Immobilization and Stabilization of Beta-Xylosidases from Penicillium janczewskii

β-Xylosidases are critical for complete degradation of xylan, the second main constituent of plant cell walls. A minor β-xylosidase (BXYL II) from Penicillium janczewskii was purified by ammonium sulfate precipitation (30% saturation) followed by DEAE-Sephadex chromatography in pH 6.5 and elution with KCl. The enzyme presented molecular weight (MW) of 301 kDa estimated by size exclusion chromatography. Optimal activity was observed in pH 3.0 and 70–75 °C, with higher stability in pH 3.0–4.5 and half-lives of 11, 5, and 2 min at 65, 70, and 75 °C, respectively. Inhibition was moderate with Pb⁺² and citrate and total with Cu⁺², Hg⁺², and Co⁺². Partially purified BXYL II and BXYL I (the main β-xylosidase from this fungus) were individually immobilized and stabilized in glyoxyl agarose gels. At 65 °C, immobilized BXYL I and BXYL II presented half-lives of 4.9 and 23.1 h, respectively, therefore being 12.3-fold and 33-fold more stable than their unipuntual CNBr derivatives (reference mimicking soluble enzyme behaviors). During long-term incubation in pH 5.0 at 50 °C, BXYL I and BXYL II glyoxyl derivatives preserved 85 and 35% activity after 25 and 7 days, respectively. Immobilized BXYL I retained 70% activity after 10 reuse cycles of p-nitrophenyl-β-D-xylopyranoside hydrolysis.

     

Addition of Surfactants and Non-Hydrolytic Proteins and Their Influence on Enzymatic Hydrolysis of Pretreated Sugarcane Bagasse

Poly(ethylene glycol) (PEG 4000) and bovine serum albumin (BSA) were investigated with the purpose of evaluating their influence on enzymatic hydrolysis of sugarcane bagasse. Effects of these supplements were assayed for different enzymatic cocktails (Trichoderma harzianum and Penicillium funiculosum) that acted on lignocellulosic material submitted to different pretreatment methods with varying solid (25 and 100 g/L) and protein (7.5 and 20 mg/g cellulose) loadings. The highest levels of glucose release were achieved using partially delignified cellulignin as substrate, along with the T. harzianum cocktail: increases of 14 and 18 % for 25 g/L solid loadings and of 33 and 43 % for 100 g/L solid loadings were reached for BSA and PEG supplementation, respectively. Addition of these supplements could maintain hydrolysis yield even for higher solid loadings, but for higher enzymatic cocktail protein loadings, increases in glucose release were not observed. Results indicate that synergism might occur among these additives and cellulase and xylanases. The use of these supplements, besides depending on factors such as pretreatment method of sugarcane bagasse, enzymatic cocktails composition, and solid and protein loadings, may not always lead to positive effects on the hydrolysis of lignocellulosic material, making it necessary further statistical studies, according to process 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.     

Swelling behaviors of poly(dodecyl methacrylate-co-methyl eugenol) and poly(dodecyl methacrylate-co-methyl chavicol) gels in essential oil components

Poly(dodecylmethacrylate-co-methyleugenol) P(DDMA-co-Meu) and poly(dodecylmethacrylate-co-methylchavicol) P(DDMA-co-Mch) gels were synthesized in ethanol using free radical cross-linking polymerization method at 60 °C for 24 h in the presence of azobisisobutyronitrile (AIBN) and triethylene glycol dimethacrylate (TEGDMA) as initiator and cross-linker, respectively. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the gels. These gels were used to investigate swelling behaviors in linalool and methyl eugenol, in essential oil mixture of phenyl propanoid and terpenoid, and also in various solvents. While the equilibrium swelling values (ESV) of both gels were higher in linalool than in methyl eugenol, the result was vice versa in the case of essential oil mixture. ESVs of both gels were also obtained in various solvents with different functional groups and the highest ESV of both gels were obtained in toluene, and the lowest ESV of P(DDMA-co-Meu) and P(DDMA-co-Mch) was in methanol and in ethylene glycol, respectively. While P(DDMA-co-Meu) is sensitive to carbon number change in alcohol, P(DDMA-co-Mch) is less sensitive. In the case of esters, increase of carbon number in functional group causes a more significant change in ESV than an increase of carbon number in aliphatic chain. Experimental results were correlated by the first-order and second-order models. The second-order model was more suitable than the other. While P(DDMA-co-Meu) gel swelled in linalool exhibits a Fickian diffusion character, the diffusion mechanism of the gel in methyl eugenol is a non-Fickian one. In the case of P(DDMA-co-Mch), the result is vice versa.     

Utilization of GDOES for the study of friction layers formed on the surface of brake discs during the friction process

The paper deals with the chemical characterization of friction layer, generated on the surface of friction materials during the friction test using the glow discharge optical emission spectrometry (GDOES). Friction layer is formed during the friction process and its character depends on several factors. One of the most important factors is the material composition of brake pads and brake disc. When the brake pressure is released at the end of the braking event, the specific friction layer remains on the surface of both pairs (brake pads and brake disc). Using the GDOES profile analysis, the thicknesses of friction layers were estimated and these results were compared with results obtained by scanning electron microscopy together with X-ray microanalysis.     

Fluorene-containing tetraphenylethylene molecules as lasing materials

A series of star-shaped oligofluorene molecules, each containing a TPE core, have been specifically designed and produced to show effective aggregation-induced emission (AIE). Each molecule differs either in the number of fluorene units within the arms (e.g., 1 or 4, compounds 4 and 5 ), or the terminal group positioned at the end of each arm (e.g., H, TMS, or TPA, compounds 4 , 6 , and 7 ). Although they are all poor emitters in solution phase they become efficient yellow-green luminogens in the condensed state. Their AIE properties were investigated in THF/H₂O mixtures, with each molecule exhibiting a clear emission enhancement at specific water contents. An all-organic distributed feedback (DFB) laser was fabricated using compound 4 as the gain material and exhibited an average threshold energy fluence of 60 ± 6 μJ/cm² and emission in the green region. Furthermore, piezofluorochromism studies on a thin film of this material displayed a linear dependence of the amplified spontaneous emission (ASE) peak position on applied pressure, indicating potential applications as lasing-based pressure sensors. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 734–746     

Mechanically-induced dimensional extensibility of fibers towards tough fiber networks

The beneficial effect of materials with high aspect ratio as composite reinforcement has prompted continuous interest towards cellulosic fibers. Besides providing stiffness, fibers can potentially contribute to composite extensibility. While mechanical treatments are typically used to adjust the physical and surface properties of fibers, less is known about ensuing effects on their extensibility and that of associated networks. Fiber network dimensional extensibility of 16% was achieved by processing the precursor aqueous fiber dispersions following a simple mechanical treatment with a judicious combination of low (PFI refining) and high concentrations and temperatures (Wing defibrator). Consequently, deformation of fibers and increased inter-fiber bonding resulted in a three-fold increase in strength to rupture of the fiber network leading to the structures with unprecedented toughness.     

Analysis of moisture sorption in lyocell-polypropylene composites

The preparation of composites by thermoforming of intermingled fibre slivers is an efficient method to receive high performance and lightweight materials. Cellulosic fibres have benefits like low density and sustainability but the sorption of water due to the high hydrophilicity of the cellulose requires attention. The swelling of the wet fibres changes the fibre-matrix adhesion and as a consequence, the mechanical strength of the composite is influenced negatively. In this study, the thermoplastic polypropylene was combined with lyocell fibres as reinforcement. Moisture sorption isotherms of cellulose/polypropylene composites were recorded as function of relative humidity. Additionally, the specific surface area was analysed by the Brunauer–Emmett–Teller model. It has been found, that the moisture sorption is influenced by the polypropylene (PP) ratio in the composites. At 60% relative humidity the moisture uptake of the lyocell fibres was reduced from 10.8 to 5.8% for lyocell embedded in a composite with 50% polypropylene. Besides the hysteresis between moisture sorption/desorption cycles was found to be proportional to the increased content of PP. The “Parallel Exponential Kinetics” (PEK) model was used to analyse the kinetics of moisture sorption of these composites in more detail. With the help of the PEK model the sorption/desorption kinetics were described by a fast and slow moisture sorption/desorption process. The capacity for rapid moisture sorption is reduced by the formation of PP layers on the lyocell surface. The share of slow moisture sorption increased with increasing PP content in the composite. The results support understanding of the interaction of water with cellulose containing composites.     

Study of oriented polyethylene structures using a Raman longwave acoustic mode

This paper concerns the basics of using longwave (low-frequency) Raman spectroscopy in the region of a longitudinal acoustic mode for the study of structural features of polymers. Using ultrahighmolecular- weight polyethylene (UHMW PE)-based reactor powders, gels, and oriented fibers obtained by the gel technology, the length distribution of straight-chain segments and its relation to the morphology of the sample were analyzed. An important role of the low-frequency Raman spectroscopy in creating domestic gel technology for preparing ultrahigh-strength threads from polyethylene was demonstrated.