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In the present study, we used microwave energy instead of conventional heating to transform poly-3-hydroxybutyrate (PHB) into methyl 3-hydroxybutyrate (Me-3HB) in acidified methanol (H2SO4, 10%, v/v) mixture in less than 4 min at 10% microwave power. The microwave assisted method was then applied to analyze PHB produced by Alcaligenes latus. The PHB content in the biomass determined using microwave heating was comparable to the amount found by conventional heating. Moreover, the new esterification method was at least 50 times faster than the conventional method, affording a significant saving of time and energy.

Biopolymers such as poly(hydroxyalkanoates) (PHAs) have received much attention due to their physico-chemical properties, biodegradability, and biocompatibility that make them good candidates for industrial and medical applications. Produced by some microorganisms PHAs accumulate within the cells of these organisms. The optimization of microbial processes to produce PHAs at a lower cost requires rapid and accurate techniques for quantification of the biopolymer in biomass. The present study describes a method based on solid-phase microextraction (SPME) coupled to gas chromatography (GC) for the determination of poly(3-hydroxybutyrate) (PHB) in Alcaligenes latus cells. First PHB was depolymerized by either methanolic or hydrolytic digestion into methyl 3-hydroxybutyrate (Me-3-HB) or crotonic acid (CA), respectively. The resulting analytes were then subjected to analysis by headspace SPME/GC with flame ionization detection (FID). The two depolymerization/SPME/GC-FID methods were optimized and applied to the analysis of PHB in bacterial biomass harvested from a fermentation process that uses A. latus. Results were compared with those obtained using GC-FID analysis of MeOH/CHCl(3) digested samples. Excellent agreement was found between the three methods but the two SPME-based methods were environmentally friendly and easier to perform.