Production of furfural and cellulose from barley straw using acidified zinc chloride

An effective fractionation process was sought to produce furfural and cellulose-rich solid from barley straw. Acidified zinc chloride (ZnCl₂) was used as a catalyst in order to achieve hemicellulose recovery in the form of liquid hydrolysate. This fractionation process recovered 55.6% of XM (xylan and mannan) in the untreated barley straw under best reaction conditions (10% acidified ZnCl₂, 150 °C, 30 min, and 1/15 of S/L ratio). Hemicellulose hydrolysate was converted into furfural using hydrothermal reaction without additional catalyst. The furfural conversion yield at various reaction temperatures (150, 180, and 210 °C) was in the range of 59.9–64.5%. The two parameters that affected performance in fractionation processing were reaction temperature and time. Reaction severity (Log R0) was used to evaluate the effects of two processing parameters on hemicellulose recovery. In the ZnCl₂ treatment, the data indicated that the proper range of severity was 2.95–3.07 because the XM recovery yield decreased as the reaction condition became more severe beyond that point.     

Precipitation characteristics of paclitaxel in solvent systems with different ion exchange resins

We systematically examined the effect of the solvent system (methanol/water or acetone/pentane) on precipitation characteristics and mechanisms in the increased surface area precipitation (ISAP) with different ion exchange resins for the purification of paclitaxel. When Amberlite IRA 400Cl was added to increase the surface area, the acetone/ pentane system was found to be more effective than the methanol/water system in terms of paclitaxel purity. The addition of surface area-increasing materials increased the yield in the methanol/water system, whereas it decreased the yield in the acetone/pentane system. Precipitates in the methanol/water system were needle-shaped or star-shaped, spreading from the central nucleus along the growing branches, while precipitates in the acetone/pentane system were disk shaped, branching out from around the nucleus. When Amberlite IRA 400Cl was added, it was possible to obtain smaller paclitaxel precipitates in the acetone/pentane system than in the methanol/water system.     

Bioinspired self-adhesive polymer for surface modification to improve antifouling property

The catechol functional group of dopamine (3,4-dihydroxyphenethylamine) forms a strong coordinate bond with both inorganic and organic substrates in a wet environment. The nonfouling surfaces required for this process are typically prepared through the immobilization of poly(ethylene glycol), so-called, PEGylation. In this work, polyaspartamides containing adhesive catechol and methoxy PEG pendants were synthesized from polysuccinimide through successive aminolysis reactions. The adhesion and crosslinking of the polyaspartamide derivatives in pH-controlled aqueous media was successfully utilized to modify a glass surface using a simple immersion method. Contact angle, α-step profiler, SEM and EDS, XPS, and AFM were used to characterize and verify the surface coating. In addition, the biocompatibility and antifouling properties of the modified surface were elucidated with a cell viability test, and a protein adsorption experiment, respectively. This biocompatible polymer system has biomedical application potential for use in adhesives and the surface coating of various biomaterials.     

Preparation of CHF3 plasma polymeric composite membrane and characteristics of surface modification

Low temperature rf-plasma was used to create a plasma-treated polymeric composite membrane made from CHF₃, a material that is very thermally and chemically stable. The chemical and physical properties of the CHF₃ plasma polymers were variously changed by plasma treatment on membrane surface. CHF₃ plasma polymers were efficiently deposited on an aluminum oxide substrate with a pore size of 0.02 μm at the plasma polymerization time 60 min, the rf-power 160W, and the flow rate of the CHF₃ 16 sccm. It was found that O₂ plasma treatment had a much greater effect on the surface roughness of the CHF₃ plasma polymers than did Ar or N₂ plasma treatment. The attachment of functional groups to the CHF₃ plasma polymer surface as a result of plasma treatment increased the intensity of the oxygen functional group peak. It also increased the oxygen content and the O/C ratio. The plasma treatment also made to the surface that became to hydrophilic. The most effective hydrophilic surface modification occurred when the composite parameter ranged from 300-450 kJ·s/kg. It was confirmed that the gas permeability and selectivity changed as a result of crosslinking, chemical etching, and the importing of functional groups to the CHF₃ plasma polymeric membrane.     

NH3 selective catalytic reduction (SCR) of nitrogen oxides (NO x ) over activated sewage sludge char

The de-NO _x performance of sewage sludge chars activated physically using water vapor or chemically using KOH was evaluated. Characteristics of chars activated under different activation temperatures, water vapor concentrations, and KOH/char ratios were analyzed by N₂ adsorption-desorption and FT-IR. Chemically activated chars were more efficient in removing NO _x due to their higher surface area, oxygen functional group and NH₃ adsorption than physically activated chars. The de-NO _x performance of the activated chars is influenced more by chemical properties such as oxygen functional groups and NH₃ adsorption sites than by physical properties like specific surface area and pore volume.     

Morphology and electrical properties of polymethylmethacrylate/poly(styrene‐co‐acrylonitrile)/multi‐walled carbon nanotube nanocomposites

Nanocomposites of blends of polymethylmethacrylate (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN) with multi‐walled carbon nanotubes (MWCNTs) were prepared by melt mixing in a twin‐screw extruder. The dispersion state of MWCNTs in the matrix polymers was investigated using transmission electron microscopy. Interestingly enough, in most of the nanocomposites, the MWCNTs were observed to be mainly located at SAN domains, regardless of the SAN compositions in the PMMA/SAN blend and of the processing method. One possible reason for this morphology may be the π–π interactions between MWCNTs and the phenyl ring of SAN. The shift in G‐band peak observed in the Raman spectroscopy may be the indirect evidence proving these interactions. The percolation threshold for electrical conductivity of PMMA/SAN/MWCNT nanocomposites was observed to be around 1.5 wt %. Nanocomposites with PMMA‐rich composition showed higher electrical conductivity than SAN‐rich nanocomposites at a fixed MWCNT loading. The dielectric constant measurement also showed composition‐dependent behavior. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Removal of As(V) from aqueous solutions by waste crab shells

Waste crab shell, which has some functional groups like -NHCO or NO₂ groups, was used as an adsorbent to remove arsenate ions (As (V)). The functional groups in crab shells were confirmed by FT-IR analysis. Waste crab shell had a high uptake capacity of 35.92 mg/g-dry mass for arsenate ion at pH 4, and the regression curve using the Langmuir isotherm equation fit well with the experimental data. The effects of pH, loading of crab shells, and time on uptake capacity of arsenate ions were also investigated. The adsorption capacity of arsenate ions was increased as the pH value was increased because the amount of negative arsenic species increased as the pH value was increased. Waste crab shells could remove arsenate ions of about 45% with 0.5 g of loading amount, and adsorption of arsenate ions was almost completed in 30 min when initial concentration of arsenate ions was 100 and 9.3 mg/L, respectively. Considering recycling of crab shell, it could be an economical and promising adsorbent.     

Effects of the Bradyrhizobium japonicum waaL (rfaL) Gene on Hydrophobicity,Motility, Stress Tolerance,and Symbiotic Relationship with Soybeans

We cloned and sequenced the waaL (rfaL) gene from Bradyrhizobium japonicum, which infects soybean and forms nitrogen-fixing nodules on soybean roots. waaL has been extensively studied in the lipopolysaccharide (LPS) biosynthesis of enteric bacteria, but little is known about its function in (brady)rhizobial LPS architecture. To characterize its role as O-antigen ligase in the LPS biosynthesis pathway, we constructed a waaL knock-out mutant and its complemented strain named JS015 and CS015, respectively. LPS analysis showed that an LPS structure of JS015 is deficient in O-antigen as compared to that of the wild type and complemented strain CS015, suggesting that WaaL ligates the O-antigen to lipid A-core oligosaccharide to form a complete LPS. JS015 also revealed increased cell surface hydrophobicity, but it showed decreased motility in soft agar plates. In addition to the alteration in cell surface properties, disruption of the waaL gene caused increased sensitivity of JS015 to hydrogen peroxide, osmotic pressure, and novobiocin. Specifically, plant tests revealed that JS015 failed to nodulate the host plant soybean, indicating that the rhizobial waaL gene is responsible for the establishment of a symbiotic relationship between soybean and B. japonicum.     

Structural Basis for Carbapenem-Hydrolyzing Mechanisms of Carbapenemases Conferring Antibiotic Resistance

Carbapenems (imipenem, meropenem, biapenem, ertapenem, and doripenem) are β-lactam antimicrobial agents. Because carbapenems have the broadest spectra among all β-lactams and are primarily used to treat infections by multi-resistant Gram-negative bacteria, the emergence and spread of carbapenemases became a major public health concern. Carbapenemases are the most versatile family of β-lactamases that are able to hydrolyze carbapenems and many other β-lactams. According to the dependency of divalent cations for enzyme activation, carbapenemases can be divided into metallo-carbapenemases (zinc-dependent class B) and non-metallo-carbapenemases (zinc-independent classes A, C, and D). Many studies have provided various carbapenemase structures. Here we present a comprehensive and systematic review of three-dimensional structures of carbapenemase-carbapenem complexes as well as those of carbapenemases. We update recent studies in understanding the enzymatic mechanism of each class of carbapenemase, and summarize structural insights about regions and residues that are important in acquiring the carbapenemase activity.     

Selective catalytic reduction of NOx in lean-burn engine exhaust over a Pt/V/MCM-41 catalyst

The activities of Pt supported on various metal-substituted MCM-41 (V-, Ti-, Fe-, Al-, Ga-, La-, Co-, Mo-, Ce-, and Zr-MCM-41) and V-impregnated MCM-41 were investigated for the reduction of NO by C₃H₆. Among these catalysts, Pt supported on V-impregnated MCM-41 showed the best activity. The maximum conversion of NO into N₂+N₂O over this Pt/V/MCM-41 catalyst (Pt=1 wt.%, V=3.8 wt.%) was 73%, and this maximum conversion was sustained over a temperature range of 70 °C from 270 to 340 °C. The high activity of Pt/V/MCM-41 over a broad temperature range resulted from two additional reactions besides the reaction occurring on usual supported Pt, the reaction of NO with surface carbonaceous materials, and the reaction of NO occurring on support V-impregnated MCM-41. The former additional reaction showed an oscillation characteristic, a phenomenon in which the concentrations of parts of reactant and product gases oscillate continuously. At low temperature, some water vapor injected into the reactant gas mixture promoted the reaction occurring on usual supported Pt, whereas at high temperature, it suppressed the additional reaction related to carbonaceous materials. Five-hundred parts per million of SO₂ added to the reactant gas mixture only slightly decreased the NO conversion of Pt/V/MCM-41.