Glycerol is an effective carbon source for the production of scl- and mcl-polyhydroxyalkanoates (PHAs) by Pseudornonas spp. P. mediterranea 9.1 (CFBP 5447) synthesizes an amorphous mcl-PHA when grown on crude glycerol, whereas on both reagent grade (RG) and partially refined (PR) glycerol, it produces two very similar distinctive mcl-PHAs with the unusual property of producing, with the appropriate treatment, a transparent film. Mcl-PHAs recovered after biomass extraction have an average molecular weight of approximately 56,000/63,000 Da. The monomer composition and physicochemical properties of such mcl-PHAs suggest their potential application as a softener of biopolymeric blends for food packaging and medical devices. (C) 2014 Elsevier B.V. All rights reserved.