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.

PHBV/cellulose nanofibrils composites obtained by solution casting and electrospinning process

“…Some pores were caused by the fast evaporation of the solvent due to the high volatility during the drying process at 153 °C [24]. Figure 3b, revealed a homogeneous morphology without the presence of beads, indicating that the addition of CNFs in the polymer solution improved the electrospinning process, because addition of CNFs tends to increase the viscosity of the solution, which decreases droplet formation at the needle tip, preventing the formation of beads.…”

Identification of Four Polyhydroxyalkanoate Structural Genes in Synechocystis cf. salina PCC6909: In silico Evidences

“…Among other biomaterials, polyhydroxyalkanoates (PHAs) have attractive physical properties such as thermoplasticity, low crystallinity and high UV-stability [3,4]. These characteristics can be tuned for tailor-made applications like elastic coatings for disposable items [5]. Moreover, biodegradability ensures lower disposal costs and brings environmental advantages [1,2,[6][7][8].…”

Potential of polyhydroxyalkanoate (PHA) polymers family as substitutes of petroleum based polymers for packaging applications and solutions brought by their composites to form barrier materials

“…PHBV-bacterial cellulose nanowhiskers (BCNW) nanocomposite with various hydroxyvalerate contents was studied and characterized by Martinez-Sanz et al [27]. PHBV samples which contain 7.3 mol% valerate (PHBV7) and 40 mol% valerate (PHBV40) were used in the study.…”

“…A bad dispersion of fillers can affect negatively the mechanical properties and thus a work on formulation, by adding plasticizer or binding agent for instance, may therefore become necessary. The increase in hydroxyvalerate content conducts to an increase in permeability values [27,29] whereas it is needed to reduce material brittleness.…”