Determination of the stoichiometry and critical oxygen tension in the production culture of bacterial cellulose using saccharified food wastes

The stoichiometry of the entire reaction in a 50 L scaled-up production culture of bacterial cellulose (BC), using saccharified food wastes (SFW), was analyzed in this study. The stoichiometric analysis was carried out using the chemical formula, yield, degrees of reduction of the major components, and the respiratory quotient (RQ). Based on the stoichiometric analysis, the amounts of substrate, oxygen supply and BC production etc., were able to be predicted. In addition, the amount of energy generated in the culture was predicted based on the oxygen consumption via the stoichiometric analysis. The stoichiometry of BC production using SFW in a 50 L large scale reactor will be useful as a standard for mass production of the culture. The stoichiometric analysis can also help the designers of reactors decide on the boiler capacity and oxygen supply for a large scale bioreactor system. The OUR (oxygen uptake rate) of Acetobacter xylinum KJ1 in a 12 hour-age cultivation was 0.21 mg DO/L·min, from which the critical DO concentration was suggested to be maintained above 3.10 ppm to prevent oxygen limitation during the BC production culture. The results indicated that pure oxygen should be supplied during the exponential phase, where DO depletion was observed. An ascertainment experiment, with the addition of pure oxygen into the culture system, showed BC production of 7.37 g/L, which was considerable productivity.     

Effect of Nafion ionomer and catalyst in cathode layers for the direct formic acid fuel cell with complex capacitance analysis on the ionic resistance

Using platinum (Pt) black and carbon-supported Pt (Pt/C) as cathode catalysts, membrane-electrode assemblies (MEAs) were fabricated with various Nafion ionomer content, and their direct formic acid fuel cell (DFAFC) performances were investigated. In MEAs incorporating Pt black catalysts, the current density at 0.6 V was highest at ionomer/catalyst volume ratio of 1.0, which was consistent with the electrochemical active area (EAS) variation measured by cyclic voltammetry. However, the current density measured at 0.3 V, the cell performance increased with Nafion ionomer content, especially at low ionomer loading, indicating that proton transport rate played an important role. The variation in ionic resistance (R_ion) of cathode layers with Nafion ionomer content was experimentally confirmed by using the complex capacitance analysis of impedance data implemented with nitrogen (cathodes)/hydrogen (anodes) atmosphere. For Pt/C, the layer thickness and EAS of cathode were larger than those of MEA cathode using Pt black; and the current densities at 0.6 V were lower than those of Pt black, suggesting that smaller fraction of EAS was utilized.     

Assembly of strands of multiwall carbon nanotubes and gold nanoparticles using alkanedithiols

Multiwall carbon nanotubes and gold nanoparticles (MWCNT–AuNP) were assembled into strands by cross-linking with alkanedithiols. Long MWCNT strands were first shortened to ∼0.25 μm by chemical oxidation followed by ball-milling, and then thiolated by reaction with cysteamine. The thiol groups on the surfaces of the MWCNT strands combined with Au nanoparticles to produce MWCNT–AuNP strands. A simple mixing of these strands with alkanedithiols resulted in an assembly of strands linked by the alkanedithiols which adsorbed onto the surfaces of the AuNPs attached to the MWCNT–AuNP strands. Short MWCNT–AuNP strands connected to one another in a parallel arrangement, whereas long strands assembled in a crossing arrangement. The possibility of using this method to chemically bond MWCNTs to lower the contact resistance of thin CNT films is discussed.     

Molecular composites created by the solution blending of polyaniline and sulfonated poly(ether sulfone)

New conducting thermally stable blends of polyaniline (PANi) with sulfonated poly(ether sulfone) as a matrix were prepared by a solution‐blending method. Camphorsulfonic acid (CSA) was used as a protonic agent for PANi. A sulfonyl group was introduced into the poly(ether sulfone) to enhance the coulomb interaction among the blends. The influence of the sulfonated group in poly(ether sulfone) was monitored with electrical property measurements. Ultraviolet–visible spectra of the blend compositions showed a well‐developed polaron band. The compatibility of the blends, that is, hydrogen bonding and dispersion at the molecular level, was ascertained with X‐ray diffraction and Fourier transform infrared (FTIR) spectroscopy; these supported intermolecular interaction. A smooth and uniform morphology was observed in the blends. The electrical conductivity of the blends increased up to 14 S/cm with the protonation of the PANi complex with CSA, and the percolation threshold was found to be 2 wt % PANi. These new blends showed increases in conductivity and compatibility over other PANi–poly(ether sulfone) blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of high‐molecular‐weight sericin by γ irradiation

We conducted this study to examine the changes in the molecular structure and physiological activities of silk sericin after γ irradiation. Sericin from Bombyx mori was extracted with an Na₂CO₃ solution. The molecular weight distribution of sericin increased in the gel permeation chromatography and sodium dodecyl sulfate/polyacrylamide gel electrophoresis results as the irradiation dose increased. Circular dichroism data also revealed that the α‐helix contents decreased with the irradiation dose. Ultraviolet absorption was shown a different pattern between the irradiated and unirradiated sericin. However, the Fourier transform infrared spectrum was not changed in all of the groups. Furthermore, the irradiated sericin was significantly increased in 2,2‐diphenyl‐1‐picryl‐hydrazil radical scavenging, and the tyrosinase inhibitory activities increased with irradiation dose. Therefore, γ irradiation was an effective method for producing high‐molecular‐weight sericin and for developing functional foods and cosmetics. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Alignment of a nematic liquid crystal on nano‐grooved material

We demonstrate the alignment characteristics of a nematic liquid crystal on the surface of a nanoimprinted material that is a functionally graduated composite suitable for the alignment of a liquid crystal on a groove surface processed by nanoimprinting lithography. With the electro‐optic characteristics shown in twisted nematic and in‐plane switching modes, the potential liquid crystal applications are examined. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of poly(ε‐caprolactone)/clay nanocomposites using polyhedral oligomeric silsesquioxane surfactants as organic modifier and initiator

Poly(ε‐caprolactone)/clay nanocomposites were synthesized by in situ ring‐opening polymerization of ε‐caprolactone in the presence of montmorillonite modified by hydroxyl functionalized, quaternized polyhedral oligomeric silsesquioxane (POSS) surfactants. The octa(3‐chloropropyl) polyhedral oligomeric silsesquioxane was prepared by hydrolytic condensation of 3‐chloropropyltrimethoxysilane, which was subsequently quaternized with 2‐dimethylaminoethanol. Montmorillonite was modified with the quaternized surfactants by cation exchange reaction. Bulk polymerization of ε‐caprolactone was conducted at 110°C using stannous octoate as an initiator/catalyst. Nanocomposites were analyzed by X‐ray diffraction, transmission electron microscopy, thermo gravimetric analysis, and differential scanning calorimetry. Hydroxyl functionalized POSS was employed as a surface modifier for clay which gives stable clay separation for its 3‐D structure and also facilitates the miscibility of polymer with clay in the nanocomposites due to the star architecture. An improvement in the thermal stability of PCL was observed even at 1 wt % of clay loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Estimation of illuminant chromaticity based on highlight detection for face images with varying illumination

Illuminant chromaticity estimation is required in the fields of the tracking and recognition of human faces, compensation and detection of skin color, image reproduction, and color constancy. This article proposes a simple and effective method to estimate the illuminant chromaticity using highlights from the face region. We first select the candidate points through the detection of highlights around the leftmost pixel of the rg chromaticity space from the facial images under various illuminant conditions and then estimate the illuminant chromaticity by averaging the chromaticities of the candidate points. To enhance the illuminant chromaticity estimation accuracy, we propose a more elaborate estimation method, which effectively readjusts the candidate points of the highlight regions according to the conditions derived from two ethnic and three illuminant groups. The experiment results show that our proposed method reliably estimates the illuminant chromaticity under various color temperatures and illuminant directions. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 188–199, 2014     

Preparation and properties of acrylonitrile–butadiene rubber–graphene nanocomposites

The graphene oxide (GO) was prepared by sonication‐induced exfoliation from graphite oxide, which was produced by oxidation from graphite flakes with a modified Hummer's method. The GO was then treated by hydrazine to obtain reduced graphene oxide (rGO). On the basis of the characterization results, the GO was successfully reduced to rGO. Acrylonitrile–butadiene rubber (NBR)–GO and NBR–rGO composites were prepared via a solution‐mixing method, and their various physical properties were investigated. The NBR–rGO nanocomposite demonstrated a higher curing efficiency and a change in torque compared to the gum and NBR–GO compounds. This agreed well with the crosslinking density measured by swelling. The results manifested in the high hardness (Shore A) and high tensile modulus of the NBR–rGO compounds. For instance, the tensile modulus at a 0.1‐phr rGO loading greatly increased above 83, 114, and 116% at strain levels of 50, 100, and 200%, respectively, compared to the 0.1‐phr GO loaded sample. The observed enhancement was highly attributed to a homogeneous dispersion of rGO within the NBR matrix; this was confirmed by scanning electron microscopy and transmission electron microscopy analysis. However, in view of the high ultimate tensile strength, the NBR–GO compounds exhibited an advantage; this was presumably due to strong hydrogen bonding or polar–polar interactions between the NBR and GO sheets. This interfacial interaction between GO and NBR was supported by the marginal increase in the glass‐transition temperatures of the NBR compounds containing fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42457.     

Proteomic Insights into Sulfur Metabolism in the Hydrogen-Producing Hyperthermophilic Archaeon Thermococcus onnurineus NA1

The hyperthermophilic archaeon Thermococcus onnurineus NA1 has been shown to produce H₂ when using CO, formate, or starch as a growth substrate. This strain can also utilize elemental sulfur as a terminal electron acceptor for heterotrophic growth. To gain insight into sulfur metabolism, the proteome of T. onnurineus NA1 cells grown under sulfur culture conditions was quantified and compared with those grown under H₂-evolving substrate culture conditions. Using label-free nano-UPLC-MS^E-based comparative proteomic analysis, approximately 38.4% of the total identified proteome (589 proteins) was found to be significantly up-regulated (≥1.5-fold) under sulfur culture conditions. Many of these proteins were functionally associated with carbon fixation, Fe–S cluster biogenesis, ATP synthesis, sulfur reduction, protein glycosylation, protein translocation, and formate oxidation. Based on the abundances of the identified proteins in this and other genomic studies, the pathways associated with reductive sulfur metabolism, H₂-metabolism, and oxidative stress defense were proposed. The results also revealed markedly lower expression levels of enzymes involved in the sulfur assimilation pathway, as well as cysteine desulfurase, under sulfur culture condition. The present results provide the first global atlas of proteome changes triggered by sulfur, and may facilitate an understanding of how hyperthermophilic archaea adapt to sulfur-rich, extreme environments.