The Influence of Mineral Ions on the Microbial Production and Molecular Weight of Hyaluronic Acid

This study aimed to evaluate the influence of the culture medium supplementation with mineral ions, focusing on the growth of Streptococcus zooepidemicus as well as on the production and average molecular weight (MW) of hyaluronic acid (HA). The ions were investigated in terms of individual absence from the totally supplemented medium (C+) or individual presence in the non-supplemented medium (C−), where C+ and C− were used as controls. Differences between the effects were analyzed using the Tukey's test at p < 0.05. The adopted criteria considered required the ions, whose individual absence attained at 80% or less of the C+ and their individual presence was 20% or more than the C−. The supplementation was either inhibitory or acted in synergy with other ions, when the individual absence or presence was 20% higher than C+ or 20% lower than C−, respectively. Results showed that the effects of C+ or C− were equal for both the production of HA and its yield from glucose. However, C+ showed to be beneficial to cell growth while the individual absence of Na⁺ was beneficial to the production of HA. The highest MW of HA (7.4 × 10⁷ Da) was observed in the individual presence of Na⁺ in spite of the lowest HA concentration (0.65 g.L⁻¹). These results suggest that the quality of HA can be modulated through the mineral ion supplementation.     

Structural analysis of poly(amidoamine) dendrimer immobilized in crosslinked poly(ethylene glycol)

Polymeric membranes comprised of poly(amidoamine) (PAMAM) dendrimer immobilized in a poly(ethylene glycol) (PEG) network exhibit an excellent CO₂ separation selectivity over H₂. The CO₂ permeability increases with PAMAM dendrimer concentration in the polymeric membrane and becomes 500 times greater than H₂ permeability when the dendrimer content was 50 wt % at ambient conditions (5 kPa of CO₂ partial pressure). However, the detailed morphology of the membrane has not been discussed. The immiscibility of PAMAM dendrimer and PEG matrix results in phase separation, which takes place in a couple of microns scale. Especially, laser scanning confocal microscope captures a 3D morphology of the polymeric blend. The obtained 3D reconstructions demonstrate a bicontinuous structure of PAMAM dendrimer‐rich and PEG‐rich phases, which indicates the presence of PAMAM dendrimer channel penetrating the polymeric membrane, and CO₂ will preferentially pass through the dendrimer channel. In addition, Fourier transform of the 3D reconstructions indicates the presence of a periodic structure. An average size of the dendrimer domain calculated is 2–4 μm in proportion to PAMAM dendrimer concentration. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Synthesis and Mechanical Properties of Polypropylene-based Polymer Hybrids via Controlled Radical Polymerization

Isotactic polypropylene-based graft copolymers linking poly(methyl methacrylate), poly(n-butyl acrylate) and polystyrene were successfully synthesized by a controlled radical polymerization with isotactic polypropylene (iPP) macroinitiator. The hydroxylated iPP, prepared by propylene/10-undecen-1-ol copolymerization with a metallocene/methyl-aluminoxane/triisobutylaluminum catalyst system, was treated with 2-bromoisobutyryl bromide to produce a Br-group containing iPP (PP-g-Br). The resulting PP-g-Br could initiate controlled radical polymerization of methyl methacrylate, n-butyl acrylate and styrene by using a copper catalyst system, leading to a variety of iPP-based graft copolymers with a different content of the corresponding polar segment. These graft copolymers demonstrated unique mechanical properties dependent upon the kind and content of the grafted polar segment.