International Journal of Biological Macromolecules 65 (2014) 89–96 Contents lists available at ScienceDirect International Journal of Biological Macromolecules jo ur nal homep age: www.elsevier.com/locate/ijbiomac Production of filmable medium-chain-length polyhydroxyalkanoates produced from glycerol by Pseudomonas mediterranea Francesco Pappalardo a,∗ , Manuela Fragalà a , Placido G. Mineo b,c , Arcangelo Damigella a , Antonino F. Catara a , Rosa Palmeri a , Antonio Rescifina d,∗ a Science and Technology Park of Sicily, Blocco Palma I stradale V. Lancia 57, 95123 Catania, Italy b Dipartimento di Scienze Chimiche and I.N.S.T.M. UdR of Catania, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy c CNR-IPCF Istituto per i Processi Chimico Fisici, Viale Ferdinando Stagno D’Alcontres 37, 98158 Messina, Italy d Dipartimento di Scienze del Farmaco, Università di Catania, Viale Andrea Doria 6, 95125 Catania, Italy a r t i c l e i n f o Article history: Received 23 September 2013 Received in revised form 17 December 2013 Accepted 4 January 2014 Available online 10 January 2014 Keywords: Pseudomonas mediterranea mcl-PHA Glycerol a b s t r a c t Glycerol is an effective carbon source for the production of scl- and mcl-polyhydroxyalkanoates (PHAs) by Pseudomonas 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 treat- ment, 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. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Polyhydroxyalkanoates are biodegradable polymers, with ther- moplastic, elastomeric and adhesive properties comparable to synthetic polyesters, upon composition of the monomer unit, the microorganism used in fermentation, as well as the nature of the carbon source [1,2]. They are widely distributed in nature and accumulate in various bacteria as intracellular carbon and energy storage materials in the form of water-insoluble granules [3]. Since they can be produced from renewable carbon resources, PHAs can play a positive role in agriculture, the environment and the econ- omy, contributing to the conservation of finite fossil resources, such as mineral oil and coal, and are neutral with regard to CO 2 emissions [4]. Based on their repeat unit compositions, PHAs belong to two main groups and blends: short-chain-length (scl-) PHAs with hydroxy fatty acid (HFA) repeat units, 3–5 carbon chain length (C3–C5), and medium-chain-length (mcl-) PHAs with C6 and longer repeat units. In general, scl-PHAs are thermoplastics with vari- ous degrees of crystallinity and are brittle and stiff [5]; whereas mcl-PHAs with low crystallinity, low glass transition tempera- tures, low tensile strength and high elongation to break ratios, are ∗ Corresponding authors. Tel.: +39 095 738 50 17. E-mail address: arescifina@unict.it (A. Rescifina). amorphous flexible elastomeric polymers with adhesive proper- ties. Owing to these favorable characteristics, mcl-PHA and their copolymers are attracting attention for industrial and, particularly, biomedical applications where flexible biocompatible biomaterials are required [5,6]. More than 150 different known monomers can be combined within this family to yield materials with extremely differ- ent properties and characteristics depending on the side chain length and on the substrate the producer bacteria are fed [7]. In spite of their potential for replacing petroleum-based poly- mers in many industrial applications, the introduction of PHAs onto the worldwide market is currently limited due to their production costs which are higher than synthetic alternatives [8,9]. Moreover, several techniques involved in the process remain an additional limiting factor, unless oil prices rise, making PHAs from renewable resources more competitive. There is therefore a growing interest in the development of novel microbial processes and products with reduced production costs [8,9]. Many bacteria, isolated from the natural environment, have been tested and many have been recently re-constructed to produce PHAs [10]. These include various species of Pseudomon- ads belonging to rRNA-DNA homology group I, which are known as microbial producers of PHAs built from hydroxyl-acyl-CoA deriva- tives via different metabolic pathways of the bacterial fermentation of sugar or lipids [11]. 0141-8130/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ijbiomac.2014.01.014