Evaluation and Optimization of Organic Acid Pretreatment of Cotton Gin Waste for Enzymatic Hydrolysis and Bioethanol Production

This paper investigates the efficiency of the organic acids on the pretreatment of an industrially generated cotton gin waste for the removal of lignin, thereby releasing cellulose and hemicellulose as fermentable sugar components. Cotton gin waste was pretreated with various organic acids namely lactic acid, oxalic acid, citric acid, and maleic acid. Among these, maleic acid was found to be the most efficient producing maximum xylose sugar (126.05?±?0.74 g/g) at the optimum pretreatment condition of 150 °C, 500 mM, and 45 min. The pretreatment efficiency was comparable to the conventional dilute sulfuric acid pretreatment. A lignin removal of 88% was achieved by treating maleic acid pretreated biomass in a mixture of sodium sulfite and sodium chlorite. The pretreated biomass was further evaluated for the release of sugar by enzymatic hydrolysis and subsequently bioethanol production from hydrolysates. The maximum 686.13 g/g saccharification yield was achieved with maleic acid pretreated biomass which was slightly higher than the sulfuric acid (675.26 g/g) pretreated waste. The fermentation of mixed hydrolysates(41.75 g/l) produced 18.74 g/l bioethanol concentration with 2.25 g/l/h ethanol productivity and 0.48 g/g ethanol yield using sequential use of Saccharomyces cerevisiae and Pichia stipitis yeast strains. The production of bioethanol was higher than the ethanol produced using co-culture in comparison to sequential culture. Thus, it has been demonstrated that the maleic acid pretreatment and fermentation using sequential use of yeast strains are efficient for bioethanol production from cotton gin waste.     

Remote control of the reversible assembly/disassembly of supramolecular aggregates

ABSTRACT

A multi-component system is presented in which the actuation of a copper-loaded nanoswitch by zinc(II) ions as an external trigger and the thereby prompted release of copper(I) ions allows self-assembly of 11 parts resulting in the formation of a three-component supramolecular prism. Using the same protocol, a three-component rectangle was made from eight parts. Disassembly of the aggregates was accomplished by selective removal of zinc(II) ions using hexacyclen. In sum, the reversible assembly and disassembly of supramolecular aggregates was controlled in a multi-component mixture through intermolecular communication using a second messenger.     

Folate-decorated succinylchitosan nanoparticles conjugated with doxorubicin for targeted drug delivery

Amphiphilic biodegradable succinylchitosan nanoparticles modified with folic acid are described that act as an emulsifier to form nanoparticles. Their molecular structures and physicochemical as well as self‐assembly properties are characterized by means of FT‐IR, ¹H NMR, FESEM, DLS, and TEM. The nanoparticles are 60–80 nm in size and are not toxic in vitro. They are immobilized with the cytostatic drug doxorubicin. Specific transport of doxorubicin by the nanoparticles into the folate‐receptor‐overexpressing cancer cells and its biological activity as well as in vitro release are demonstrated. It is shown that under acidic condition more drug is released. The nanoparticles can thus not only specifically deliver doxorubicin to its target, but also release the drug depending on the pH.

     

Screening and rank ordering of reversible mechanism‐based inhibitors of Hepatitis C virus NS3 protease using electrospray ionization mass spectrometry

An affinity‐selection study using size exclusion chromatography (SEC) combined with off‐line electrospray ionization mass spectrometry (ESI‐MS) was performed on libraries of peptidic α‐ketoamide inhibitors directed against the hepatitis C virus (HCV) NS3 protease. A limiting amount of HCV NS3 protease (25 µM ) was incubated with equimolar amounts (100 µM ) of 49 reversible mechanism‐based ketoamide inhibitors, previously grouped into seven sets to ensure clearly distinguishable mass differences of the enzyme‐inhibitor complexes (>10 Da). The unbound compounds were separated rapidly from the protease and the protease‐inhibitor complexes by SEC spin columns. The eluate of the SEC was immediately analyzed by direct‐infusion ESI‐MS. An enzyme‐inhibitor complex, with a molecular mass corresponding to the NS3 protease binding to the preferred inhibitor, SCH212986, was the only molecular species detected. By increasing the molar ratio of HCV NS3 protease to inhibitors to 1:2 while keeping the inhibitors' concentration constant, the complex of the second most tightly bound inhibitor, SCH215426, was also identified. Although the potencies of these inhibitors were virtually un‐measurable by kinetic assays, a rank order of CVS4441 > SCH212986 > SCH215426 was deduced for their inhibition potencies by direct competition experiment with CVS4441 ( M ). As discussed in the article, through judicious application of this strategy, even large libraries of fairly weak, reversible and slow‐binding inhibitors could be rapidly screened and rank ordered to provide critical initial structure‐activity insights. Copyright © 2011 John Wiley & Sons, Ltd.     

Fabrication of multi-structure nanocarbons from carbon xerogel: a unique scaffold towards bio-imaging

A novel route has been developed to fabricate different carbon nanostructures having individual morphology of carbon nanoparticles: nanofullerene, nanocube, nanoleaf and porous nanorods, through the combustion of carbon xerogel with nitric acid. These fabricated nanostructures exhibited bright green fluorescence under the exposure of UV light.     

Self-assembling properties of lactic acid derivative with several ester linkages in the molecular core

The effect of several polar ester linkage groups incorporated in the molecular core of a chiral lactic acid derivative on self-assembling properties has been investigated by polarizing optical microscopy, small angle X-ray diffraction, differential scanning calorimetry, optical and electro--optical studies. The compound possesses the paraelectric smectic A* (SmA*) and ferroelectric smectic C* (SmC*) phases over a broad temperature range. Mesomorphic behaviour, spontaneous polarization, birefringence, optical transmission, dielectric anisotropy and structural properties of the self-assembled chiral material have been determined. The obtained results are discussed and compared with that of other liquid crystalline materials. Experimentally determined spontaneous polarization and tilt angle values are also used to elucidate the nature of SmC* to SmA* phase transition. The effect of polar ester linkages in the molecular core has also been discussed.     

A Systematic Study of Fluorescence‐Based Detection of Nitroexplosives and Other Aromatics in the Vapor Phase by Microporous Metal–Organic Frameworks

A systematic study is conducted on four microporous metal–organic framework compounds built on similar ligands but different structures, namely [Zn₃(bpdc)₃(bpy)] ? 4 DMF ? H₂O ( 1 ), [Zn₃(bpdc)₃(2,2′dmbpy)] ? 4 DMF ? H₂O ( 2 ), [Zn₂(bpdc)₂(bpe)] ? 2 DMF ( 3 ), and [Zn(bpdc)(bpe)] ? DMF ( 4 ) (bpdc=4,4′‐biphenyldicarboxylate; bpy=4,4′‐bipyridine; 2,2′dmbpy=2,2′‐dimethyl‐4,4′bipyridine; bpe=1,2‐bis(4‐pyridyl)ethane; DMF=N,N′‐dimethylformamide) to investigate their photoluminescence properties and sensing/detection behavior upon exposure to vapors of various aromatic molecules (analytes) including nitroaromatic explosives. The results show that all four compounds are capable of detecting these molecules in the vapor phase through fluorescence quenching or enhancement. Both electrochemical measurements and theoretical calculations are performed to analyze the analyte–MOF interactions, to explain the difference in signal response by different analytes, and to understand the mechanism of fluorescence quenching or enhancement observed in these systems. Interestingly, compound 3 also shows an emission frequency shift when exposed to benzene (BZ), chlorobenzene (ClBZ), and toluene (TO), which provides an additional variable for the identification of different analytes in the same category.     

Cu<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ni<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> alloy nanoparticles embedded SiO<Subscript>2</Subscript> films: synthesis and structure

Cu–Ni fcc alloy nanoparticles (NPs) of tunable atomic ratios were generated in SiO₂ films. The films were prepared using the Cu(NO₃)₂ and Ni(NO₃)₂ co-doped inorganic–organic hybrid silica sols by single dipping. Transparent, crack-free, glassy SiO₂ films of 310 ± 10 nm in thickness embedded with high mol percent of Cu–Ni alloy NPs were yielded after annealing at 750 °C in 10% H₂-90% Ar atmosphere. Nominal compositions of the films were 20 mol% (Cu–Ni)-80 mol% SiO₂. Optical spectral study of the heat-treated films showed disappearance of Cu plasmon bands due to Cu–Ni alloy formation. Grazing incidence X-ray diffraction (GIXRD) studies revealed the formation of Cu–Ni alloy (2:1, 1:1 and 1:2) NPs inside the SiO₂ film. GIXRD showed a systematic shifting of the diffraction peaks with respect to the fcc Cu–Ni alloy composition, maintaining the nominal ratios. Transmission electron microscopy (TEM) studies of the representative Cu_0.5Ni_0.5-doped film showed existence of homogeneously dispersed Cu–Ni alloy NPs of average size 6.35 nm inside the SiO₂ matrix. The energy dispersive X-ray scattering (EDX) analysis of the individual NPs using the nano-probe (scanning TEM mode) confirmed the presence of both the Cu and Ni with the desired atomic ratio.     

Sonochemical synthesis and application of rhodium–graphene nanocomposite

Abstract  

Highly water dispersible rhodium–graphene nanocomposite have been successfully synthesized by the simple reduction of Rh³⁺ salt on poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEO/PPO/PEO) triblock copolymer or pluronic-stabilized graphene oxide (GO) nanosheets with borohydride. Rhodium nanoparticles, having average size of 1–3 nm, are homogeneously distributed through out the graphene sheets. Some porous structures of graphene sheets have also been observed after the reduction of pluronic-stabilized GO in the presence of metal ions. The material is very effective for hydrogenation of arenes, especially for benzene as the substrate material at the room temperature and 5 atm pressure of hydrogen.