and depend on the nature of the bacteria. Among 27 strains of Pseudomonas belonging to the rRNA homology group I, a very low amount of bacteria were able to produce PHB. The majority of strains were able to produce a copolymer, PHO, in which the major constituent unit is 3-hydroxyoctanoate. The FT-IR results were further confirmed by gas chromatography analysis after methanolysis of polymer, but FT-IR method requires less preparation of sample than gas chromatography and it is very useful for screening a large variety of Pseudomonas.