title: Characterization of polyhydroxyalkanoates synthesized from microbial mixed cultures and of their nanobiocomposites with bacterial cellulose nanowhiskers.
abstract: The present work reports on the production and characterization of polyhydroxyalkanoates (PHAs) with different valerate contents, which were synthesized from microbial mixed cultures, and the subsequent development of nanocomposites incorporating bacterial cellulose nanowhiskers (BCNW) via solution casting processing. The characterization of the pure biopolyesters showed that the properties of PHAs may be strongly modified by varying the valerate ratio in the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymer, as expected. Increasing the valerate content was seen to greatly decrease the melting temperature and enthalpy of the material, as well as its rigidity and stiffness, resulting in a more ductile behaviour. Additionally, the higher valerate PHA displayed higher permeability to water and oxygen and higher moisture sensitivity. Subsequently, BCNW were incorporated into both PHA grades, achieving a high level of dispersion for a 1 wt.-% loading, whereas some agglomeration took place for 3 wt.-% BCNW. As evidenced by DSC analyses, BCNW presented a nucleating effect on the PHA matrices. BCNW also increased the thermal stability of the polymeric matrices when properly dispersed due to strong matrix-filler interactions. Barrier properties were seen to depend on relative humidity and improved at low nanofiller loadings and low relative humidity.
authors.affiliation: Novel Materials and Nanotechnology Group, IATA, CSIC, Avda. Agustín Escardino, 7, Paterna 46980, Valencia, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Martínez-Sanz
authors.affiliation: Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, Rome 00185, Italy.
authors.forename: Marianna
authors.initials: M
authors.lastname: Villano
authors.affiliation: Biochemical Engineering Laboratory, Instituto de Biologia Experimental e Tecnológica, Lisbon, Portugal; CQFB-Requimte, FCT-UNL, Campus da Caparica, Caparica 2829-516, Portugal.
authors.forename: Catarina
authors.initials: C
authors.lastname: Oliveira
authors.affiliation: Biochemical Engineering Laboratory, Instituto de Biologia Experimental e Tecnológica, Lisbon, Portugal; CQFB-Requimte, FCT-UNL, Campus da Caparica, Caparica 2829-516, Portugal.
authors.forename: Maria G E
authors.initials: MG
authors.lastname: Albuquerque
authors.affiliation: Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, Rome 00185, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Majone
authors.affiliation: Biochemical Engineering Laboratory, Instituto de Biologia Experimental e Tecnológica, Lisbon, Portugal; CQFB-Requimte, FCT-UNL, Campus da Caparica, Caparica 2829-516, Portugal.
authors.forename: Maria
authors.initials: M
authors.lastname: Reis
authors.affiliation: Novel Materials and Nanotechnology Group, IATA, CSIC, Avda. Agustín Escardino, 7, Paterna 46980, Valencia, Spain.
authors.forename: Amparo
authors.initials: A
authors.lastname: Lopez-Rubio
authors.affiliation: Novel Materials and Nanotechnology Group, IATA, CSIC, Avda. Agustín Escardino, 7, Paterna 46980, Valencia, Spain. Electronic address: lagaron@iata.csic.es.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Lagaron
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D002152:Calorimetry, Differential Scanning; D002482:Cellulose / Q000378:metabolism* / Q000648:ultrastructure; D002849:Chromatography, Gas; D055119:Elastic Modulus; D006813:Humidity; D019344:Lactic Acid / Q000737:chemistry; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D010100:Oxygen / Q000737:chemistry; D010539:Permeability; D011091:Polyesters; D054813:Polyhydroxyalkanoates / Q000096:biosynthesis*; D011108:Polymers / Q000737:chemistry; D066244:Proton Magnetic Resonance Spectroscopy; D017550:Spectroscopy, Fourier Transform Infrared; D013718:Tensile Strength; D013818:Thermogravimetry; D014867:Water / Q000737:chemistry
chemical_list: D011091:Polyesters; D054813:Polyhydroxyalkanoates; D011108:Polymers; D014867:Water; D019344:Lactic Acid; C033616:poly(lactide); D002482:Cellulose; D010100:Oxygen