Two stages of treatments for upgrading bleached softwood paper grade pulp to dissolving pulp for viscose production

To convert bleached softwood paper grade pulp into dissolving pulp for viscose application, two stages of treatments consisting of enzymatic treatment and alkaline peroxide treatment were investigated. It was found that high reactivity (about 80%) of pulp could be achieved by endoglucanases (EG)-rich industrial cellulase treatment, and the α-cellulose content as well as the viscosity of enzymatically treated pulp can be further adjusted by the alkaline peroxide treatment with certain dosages of NaOH and H₂O₂ to finally meet the quality requirements of dissolving pulp. The resulting pulp with 68.7% of reactivity, 92.1% of α-cellulose content, and 506.9 mL/g of pulp viscosity could be obtained after the two stages of treatments. The appropriate dosage of EG-rich cellulase was 300 IU/g bone dry pulp in the stage of enzymatic treatment, while the suitable dosages of NaOH and H₂O₂ were 9 wt% and 1 wt%, respectively, in the stage of alkaline peroxide treatment.     

XRD studies of polyurethane elastomers based on chitin/1,4-butane diol blends

Chitin based polyurethane elastomers (PUEs) were synthesized by step growth polymerization techniques using poly (ε-caprolactone) (PCL), 4, 4′- diphenylmethane diisocyanate (MDI) and blends of chitin and 1,4-butanne diol (BDO). The conventional spectroscopic characterization of the samples with FT-IR, ¹H NMR and ¹³C NMR were in accordance with proposed PUEs structure. The crystalline behavior of the synthesized polymers were investigated by X-ray diffraction (XRD), differential scanning calorimetery (DSC), optical microscopic technique and loss tangent curves (tan δ peaks). Results showed that crystallinity of the synthesized PUEs samples was affected by varying the chitin contents used as chain extender. The contents of chitin favors the formation of more ordered structure, as higher peak intensities were obtained from the PU extended with chitin than 1,4-butane diol (BDO). X-ray diffraction experiments results correlates with optical microscopy findings. The higher ΔH value; 41.57 (J g^?1) was found in the samples extended with chitin than BDO (31.32 J g^?1).     

Oxidation of regenerated cellulose with NaClO2 catalyzed by TEMPO and NaClO under acid-neutral conditions

A new TEMPO-mediated oxidation with catalytic amounts of TEMPO and NaClO, and NaClO₂ as the primary oxidant under aqueous conditions at pH 3.5–6.8 was used to prepare water-soluble β-(1 → 4)-linked polyglucuronic acid Na salts (cellouronic acids, CUAs) with high molecular weight in good yield. When regenerated cellulose with original degree of polymerization (DP) of 680 was oxidized by the 4-acetamide-TEMPO/NaClO/NaClO₂ system at pH 5.8 and 40 °C for 3 days, CUA with weight average DP (DPw) of 490 was obtained quantitatively. No peaks other than six signals from β-(1 → 4)-linked anhydroglucuronic acid units of CUA were detected in the solution-state ¹³C NMR spectra of the oxidized products. Although the oxidized product prepared under the above conditions contained about 20% unoxidized cellulose particles, the non-CUA fraction was separable from CUAs by filtration or salt precipitation. The DPw values and yields of CUAs after the filtration or salt precipitation treatment were 250–380 and 45–71%, respectively.     

New antifungal scaffold derived from a natural pharmacophore: Synthesis of α-methylene-γ-butyrolactone derivatives and their antifungal activity against Colletotrichum lagenarium

Thirty new and thirty-four known analogues were designed and synthesized to improve the potential use of the α-methylene-γ-butyrolactone ring, a natural pharmacophore. All structures were confirmed by ¹H and ¹³C NMR, MS, and single-crystal X-ray diffraction analyses. The results of antifungal and cytotoxic activity indicated that the synthesized analogues showed significant inhibitory activity and limited selectivity. Compound 45 exhibited the highest antifungal activity with IC₅₀ = 22.8 μM but moderate cytotoxic activity with IC₅₀ = 28.5 μM (against BGC823 cell line) and 7.7 μM (against HeLa cell line). Analysis of structure–activity relationships revealed that the incorporation of an aromatic ring into the β, γ positions of the lactone ring improved antifungal activity, and that the introduction of electron-withdrawing groups into the aromatic rings increased the activity compared with electron-donating groups. The above results identified 4-phenyl-3-phenyl-2-methylenebutyrolactone (33) as a lead scaffold for discovering and developing novel and improved crop-protection agents.     

Immobilization of Candida rugosa lipase on electrospun cellulose nanofiber membrane

A biocatalyst with high activity retention of lipase was fabricated by the covalent immobilization of Candida rugosa lipase on a cellulose nanofiber membrane. This nanofiber membrane was composed of nonwoven fibers with 200 nm nominal fiber diameter. It was prepared by electrospinning of cellulose acetate (CA) and then modified with alkaline hydrolysis to convert the nanofiber surface into regenerated cellulose (RC). The nanofiber membrane was further oxidized by NaIO₄. Aldehyde groups were simultaneously generated on the nanofiber surface for coupling with lipase. Response surface methodology (RSM) was applied to model and optimize the modification conditions, namely NaIO₄ content (2–10 mg/mL), reaction time (2–10 h), reaction temperature (25–35 °C) and reaction pH (5.5–6.5). Well-correlating models were established for the residual activity of the immobilized enzyme (R² = 0.9228 and 0.8950). We found an enzymatic activity of 29.6 U/g of the biocatalyst was obtained with optimum operational conditions. The immobilized lipase exhibited significantly higher thermal stability and durability than equivalent free enzyme.     

Production of a new exopolysaccharide (EPS) by Pseudomonas oleovorans NRRL B-14682 grown on glycerol

Pure glycerol and glycerol-rich product (GRP) obtained from the biodiesel industries were used as carbon source for the production of a new extracellular polysaccharide (EPS) by Pseudomonas oleovorans NRRL B-14682. The influence of temperature (20–40 °C) and pH (6.0–8.0) was studied. A temperature of 30 °C and pH control at 6.8 gave the maximum cell growth and EPS production. The culture attained a maximum cell dry weight (CDW) of 9.55 g l⁻¹ and an EPS concentration of 11.82 g l⁻¹ when cultivated with pure glycerol. GRP was a suitable carbon source, as shown by the slightly higher EPS concentration (12.18 g l⁻¹). The EPS productivity obtained with GRP (3.85 g l⁻¹ d⁻¹) was almost twice that obtained with pure glycerol (2.00 g l⁻¹ d⁻¹). Also, the yield on glycerol was higher for the cultivation with GRP (0.36 g g⁻¹) than for pure glycerol (0.28 g g⁻¹). The EPS was a high molecular weight heteropolysaccharide, composed by neutral sugars (37–80 wt% galactose, 2–30 wt% glucose, 0.5–25 wt% mannose and 0.5–20 wt% rhamnose) and containing acyl group substituents (pyruvil, acetyl and succinyl were identified). The EPS forms highly viscous aqueous dispersions with many potential commercial applications.     

Adsorption of Cu(II), Cd(II), and Pb(II) from aqueous single metal solutions by mercerized cellulose and mercerized sugarcane bagasse chemically modified with EDTA dianhydride (EDTAD)

This work describes the preparation of new chelating materials derived from cellulose and sugarcane bagasse for adsorption of Cu²⁺, Cd²⁺, and Pb²⁺ ions from aqueous solutions. The first part involved the mercerization treatment of cellulose and sugarcane bagasse with NaOH 5 mol/L. Non- and mercerized cellulose and sugarcane bagasse were then reacted with ethylenediaminetetraacetic dianhydride (EDTAD) in order to prepare different chelating materials. These materials were characterized by mass percent gain, X-ray diffraction, FTIR, and elemental analysis. The second part consisted of evaluating the adsorption capacity of these modified materials for Cu²⁺, Cd²⁺, and Pb²⁺ ions from aqueous single metal solutions, whose concentration was determined by atomic absorption spectroscopy. These materials showed maximum adsorption capacities for Cu²⁺, Cd²⁺, and Pb²⁺ ions ranging from 38.8 to 92.6 mg/g, 87.7 to 149.0 mg/g, and 192.0 to 333.0 mg/g, respectively. The modified mercerized materials showed larger maximum adsorption capacities than modified non-mercerized materials.     

Green synthesis of a novel biodegradable copolymer base on cellulose and poly(p-dioxanone) in ionic liquid

A new cellulose graft copolymer was synthesized in 1-N-butyl-3-methylimidazolium chloride ([Bmim]Cl) by the ring opening graft polymerization (ROGP) of p-dioxanone (PDO) onto cellulose. The structure of the copolymer was characterized by ¹³C and ¹H NMR, WAXD, DSC as well as SEM. Cellulose graft copolymers with a molar substitution (MS) in the range of 2.08–4.60 were obtained with 24 h at 80 °C in a completely homogeneous procedure. The obtained copolymers exhibited the clear glass transition temperatures (T_g) indicating the inter-molecular and intra-molecular hydrogen bonds in cellulose molecules had been destroyed. The reaction media applied can be easily recycled and reused.     

Glucose biosensor based on glucose oxidase immobilized at gold nanoparticles decorated graphene-carbon nanotubes

Biopolymer pectin stabilized gold nanoparticles were prepared at graphene and multiwalled carbon nanotubes (GR-MWNTs/AuNPs) and employed for the determination of glucose. The formation of GR-MWNTs/AuNPs was confirmed by scanning electron microscopy, X-ray diffraction, UV–vis and FTIR spectroscopy methods. Glucose oxidase (GOx) was successfully immobilized on GR-MWNTs/AuNPs film and direct electron transfer of GOx was investigated. GOx exhibits highly enhanced redox peaks with formal potential of −0.40 V (vs. Ag/AgCl). The amount of electroactive GOx and electron transfer rate constant were found to be 10.5 × 10⁻¹⁰ mol cm⁻² and 3.36 s⁻¹, respectively, which were significantly larger than the previous reports. The fabricated amperometric glucose biosensor sensitively detects glucose and showed two linear ranges: (1) 10 μM – 2 mM with LOD of 4.1 μM, (2) 2 mM – 5.2 mM with LOD of 0.95 mM. The comparison of the biosensor performance with reported sensors reveals the significant improvement in overall sensor performance. Moreover, the biosensor exhibited appreciable stability, repeatability, reproducibility and practicality. The other advantages of the fabricated biosensor are simple and green fabrication approach, roughed and stable electrode surface, fast in sensing and highly reproducible.     

Probing the gel to liquid-crystalline phase transition and relevant conformation changes in liposomes by 13C magic-angle spinning NMR spectroscopy

A straightforward way to visualize gel to liquid-crystalline phase transition in phospholipid membranes is presented by using ¹³C magic-angle spinning NMR. The changes in the ¹³C isotropic chemical shifts with increasing temperature are shown to be a sensitive probe of the main thermotropic phase transition related to lipid hydrocarbon chain dynamics and relevant conformational changes. The average value of the energy difference between trans and gauche states in the central C4–11 fragment of the DMPC acyl chain was estimated to be 4.02 ± 0.2 kJ mol^− 1 in the liquid crystalline phase. The reported spectral features will be useful in ¹³C solid state NMR studies for direct monitoring of the effective lipid chain melting allowing rapid uniaxial rotation of membrane proteins in the biologically relevant liquid-crystalline phase.     

Structural elucidation and biological activity of a novel polysaccharide by alkaline extraction from cultured Cordyceps militaris

A novel polysaccharide named CBP-1 was isolated from the fruiting body of cultured Cordyceps militaris by alkaline extraction as well as anion-exchange and gel-permeation chromatography. Its structural features were investigated by a combination of chemical and instrumental analysis approaches, including partial hydrolysis, methylation analysis, HIO₄ oxidation-Smith degradation, GC–MS, ¹³C NMR, HPAEC-PAD and FT-IR. The results indicated that CBP-1 has a backbone of (1 → 4)-α-d-mannose residues which occasionally branches at O-3. The branches were mainly composed of (1 → 4)-α-d-glucose residues and (1 → 6)-β-d-galactose residues, and terminated with β-d-galactose residues. In the in vitro antioxidant assay, CBP-1 was found to possess the hydroxyl radical-scavenging activity with an IC₅₀ value of 0.638 mg/ml.     

Production of yeast chitin–glucan complex from biodiesel industry byproduct

Crude glycerol from the biodiesel industry was used as carbon source for high cell density fed-batch cultivation of Pichia pastoris aiming at producing a chitin–glucan complex (CGC). More than 100 g L^?1 biomass was obtained in less than 48 h. The yield of biomass on a glycerol basis was 0.55 g g^?1 during the batch phase and 0.63 g g^?1 during the fed-batch phase. The chitin–glucan complex was recovered from the yeast cell wall by hot alkaline extraction. CGC content in the cell wall was found to be relatively constant throughout the cultivation (18–26%) with a volumetric productivity of 1.28 g L^?1 h^?1 at the end of the fed-batch phase. The molar ratio of chitin:β-glucan in the extracted biopolymer was 16:84, close to other CGC extracted from Aspergillus biomass. The extracted polymer was characterized by Differential Scanning Calorimetry (DCS) and solid-state Nuclear Magnetic Resonance (NMR) spectroscopy and compared with commercial biopolymers, namely, crab shell chitin and/or chitosan, algal β-glucan (laminarin) and fungal chitin–glucan complex (kiOsmetine).     

Physicochemical characterization of chitin and chitosan from crab shells

Crab chitosan was prepared by alkaline N-deacetylation of crab chitin for 60, 90 and 120 min and the yields were 30.0-32.2% with that of chitosan C120 being the highest. The degree of N-deacetylation of chitosans (83.3–93.3%) increased but the average molecular weight (483–526 kDa) decreased with the prolonged reaction time. Crab chitosans showed lower lightness and WI values than purified chitin, chitosans CC and CS but higher than crude chitin. With the prolonged reaction time, the nitrogen (8.9–9.5%), carbon (42.2–45.2%) and hydrogen contents (7.9–8.6%) in chitosans prepared consistently increased whereas N/C ratios remained the same (0.21). Crab chitosans prepared showed a melting endothermic peak at 152.3–159.2 °C. Three chitosans showed similar microfibrillar crystalline structure and two crystalline reflections at 2θ = 8.8–9.0° and 18.9–19.1°. Overall, the characteristics of three crab chitosans were unique and differed from those of chitosan CC and CS as evidenced by the element analysis, differential scanning calorimetry, scanning electron microscopy and X-ray diffraction patterns.     

Extracellular biosynthesis of silver nanoparticles using Rhizopus stolonifer

Synthesis of silver nanoparticles (AgNPs) has become a necessary field of applied science. Biological method for synthesis of AgNPs by Rhizopus stolonifer aqueous mycelial extract was used. The AgNPs were identified by UV–visible spectrometry, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectrometry (FT-IR). The presence of surface plasmon band around 420 nm indicates AgNPs formation. The characteristic of the AgNPs within the face-centered cubic (fcc) structure are indicated by the peaks of the X-ray diffraction (XRD) pattern corresponding to (1 1 1), (2 0 0) and (2 2 0) planes. Spherical, mono-dispersed and stable AgNPs with diameter around 9.47 nm were prepared and affirmed by high-resolution transmission electron microscopy (HR-TEM). Fourier Transform Infrared (FTIR) shows peaks at 1426 and 1684 cm⁻¹ that affirm the presence of coat covering protein the AgNPs which is known as capping proteins. Parameter optimization showed the smallest size of AgNPs (2.86 ± 0.3 nm) was obtained with 10⁻² M AgNO₃ at 40 °C. The present study provides the proof that the molecules within aqueous mycelial extract of R. stolonifer facilitate synthesis of AgNPs and highlight on value-added from R. stolonifer for cost effectiveness. Also, eco-friendly medical and nanotechnology-based industries could also be provided. Size of prepared AgNPs could be controlled by temperature and AgNO₃ concentration. Further studies are required to study effect of more parameters on size and morphology of AgNPs as this will help in the control of large scale production of biogenic AgNPs.     

Isolation,identification, and bioactivity of microbial metabolites of cyclopamine and its congeners

The biotransformation of cyclopamine (1) and its congeners (2, 3 and 4) by Cunninghamella echinulata (ACCC 30369) was investigated. The chemical structures of two new congeners (2 and 4) and nine new metabolites were elucidated by 1D NMR (¹H, ¹³C and DEPT), 2D NMR (COSY, HMBC, HSQC and NOESY) and HRESIMS analyses and further confirmed by X-ray diffraction studies. Among these compounds, 2 and 4 showed moderate cytotoxicity in HepG2 cells (2, IC₅₀ = 8.03 ± 1.92 μM) and A549 cells (4, IC₅₀ = 10.19 ± 2.18 μM). Conversely, the cytotoxicity of the nine metabolites was sharply reduced. Similar to 1, compound 4 induced a cyclopia phenotype in zebrafish embryos at 20 μM. Moreover, compound 4 was more stable than 1 in an acidic environment.     

Immobilization of acidic lipase derived from Pseudomonas gessardii onto mesoporous activated carbon for the hydrolysis of olive oil

Mesoporous activated carbon (MAC) derived from rice husk is used for the immobilization of acidic lipase (ALIP) produced from Pseudomonas gessardii. The purified acidic lipase had the specific activity and molecular weight of 1473 U/mg and 94 kDa respectively. To determine the optimum conditions for the immobilization of lipase onto MAC, the experiments were carried out by varying the time (10–180 min), pH (2–8), temperature (10–50 °C) and the initial lipase activity (49 × 10³, 98 × 10³, 147 × 10³ and 196 × 10³ U/l in acetate buffer). The optimum conditions for immobilization of acidic lipase were found to be: time—120 min; pH 3.5; temperature—30 °C, which resulted in achieving a maximum immobilization of 1834 U/g. The thermal stability of the immobilized lipase was comparatively higher than that in its free form. The free and immobilized enzyme kinetic parameters (K_m and V_max) were found using Michaelis–Menten enzyme kinetics. The K_m values for free enzyme and immobilized one were 0.655 and 0.243 mM respectively. The immobilization of acidic lipase onto MAC was confirmed using Fourier Transform-Infrared Spectroscopy, X-ray diffraction analysis and scanning electron microscopy.     

Ability of a perfluoropolymer membrane to tolerate by-products of ethanol fermentation broth from dilute acid-pretreated rice straw

A perfluoropolymer (PFP) membrane has been prepared for use in vapor permeation to separate aqueous ethanol mixtures produced from rice straw with xylose-assimilating recombinant Saccharomyces cerevisiae. PFP membranes commonly have been used for dehydration process and possess good selectivity and high permeances. The effects of by-products during dilute acid pretreatment, addition of yeast extract, and ethanol fermentation on PFP membrane performance were investigated. While feeding mixtures of ethanol (90 wt%) in water, to which individual by-products (0.1–2 g/L) were added, the PFP membrane demonstrated no clear change in permeation rate (439–507 g m⁻² h⁻¹) or separation factor (14.9–23.5) from 2 to 4 h of the process. The PFP membrane also showed no clear change in permeation rate (751–859 g m⁻² h⁻¹) or separation factor (12.5–13.8) while feeding the mixture (final ethanol conc.: 61 wt%) of ethanol and distillation of the fermentation broth using a suspended fraction of dilute acid-pretreated rice straw for 20 h. These results suggest that the PFP membrane can tolerate actual distillation liquids from ethanol fermentation broth obtained from lignocellulosic biomass pretreated with dilute acid.     

Synthesis,X-ray crystal structure,DNA/protein binding and cytotoxicity studies of five α-aminophosphonate N-derivatives

Five new α-aminophosphonates are synthesized and characterized by EA, FT-IR, ¹H NMR, ¹³C NMR, ³¹P NMR, ESI-MS and X-ray crystallography. The X-ray analyses reveal that the crystal structures of 1–5 are monoclinic or triclinic system with the space group P 21/c, P − 1, P − 1, P2(1)/c and P − 1, respectively. All P atoms of 1–5 have tetrahedral geometries involving two O-ethyl groups, one C_α atom, and a double bond O atom. The binding interaction of five new α-aminophosphonate N-derivatives (1–5) with calf thymus(CT)-DNA have been investigated by UV–visible and fluorescence emission spectrometry. The apparent binding constant (Kapp) values follows the order: 1 (3.38 × 10⁵ M⁻¹) > 2 (3.04 × 10⁵ M⁻¹) > 4 (2.52 × 10⁵ M⁻¹) > 5 (2.32 × 10⁵ M⁻¹) > 3 (2.10 × 10⁵ M⁻¹), suggesting moderate intercalative binding mode between the compounds and DNA. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with the compounds 1–5 showed that the quenching mechanism might be a static quenching procedure. For the compounds 1–5, the number of binding sites were about one for BSA and the binding constants follow the order: 1 (2.72 × 10⁴ M⁻¹) > 2 (2.27 × 10⁴ M⁻¹) > 4 (2.08 × 10⁴ M⁻¹) > 5 (1.79 × 10⁴ M⁻¹) > 3 (1.17 × 10⁴ M⁻¹). Moreover, the DNA cleavage abilities of 1 exhibit remarkable changes and the in vitro cytotoxicity of 1 on tumor cells lines (MCF-7, HepG2 and HT29) have been examined by MTT and shown antitumor effect on the tested cells.     

Synthesis and in silico studies of novel sulfonamides having oxadiazole ring: As β-glucuronidase inhibitors

Novel sulfonamides having oxadiazole ring were synthesized by multistep reaction and evaluated to check in vitro β-glucuronidase inhibitory activity. Luckily, except compound 13, all compounds were found to demonstrate good inhibitory activity in the range of IC₅₀ = 2.40 ± 0.01–58.06 ± 1.60 μM when compared to the standard d-saccharic acid 1,4-lactone (IC₅₀ = 48.4 ± 1.25 μM). Structure activity relationship was also presented. However, in order to ensure the SAR as well as the molecular interactions of compounds with the active site of enzyme, molecular docking studies on most active compounds 19, 16, 4 and 6 was carried out. All derivatives were fully characterized by ¹H NMR, ¹³C NMR and EI-MS spectroscopic techniques. CHN analysis was also presented.     

Thiadiazole derivatives as New Class of β-glucuronidase inhibitors

Thiadiazole derivatives 1–24 were synthesized via a single step reaction and screened for in vitro β-glucuronidase inhibitory activity. All the synthetic compounds displayed good inhibitory activity in the range of IC₅₀ = 2.16 ± 0.01–58.06 ± 1.60 μM as compare to standard d-saccharic acid 1,4-lactone (IC₅₀ = 48.4 ± 1.25 μM). Molecular docking study was conducted in order to establish the structure–activity relationship (SAR) which demonstrated that thiadiazole as well as both aryl moieties (aryl and N-aryl) involved to exhibit the inhibitory potential. All the synthetic compounds were characterized by spectroscopic techniques ¹H, ¹³C NMR, and EIMS.