Enhanced Enzymatic Synthesis of a Cephalosporin,Cefadroclor, in the Presence of Organic Co-solvents

In this study, we investigated the enzymatic synthesis of a semi-synthetic cephalosporin, cefadroclor, from 7-aminodesacetoxymethyl-3-chlorocephalosporanic acid (7-ACCA) and p-OH-phenylglycine methyl ester (D-HPGM) using immobilized penicillin G acylase (IPA) in organic co-solvents. Ethylene glycol (EG) was employed as a component of the reaction mixture to improve the yield of cefadroclor. EG was found to increase the yield of cefadroclor by 15–45%. An investigation of altered reaction parameters including type and concentration of organic solvents, pH of reaction media, reaction temperature, molar ratio of substrates, enzyme loading, and IPA recycling was carried out in the buffer mixture. The best result was a 76.5% conversion of 7-ACCA, which was obtained from the reaction containing 20% EG (v/v), D-HPGM to 7-ACCA molar ratio of 4:1 and pH 6.2, catalyzed by 16 IU mL^?1 IPA at 20 °C for 10 h. Under the optimum conditions, no significant loss of IPA activity was found after seven repeated reaction cycles. In addition, cefadroclor exhibited strong inhibitory activity against yeast, Bacillus subtilis NX-2, and Escherichia coli and weaker activity against Staphylococcus aureus and Pseudomonas aeruginosa. Cefadroclor is a potential antibiotic with activity against common pathogenic microorganisms.     

Potential of Mangrove-Associated Endophytic Fungi for Production of Carbohydrolases with High Saccharification Efficiency

The endophytic fungi represent a potential source of microorganisms for enzyme production. However, there have been only few studies exploiting their potential for the production of enzymes of industrial interest, such as the (hemi)cellulolytic enzymatic cocktail required in the hydrolysis of lignocellulosic biomass. Here, a collection of endophytic fungi isolated from mangrove tropical forests was evaluated for the production of carbohydrolases and performance on the hydrolysis of cellulose. For that, 41 endophytic strains were initially screened using a plate assay containing crystalline cellulose as the sole carbon source and the selected strains were cultivated under solid-state fermentation for endoglucanase, β-glucosidase, and xylanase enzyme quantification. The hydrolysis of a cellulosic material with the enzymes from endophytic strains of the Aspergillus genus resulted in glucose and conversion values more than twofold higher than the reference strains (Aspergillus niger F12 and Trichoderma reesei Rut-C30). Particularly, the enzymes from strains A. niger 56 (3) and A. awamori 82 (4) showed a distinguished saccharification performance, reaching cellulose conversion values of about 35% after 24 h. Linking hydrolysis performance to the screening steps played an important role towards finding potential fungal strains for producing enzymatic cocktails with high saccharification efficiency. These results indicate the potential of mangrove-associated endophytic fungi for production of carbohydrolases with efficient performance in the hydrolysis of biomass, thus contributing to the implementation of future biorefineries.     

Density,Viscosity, and Glass Transition of an Ethylenediamine–Ethylene Glycol Binary System

Densities ρ and viscosities η were measured for the binary mixtures of ethylenediamine (EDA) and ethylene glycol (EG) in the temperature range 288.15–323.15 K for ρ and at 273.15–323.15 K for η, both of which are broader temperature ranges than those reported previously. The value of ρ monotonously decreases against the mole fraction of EDA, x _EDA, and increasing temperature. The concentration dependence of η exhibits a maximum in the intermediate concentration range at all temperatures measured. The glass transition temperature, T _g, for samples with x _EDA < 0.7 was measured using differential scanning calorimetry. The measured T _g values show a peak in the intermediate concentration range, which is a behavior similar to that of η; however, the peak concentrations for η and T _g did not precisely align because of a deviation in the maximum hydrogen-bond density. The partial molar volumes for EDA and EG and the thermal expansivities, α, were obtained from ρ. Results in the present study are discussed in terms of the extensively increasing hydrogen-bond density for polyamine–polyhydric alcohol systems.     

Solutions of mixtures of cellulose and synthetic polymers in <Emphasis Type="Italic">N</Emphasis>-methylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide

Phase state and morphological features of solutions of cellulose blends with rigid-chain thermotropic LC copolyesters and isotropic poly(m-phenyleneisophthalamide) in the highly polar donor solvent N-methylmorpholine-N-oxide are studied by DSC and polarization microscopy. The ternary phase diagram for the cellulose-copolyesters-N-methylmorpholine-N-oxide system is constructed. Rheological characteristics of the prepared solutions are studied using capillary and rotary rheometers under the regimes of continuous and periodic shear deformation. Rheological characteristics of cellulose solutions with copolyesters in N-methylmorpholine-N-oxide with their different phase states are shown to change in accordance with the traditional mechanism of flow for solutions with high specific interactions between their components. However, the character of the rheological behavior of mixtures of cellulose with poly(m-phenyleneisophthalamide) in N-methylmorpholine-N-oxide primarily stems from structural-morphological transformations in solutions taking place upon deformation.     

Bioconversion of cellulose and simultaneous production of thermoactive exo- and endoglucanases by <Emphasis Type="Italic">Fusarium oxysporum</Emphasis>

Saccharification of cellulose is a promising method for production of biofuels. However, low bioconversion efficiency of cellulose to soluble sugars is a major challenge. In this study, a cellulolytic strain of Fusarium oxysporum was cultivated on pure cellulosic substrates (avicel, α-cellulose, carboxymethylcellulose and methylcellulose) and conversion efficiency into glucose was investigated. Production of exo- and endoglucanases during the bioconversion process was evaluated. Influence of pH on saccharification of cellulose and enzyme production by F. oxysporum were determined. Highest yield of glucose (1.76 μmol/ml) was obtained from F. oxysporum on methyl cellulose at 192 h under basal conditions. Liberated glucose under optimized condition of pH 6.0 at 96 h of fermentation was 2.12 μmol/ml with maximum production of exo- and endoglucanases (23.70 and 34.72 U/mg protein, respectively). The crude exo- and endoglucanases had optimum activities at pH 8.0, 70 °C and pH 7.0, 50 °C, respectively. The enzymes were stable over pH of 4.0–7.0 with relative residual activity above 60% after 1 h incubation. Exoglucanase activity was enhanced by Ca²⁺ and Cu²⁺ at 5 mM and Mg²⁺ at 10 mM. Endoglucanase activity was greatly enhanced in the presence of Mn²⁺, Ca²⁺, Mg²⁺, Cu²⁺ and Fe³⁺ at 5 and 10 mM. Activities of both enzymes were inhibited in the presence of Hg²⁺ at 5 and 10 mM. Results show that F. oxysporum possessed good cellulolytic enzyme system for efficient conversion of cellulose. Exhibited thermotolerance of exoglucanase with the striking tolerance of endoglucanase to metal ions demonstrate potentials of enzymes for biofuel industry.     

Extensional rheology of cellulose/NaOH/urea/H<Subscript>2</Subscript>O solutions

The extensional flow behaviors of cellulose/NaOH/urea/H₂O solution were investigated by using capillary breakup extensional rheometry (CaBER). The effects of temperature, storage time and cellulose concentrations on both the storage modulus G′ and the loss modulus G″ were also analyzed. For 2 wt% cellulose solution, the G′, G″ and filament lifetime remained unchanged after long storage time. While, for 4 wt% cellulose solution, physical gels could form at either higher temperature or for longer storage time, and the filament lifetime, the relaxation time (λ _e ) and the initial extensional viscosity (η _e0) first increased and then decreased with increase of the storage time. The transition points of the filament lifetime shifted to lower storage time with the increase of the temperature. The η _e0 is proportional to λ _e . The results presented suggest that the extensional properties of the cellulose/NaOH/urea/H₂O solution first increase and then decrease during the gelation process, and the spinning time, which decreases linearly with the increase in the storage temperature, must be controlled below the time that η _e0 starts to decrease.     

Phase-equilibrium and cellulose-coagulation kinetics for cellulose solutions in <Emphasis Type="Italic">N</Emphasis>-methylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide

The dissolution of cellulose in N-methylmorpholine-N-oxide monohydrate and the dissolution of N-methylmorpholine-N-oxide monohydrate in water have been studied via optical interferometry. A part of the phase diagram for the cellulose/N-methylmorpholine-N-oxide system has been constructed. The phase diagram is characterized by crystalline equilibrium, hysteresis of the melting temperatures of the solvents, and a region of anisotropy. Optical interferometry has been used for the first time to study the kinetics of cellulose coagulation during the interaction of cellulose solutions in N-methylmorpholine-N-oxide with water and water solutions of N-methylmorpholine-N-oxide. Information on the values of interdiffusion coefficients and the morphologies of the resulting cellulose films has been obtained. The possibility to use optical interferometry to analyze the interaction of a solution with the coagulating agent in the case of cellulose fiber and film formation has been demonstrated. The influences of temperature, the nature of the coagulating agent, and the cellulose content on the kinetics of the process and morphologies of the formed films have been shown. The use of N-methylmorpholine-N-oxide as a part of the coagulation system decreases the rate of interdiffusion of solutions, thereby resulting in a more uniform and dense morphology of cellulose films. Increased temperature causes diffusion acceleration, thereby leading to the formation of an anisotropic morphology of the cellulose films.     

A Thermodynamic and Physical Study on (1-Hexyl-3-methylimidazolium Chloride + 1-Pentanol and Ethylene Glycol) Binary Mixtures at Temperatures (293.15–333.15) K

Densities, ρ, viscosities, η, and refractive indices, n _D, for 1-hexyl-3-methyl imidazolium chloride ([hmim]Cl) (IL), 1-pentanol, and ethylene glycol (EG), and for the binary mixtures {x ₁[hmim]Cl + x ₂1-pentanol} and {x ₁[hmim]Cl + x ₂EG} were measured over the entire composition range at temperatures (293.15–333.15) K and ambient pressure. The excess molar volumes, \( V_{\text{m}}^{\text{E}} \), and viscosity deviations, Δη, for the binary mixtures were calculated from the experimental data. The \( V_{\text{m}}^{\text{E}} \) values of {x ₁[hmim]Cl + x ₂1-pentanol} mixtures are negative over the entire composition range at all temperatures, and increase with increasing temperature in the alcohol rich region and decrease with increasing temperature in the IL rich range. The \( V_{\text{m}}^{\text{E}} \) values of {x ₁[hmim]Cl + x ₂EG} mixture are positive in the alcohol rich range and negative in the IL rich range at all temperatures, and decrease with increasing temperature. Viscosity deviations of both mixtures are negative over the entire composition range at all temperatures and decrease with increasing temperature. The excess molar properties were correlated by Redlich–Kister equation, and the excess molar volumes were correlated using the PFP model. The fitting parameters and standard deviations were determined.     

Atmospheric levels and distribution of Dechlorane Plus in an E-waste dismantling region of East China

Atmospheric concentrations of Dechlorane Plus(DP)were investigated in Taizhou,an electronic-waste(E-waste)dismantling region in East China.Passive air samplers with polyurethane foam(PUF)disks were deployed every three months during the sampling period of September 2009-August 2010.The total DP(syn-and anti-DP)concentrations in air ranged from not detected to 277 pg/m~3,with a mean concentration of 53.9 pg/m~3.A generally declining trend of DP levels was found from the E-waste dismantling region to the peripheral areas.The median values of total DP concentrations in autumn,winter,spring and summer were 52.2,28.8,39.7 and 30.1 pg/m~3,respectively.The seasonal variations of DP concentrations were mainly associated with the intensity of E-waste dismantling activities and meteorological conditions.The mean value of anti-DP fractional abundance(f_(anti))was 0.74±0.08,which was consistent with those in the commercial DP products.This study confirmed a significant emission source related to the distribution of atmospheric DP in the E-waste dismantling area and supplied information for the seasonal variation of DP in the atmosphere.     

Switching diastereoselectivity of direct Mannich-type reaction of cyclic ketones by polymeric laponite nanoclay catalyst

A new polymeric laponite nanoclay heterogeneous catalytic system based on HPMC (hydroxypropyl methyl cellulose) was developed for direct Mannich-type reaction of ketones with substituted benzaldehydes and anilines to afford corresponding β-amino ketones in good to high yields. Interestingly, cyclic ketones exhibited different chemoselectivity. Cyclopentanone underwent aldol condensation to give crossed-aldol product, while cyclohexanone and cyclopentanone afforded corresponding Mannich adducts. In the case of cyclohexanone, stereoselectivity was changed depending on the nature of the substitution on benzaldehydes, in which, moderate electron-donating and electron-withdrawing groups afforded the anti isomer as major products, but strongly electron-donating substituted benzaldehydes led to syn isomer as the major Mannich adducts. Mannich reaction with cycloheptanone led to Mannich adducts with excellent syn selectivity.     

The impact of antibiotics on bacterial cellulose in vivo

This study investigated how antibiotics, to which Gluconacetobacter hansenii is naturally resistant, impact cellulose crystallinity, allomorph, aggregation into bundles and layers, cellulose yield, and cell morphology. G. hansenii was exposed to 100 μg/mL ampicillin, chloramphenicol, and kanamycin for 7 days, and cellulose structure was analyzed using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Biomass and cellulose weights were also assessed. Ampicillin increased bundle thickness, and the bundles also showed nodular deposits indicative of non-cellulosic exopolysaccharide deposition. Ampicillin also yielded the lowest amount of cellulose per gram of biomass (p < 0.01) and induced significant filamentation behavior. Chloramphenicol inhibited biomass production (p < 0.01), increased the I-α allomorph content (p < 0.01), and also induced filamentation, though not as profusely as ampicillin. We hypothesize that defects in the peptidoglycan layer and in protein production lowered cellulose yield and promoted cells to undergo filamentation as a survival tactic. Additionally, we hypothesize that antibiotic stress caused additional exopolysaccharides to be produced and that they likely enhanced glucan chain aggregation into higher-order structures. Our findings have significant implications for downstream applications such as genetically engineering G. hansenii to produce bacterial cellulose with modified properties.     

Effect of Evolutionary Adaption on Xylosidase Activity in Thermotolerant Yeast Isolates <Emphasis Type="Italic">Kluyveromyces marxianus</Emphasis> NIRE-K1 and NIRE-K3

Efficient use of xylose along with glucose is necessary for the economic production of lignocellulosic based biofuels. Xylose transporters play an important role in the microorganisms for efficient utilization of xylose. In the present study, a novel method has been developed for a rapid assay of xylose transport activity in the xylose-utilizing isolates and other known yeasts. An assay was conducted to compare the activity of β-xylosidase using p-nitrophenyl-β-d-xylopyranoside (pNPX) in the intact, intracellular, and extracellular yeasts cells showing xylose transporter. Saccharomyces cerevisiae (MTCC 170) showed no xylosidase activity, while little growth was observed in the xylose-containing medium. Although other yeasts, i.e., Kluyveromyces marxianus NIRE-K1 (MTCC 5933), K. marxianus NIRE-K3 (MTCC 5934), and Candida tropicalis (MTCC 230), showed xylosidase activity in intact, intracellular, and extracellular culture. The xylosidase activity in intact cell was higher than that of extracellular and intracellular activity in all the yeast cells. The enzyme activity was higher in case of K. marxianus NIRE-K1 and K. marxianus NIRE-K3 rather than the C. tropicalis. Further, better xylosidase activity was observed in adapted K. marxianus cells which were 2.79–28.46 % higher than that of native (non-adapted) strains, which indicates the significant improvement in xylose transportation.     

Properties and <Emphasis Type="Italic">N</Emphasis>-glycosylation of recombinant endoglucanase II from <Emphasis Type="Italic">Penicillium verruculosum</Emphasis>

Cellulases are the main components of enzyme complexes used in biotransformation processes of plant raw materials into valuable commercial products. Endoglucanase II (EG II) from the Penicillium verruculosum fungus was cloned into Penicillium canescens. The homogeneous recombinant EGII form is isolated and its properties are studied in comparison with the native enzyme. The N-glycosylation sites and the structure of the N-linked glycans are been determined using mass spectrometry. The biochemical and catalytic properties, as well as the N-glycosylation type of the obtained recombinant EGII form, appear to be close to the native enzyme. At the two potential N-glycosylation sites (N42 and N194) of both forms of the enzyme, N-linked high mannose glycans (or their enzymatic “trimming” products) according to the general formula (Man)_1–9(GlcNAc)₂ are detected. No glycosylation is found at the third potential site (N19).     

Molecular dynamics simulations of the characteristics of sodium carboxymethyl cellulose with different degrees of substitution in a salt solution

Sodium carboxymethyl cellulose (SCMC) with different degrees of substitution (DS) possesses structural characteristics and physicochemical properties that are important in broad areas of industrial applications. This reported work investigated the structural characteristics, including the effective length (L _ef), the radius of gyration (R _g), and the hydrodynamic radius (R _H), and the physicochemical properties, including intrinsic viscosity ([η]) and salt tolerance, of SCMC with a DS more than 1.0 in NaCl solution using molecular dynamics (MD) simulations. In the MD simulations, the DS of SCMC varied from 1.2 to 2.8, and the NaCl concentration varied from 0 to 1.4 mol/L. MD simulation results showed that with the increment of NaCl concentration, the L _ef (or R _g or R _H) of SCMC decreased; with the increment of the DS, the L _ef of SCMC increased. Also, the variation tendency of [η] in the NaCl solution was consistent with its L _ef (or R _g or R _H). It was noted that the salt tolerance (represented by D) of SCMC increased as the DS increased. In addition, the sharp variation of the D value of SCMC occurred in the range of DS of 1.6 to 2.0, which agreed with the reported experimental results. Radial distribution function analyses showed that the Na⁺ cations had a stronger interaction with the carboxyl groups in SCMC with lower DS when it was present in a salt solution of higher concentration, which also reasonably explained the variation of L _ef, R _g, R _H, [η], and D of SCMC in NaCl solution.     

Biosynthesis of Gold Nanoparticles by Flavonoids from <Emphasis Type="Italic">Lilium casa blanca</Emphasis>

Biosynthesis of gold nanoparticles (GNPs) by flavonoids from Lilium casa blanca has been developed. Several parameters such as pH, reaction temperature, reaction time and concentration of flavonoids were explored to control the formation of the GNPs. The synthesized GNPs were characterized by UV–Vis spectroscopy, transmission electron microscopy and X-ray diffraction. Stability and catalytic activity of the synthesized GNPs were also discussed. The results showed that the synthesized GNPs were in spherical, about 2.6 nm, with a face centered cubic structure. Synthesized GNPs showed good catalytic activity in the reduction of p-nitrophenol (p-NP) to p-aminphenol (p-AP). This method for synthesis of GNPs is simple, economic, nontoxic and efficient.     

Slow Down Dewetting in Polymer Films by Isocyanate-treated Graphite Oxide

Isocyanate-treated graphite oxides(i GOs) were well-dispersed into the polystyrene(PS) thin films and formed a novel network structure. With control in fabrication, an i GOs-web layer was horizontally embedded near the surface of the films and thus formed a composite slightly doped by i GOs. This work demonstrated that the i GOs network can remarkably depress the dewetting process in the polymer matrix of the composite, while dewetting often leads to rupture of polymer films and is considered as a major practical limit in using polymeric materials above their glass transition temperatures(Tg). Via annealing the 50–120 nm thick composite and associated neat PS films at temperatures ranging from 35 °C to 70 °C above Tg, surface morphology evolution of the films was monitored by atomic force microscopy(AFM). The i GOs-doped PS exhibited excellent thermal stability, i.e., the number of dewetting holes was greatly reduced and the long-term hole growth was fairly restricted. In contrast, the neat PS film showed serious surface fluctuation and a final rupture induced by ordinary dewetting. The method developed in this work may pave a road to reinforce thin polymer films and enhance their thermal stability, in order to meet requirements by technological advances.     

Peroxy radicals as motional probes at the end of isolated polystyrene chains and on the cellulose surfaces in vacuum

The isolated polystyrene chains spin-labeled with peroxide radical at the free end (IPSOO) in which the chain roots were covalently bonded to the surface of microcrystalline cellulose (MCC) powder were produced by mechanochemical polymerization of styrene initiated by MCC mechanoradicals. The IPSOO was used as motional probes at the ends of isolated polystyrene chains tethered on the surface of MCC powder. Two modes for the molecular motion of IPSOO were observed. One was a tumbling motion of IPSOO on the MCC surface, defined as a train state, and another was a free rotational motion of IPSOO protruding out from the MCC surface, defined as a tail state. The temperature of tumbling motion (T _tum ) of IPSOO at the train state was at 90 K with anisotropic correlation times. T _tum (90 K) is extremely low compared to the glass transition temperature (T _g ^b ; 373 K) of polystyrene in the bulk. At temperatures above 219 K, the IPSOO was protruded out from the MCC surface, and freely rotated at the tail state. The train–tail transition temperature (T _train–tail ) was estimated to be 222 K. T _tum (90 K) and T _train–tail (222 K) are due to the extremely low chain segmental density of IPSOO on the MCC surface under vacuum. The interaction between IPSOO and the MCC surface is a minor contributing factor in the mobility of IPSOO on the surface under vacuum. It was found that peroxy radicals are useful probes to characterize the chain mobility reflecting their environmental conditions.     

Antimicrobial activity of newly synthesized thienoquinolizidines derivatives: inspired by natural plant alkaloids

The antimicrobial activity of 16 newly prepared quinolizidines derivatives using bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Proteus sp., Escherichia coli) acid fast bacterium Mycobacterium smegmatis, yeasts (Candida albicans, Candida parapsilosis), and filamentous fungi (Fusarium culmorum, Microsporum gypseum, Aspergillus flavus, Botrytis cinerea, Alternaria alternata) was studied in this paper. The best antibacterial properties were demonstrated by derivatives 11Ba, trans10Bb and 11Bb, and the most sensitive microorganism was found to be the gram-positive bacterium S. epidermidis. The derivative 11Bb showed the best antifungal activity, while C. albicans was resistant to all tested derivatives, and C. parapsilosis was fully inhibited in the presence of the derivative 11Ba and 11Bb. Among the filamentous fungi, only the dermatophyte M. gypseum was partially inhibited. Biofilms represent the most prevalent type of microbial growth in nature and are crucial to the development of clinical infections. Newly synthesized derivatives were also added into the medium throughout the biofilm formation. We have observed a significant decrease of biofilm formation in the presence of quinolizidine derivatives, testifying to their significant antimicrobial activity. It seems that the relationship between antimicrobial activity and the structure is based on the alkaline character due to nitrogen, the saturated basic quinolizidine skeleton, and the position of sulfur in the molecule.     

Cycloaminomethylation of dihydric phenols catalyzed by <Emphasis Type="Italic">d</Emphasis>- and <Emphasis Type="Italic">f</Emphasis>-metal compounds

An efficient method has been developed for the synthesis of 7,16,25-triaryl-7,8,16,17,25,26-hexahydro-6H,15H,24H-tribenzo[f,m,t][1,5,8,12,15,19,3,10,17]hexaoxatriazacyclohenicosines, 3,8-diaryl-2,3,4,7,8,9-hexahydrobenzo[1,2-e:4,3-e′]bis[1,3]oxazines, 3,9-bis(chlorophenyl)-3,4,9,10-tetrahydro-2H,8H-benzo[1,2-e:3,4-e′]bis[1,3]oxazines, and 2,9-bis(chlorophenyl)-1,2,3,8,9,10-hexahydrobenzo[1,2-e:6,5-e′]bis-[1,3]oxazines via cycloaminomethylation of pyrocatechol, resorcinol, and hydroquinone with N,N-bis(methoxymethyl) anilines in the presence of samarium catalysts.