Medium chain-length polyhydroxyalkanoates (mPHAs) are flexible elastomeric biopolymers with valuable properties for biomedical applications like artificial arteries and other medical implants. However, an environmentally friendly and high productivity process together with the tuning of the mechanical and biological properties of mPHAs are mandatory for this purpose. Here, for the first time, a melt processing technique was applied for the preparation of bionanocomposites starting from poly(3-hydroxyoctanoate) (PHO) and bacterial cellulose nanofibers (BC). The incorporation of only 3 wt % BC in PHO improved its thermal stability with 25 °C and reinforced it, increasing the Young's modulus with 76% and the tensile strength with 44%. The percolation threshold calculated with the aspect ratio of the fibers after melt processing was very low and close to 3 wt %. We showed that this bionanocomposite is able to preserve the ductile behavior during storage, no important aging being noted between 3 h and one month after compression-molding. Moreover, this study is the first to investigate the melt processability of PHO nanocomposite for tube extrusion. In addition, biocompatibility study showed no proinflammatory immune response and better cell adhesion for PHO/BC nanocomposite with 3 wt % BC and demonstrated the high feasibility of this bionanocomposite for in vivo application of tissue-engineered blood vessels.
Medium-chain-length polyhydroxyalkanoates (mcl-PHAs) are naturally produced by bacteria and accumulates in cytoplasm in the form of granules, in particular culture broth conditions. PHAs are biodegradable, biocompatible and have useful mechanical properties that recommend them for divers applications in various fields. In order to obtain mcl-PHAs of microbial origin we used two Pseudomonas spp. strains, namely Pseudomonas putida ICCF 391 and Pseudomonas fluorescens ICCF 392. Researches have focused the ability of these two strains to use structurally related or not related substrates, to obtain biopolymers with controlled composition, and growth the amount of PHAs in reproducible conditions. Moreover, bioprocess conditions for mcl-PHAs biosynthesis, fermentation broth processing, and polymers composition-were reproducible. As the results achieved with the two strains were similar, researches continued with Pseudomonas fluorescens strain, which is less studied regarding the potential of PHA biosynthesis. Were carried out (co) polymer films containing more than 85% PHO, as determined by GC-FID.
Abstract. Polyhydroxyalcanoates (PHAs) are specifically produced by a wide variety of bacteria, as an intracellular energy reserve in the form of homo-and copolymers of [R]-β-hydroxyalkanoic acids, depending on the C source used for microorganism growth, when the cells are grown under stressing conditions. In this paper we present microbiological accumulation of poly-3-hydroxyoctanoate (PHO) by using a consortium of bacterial strains, Pseudomonas putida and Bacillus subtilis, in a rate of 3:1, grown on a fermentation medium based on sodium octanoate as the sole carbon source. The experiments performed in the above mentioned conditions led to the following results: from 18.70 g sodium octanoate (7.72 g/L in the fermentation medium) used up during the bioprocess, 3.93-3.96 g/L dry bacterial biomass and 1.834 -1.884 g/L PHA, containing 85.83 -86.8% PHO, were obtained.
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