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Polyhydroxybutyrate (PHB) is a biodegradable biopolymer which is useful for various applications including packing, medical and coating materials. An endospore-forming bacterium (strain BP17) was isolated from composted soil and evaluated for PHB production. Strain BP17, taxonomically identified as Bacillus drentensis, showed enhanced PHB accumulation and was selected for further studies. To achieve maximum PHB production, the culture conditions for B. drentensis BP17 were optimized through response surface methodology (RSM) employing central composite rotatable design (CCRD). The final optimum fermentation conditions included: pineapple peel solution, 11.5% (v/v); tryptic soy broth (TSB), 60 g/ L; pH, 6.0; inoculum size, 10% (v/v) and temperature, 28˚C for 36 h. This optimization yielded 5.55 g/L of PHB compared to the non-optimized condition (0.17 g/L). PHB accumulated by B. drentensis BP17 had a polydispersity value of 1.59 and an average molecular weight of 1.15x10 5 Da. Thermal analyses revealed that PHB existed as a thermally stable semi-crystalline polymer, exhibiting a thermal degradation temperature of 228˚C, a melting temperature of 172˚C and an apparent melting enthalpy of fusion of 83.69 J/g. It is evident that B. drentensis strain BP17 is a promising bacterium candidate for PHB production using agricultural waste, such as pineapple peel as a low-cost alternative carbon source for PHB production.

A simple, surfactant-free solvothermal method is reported for the preparation of <10 nm shape-controlled platinum crystallites. Reactions were carried out in N,Ndimethyformamide (DMF) and DMF−water mixtures. Effects of reaction time and temperature, DMF−water ratio, and metal precursor salt were examined. When the reaction conditions were tuned, ensembles of Pt particles with dominant truncated octahedral/ cuboctahedral or cubic shapes could be formed from the metal acetylacetonate (acac) precursor salt. Metal nanocrystal development was monitored through the use of highresolution transmission electron microscopy (HR-TEM) and X-ray and electrochemical analysis methods. Voltammograms probing CO and formic acid oxidation over shapecontrolled nanocrystals adsorbed to a glassy carbon electrode displayed expected features characteristic of extended ( 111) and (100) facets, confirming the stability and surface cleanliness of particles taken directly from the reaction mixture. A mechanism for Pt reduction and the growth and stabilization of preferentially shaped Pt nanocrystals in the DMF−water solvent system is proposed. The involvement of DMF as a reducing agent and carboxylate ions as weakly coordinating, and hence easily displaced, nanoparticle capping ligands is discussed.

We investigated the morphology, topology, and mechanical characteristics of a loosely cross-linked epoxy network as a function of the varying content of catechol moieties capable of forming reversible, ionic iron− catecholate cross-links. The primary epoxy network structure was kept fixed by a constant mole ratio of difunctional poly(ethylene glycol), monofunctional diluent, and diamine cross-linking agent in all samples. We then systematically replaced the catechol monoepoxide diluent by methyl glycidyl ether, which is incapable of participating in ionic complex formation. This allows the effects of the catechol content on network properties to be isolated and analyzed. Our results support a model in which increasing the concentration of catechol moieties promotes the formation of closely spaced iron− catecholate complex sites. This enables cooperative interactions between netpoints and produces a dramatic improvement in tensile properties. Such ionic interactions are thus a promising approach to creating stiff, strong, and tough load-bearing polymer networks.

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