Excellent Thermostability Research Articles

Characterization and efficient production of a thermostable, halostable and organic solvent-stable cellulase from an oil reservoir

The manufacture of biofuels from cellulose is regarded as one of practicable strategies to meet increasing energy demand and alleviate environmental issues. Cellulases, which play an important role in the production of second-generation biofuels, are expected to be highly thermostable, halostable and organic solvent-stable to adapt to the harsh conditions in practical application. Here we cloned and characterized a novel cellulase (MaCel) from Mahella australiensis 50-1 BON, an anaerobic thermophile isolated from an oil reservoir. MaCel exhibited excellent thermostability, halostability as well as organic solvent stability, and could be efficiently produced in a yield of 1.7 × 106 U/L in 15 h with inexpensive culture medium. These results indicate that MaCel may be a suitable candidate for industrial applications, illustrating the potential benefits of enzymes from oil reservoir extremophiles in the manufacture of biofuels.

A waterborne superLEphilic and thermostable separator based on natural clay nanorods for high-voltage lithium-ion batteries

Commercial separators for lithium-ion batteries still have shortcomings such as inferior electrolyte wettability, serious thermal shrinkage (polyolefin separators) and intrinsic brittleness (ceramic separators), which result in poor electrochemical performance and serious potential safety hazard. Here, a waterborne separator is fabricated by deposition and in situ crosslinking of a homogeneous aqueous suspension containing natural clay nanorods (attapulgite, ATP) and polyvinylalcohol (PVA) onto both the external and internal surfaces of the Celgard@2400 matrix. Different from conventional grafted or coated functional separators, the ATP-PVA/Celgard separator has a unique sandwiching/infusing structure. The separator features super-electrolyte-philicity with a liquid electrolyte contact angle of 0°, high Li+ conductivity (0.782 mS cm−1), excellent mechanical properties and high thermostability. Consequently, the 4.9 V Li/LiNi0.5Mn1.5O4 cell with the separator shows higher cycling stability (94.7% after 100 cycles), better rate performance and lower resistance than the cell with commercial ceramic separator. Moreover, the separator could improve performance of the Li/LiFePO4 cell and stable open circuit voltage at 160 °C. This work provides an avenue for the design of advanced separators for high-voltage lithium-ion batteries via an environmentally friendly method using natural nanomaterials.

Effect of pendent phenyl and bis-phthalazinone moieties on the properties of N-heterocyclic poly(aryl ether ketone ketone)s

A series of novel N-heterocyclic copoly (aryl ether ketone ketone)s containing pendent phenyl groups and bis-phthalazinone moieties (P-BNP) with high molecular weight were successfully synthesized via solution condensation from 4-(3′-phenyl-4′-hydroxyphenyl)-2,3-phthalazin-1-one, 4,4′-di(4′-1(2H)-phthalazinone)-1,1′-biphenyl and 1,4-bis(4′-fluorobenzoyl)benzene. The properties of P-BNPs were identified by thermogravimetric analysis (TGA), differential scanning calorimetry analysis (DSC), and dynamic thermomechanical analysis (DMA) etc. The polymer exhibits excellent thermo-stability in both nitrogen and air. The glass-transition temperature (Tg) is in the range of 240–290 °C, copolymers performing a presentable thermo-resistance. Moreover, copolymers can be dissolved in chloroform and N-methyl-2-pyrrolidone (NMP), exhibiting excellent film-forming property. Simultaneously, copolymers possess favorable mechanical properties. The introduction of pendent phenyl moieties enhances the mobility of molecular chains and solubility of copolymers. The introduction of rigid bis-phthalazinone units enhances the thermo-resistance and mechanical properties of copolymers. Rational allocation of rigid units and side groups content will optimize the comprehensive properties of high-performance polymers.

Structural characterization and physicochemical properties of arrowhead resistant starch prepared by different methods

Resistant starch (RS) served as a novel functional ingredient has attracted much attention. In this paper, the structure and physicochemical properties of arrowhead resistant starch (ARS) prepared by subcritical water (SW-ARS), ultrasound-subcritical water (USW-ARS), autoclaving (AM-ARS) and ultrasound-autoclaving (UAM-ARS) were investigated. The results showed that the structure of starch granules was completely disrupted and the size of starch granules was obviously increased. SW-ARS, USW-ARS, AM-ARS and UAM-ARS exhibited a B-type crystallinity pattern with different degree of crystallinity. UAM-ARS displayed the highest molecular order with the highest degree of double helixes while SW-ARS, USW-ARS and AM-ARS showed a lower degree of molecular order than that of arrowhead native starch (ANS). The ANS and ARS prepared by four methods possessed high gelation enthalpy in which UAM-ARS had the highest gelation enthalpy, indicating that they had excellent thermostability. Therefore, ANS and the resulting ARS may be a promising starch-based material. All these results are expected to provide information on the preparation and application of ANS and ARS.

Low-temperature growth of Three dimensional ReS2/ReO2 metal-semiconductor heterojunctions on Graphene/polyimide film for enhanced hydrogen evolution reaction

Flexible inorganic electronics (FIE) have shown unique advantages in energy conversion, aerospace and wearable devices due to excellent electronic properties and thermostability of inorganic materials. The industrialization of high-performance flexible inorganic electronics (FIE) devices requires universal approaches to fabricate inorganic crystal on polymer substrates at acceptable temperature. Herein, we firstly developed the vortex flow chemical vapor deposition (VFCVD) for low temperature synthesis of high-quality vertical ReO2 arrays at 450 °C on flexible graphene-polyimide (G-PI) conductive film. The Euler equations suggest that the vapor pressure of ReO2 is almost 100-times higher than that of free space with VFCVD at identical conditions. The derived ReS2/ReO2 metal-semiconductor heterojunction arrays are performed outstanding hydrogen evolution reaction (HER) activity with high long-term stability as an energy conversion device. This work opens up an opportunity for low temperature growth of inorganic nanomaterials on polymer substrates by VFCVD for the industrialization of high-performance flexible energy devices.

Expression and characterization of a CALB-type lipase from Sporisorium reilianum SRZ2 and its potential in short-chain flavor ester synthesis

A lipase from Sporisorium reilianum SRZ2 (SRL) with 73% amino acid sequence identity to Candida antarctica lipase B (CALB) was cloned and overexpressed in Pichia pastoris. The recombinant SRL showed a preference for short-chain p-nitrophenyl esters. It achieved maximum activity at pH 8.0 and 65°C for p-nitrophenyl hexanoate (C6) with Km and kcat/Km values of 0.14 mmol·L−1 and 1712 min−1 · mmol · L−1 at 30°C, respectively. SRL displayed excellent thermostability and pH stability, retaining more than 79% of its initial activity after incubation at 60°C for 72 h and 75% at pH 3 to 11 for 72 h. It also maintained most of its activity in the presence of inhibitors and detergents except sodium dodecyl sulfate, and it tolerated organic solvents. SRL was covalently immobilized and successfully used for ethyl hexanoate synthesis in cyclohexane or in a solvent-free system with a high conversion yield (> 95%). Furthermore, high conversion yield was also achieved for the synthesis of various short-chain flavor esters when high substrate concentrations of 2 mol · L−1 were applied. This study indicated that a CALB-type lipase from S. reilianum SRZ2 showed great potential in organic ester synthesis.

A bio-resourced mannitol phospholipid ammonium reactive flame retardant for cotton with efficient antiflaming and durability

Bio-resourced mannitol was employed to synthesize eco-friendly ammonium salt of mannitol hexaphosphate acid ester (AMHPE) by facile, solvent-free tactics. Limiting oxygen index (LOI) of cotton treated with 20–30% AMHPE reached 36.0–42.3% to obtain high-efficiency flame retardancy. After 50 laundering cycles, the LOI value of 30% AMHPE treated cotton still retains an LOI value of 27.9%, revealing outstanding durability owing to new P–O–C covalent bonds formed bewteen –P = O(ONH4)2+ groups of AMHPE and cotton. The decomposition temperature of treated cotton was significantly lowered and its char residue was much higher than control cotton in N2. The PHRR and THR values of treated cotton were notably declined to 93.41% and 56.54% respectively, and the residual is 28 times higher by contrast. The combustion products and flame retardant mechanism of treated cotton were analyzed by TG-IR and cone calorimetry. These results indicate that AMHPE flame retardant cotton has acquired efficient flame retardancy, excellent durability and thermostability. Solvent-free synthesis of bio-resourced N–P synergetic flame retardant possessing excellent flame retardancy, unexceptionable durability and thermostability to reduce cotton fire hazard.

Altered Cofactor Preference of Thermostable StDAPDH by a Single Mutation at K159.

D-amino acid production from 2-keto acid by reductive amination is an attractive pathway because of its high yield and environmental safety. StDAPDH, a meso-diaminopimelate dehydrogenase (meso-DAPDH) from Symbiobacterium thermophilum, was the first meso-DAPDH to show amination of 2-keto acids. Furthermore, StDAPDH shows excellent thermostability compared to other meso-DAPDHs. However, the cofactor of StDAPDH is NADP(H), which is less common than NAD(H) in industrial applications. Therefore, cofactor engineering for StDAPDH is needed. In this study, the highly conserved cofactor binding sites around the adenosine moiety of NADPH were targeted to determine cofactor specificity. Lysine residues within a loop were found to be critical for the cofactor specificity of StDAPDH. Replacement of lysine with arginine resulted in the activity of pyruvic acid with NADH as the cofactor. The affinity of K159R to pyruvic acid was equal with NADH or NADPH as the cofactor, regardless of the mutation. Molecular dynamics simulations revealed that the large steric hindrance of arginine and the interaction of the salt bridge between NADH and arginine may have restricted the free movement of NADH, which prompted the formation of a stable active conformation of mutant K159R. These results provide further understanding of the catalytic mechanism of StDAPDH and guidance for the cofactor engineering of StDAPDH.

Flexible room-temperature gas sensor based on poly (para-phenylene terephthalamide) fibers substrate coupled with composite NiO@CuO sensing materials for ammonia detection

Flexible chemiresistor-type sensor based on chemically sensitive oxide semiconductors is of great potential for wearable sensing field. It is still challenging in designing sensing materials with high electron mobility for the enhancement of sensitivity and developing flexible chemical sensors with high durability for commercial applications. Herein, we introduce that poly (para-phenylene terephthalamide) fibers, which are currently employed as substrate to support the composite NiO@CuO metal oxide semiconductors. The poly (para-phenylene terephthalamide)-NiO@CuO gas sensor exhibits excellent thermostability, with rarely changing in mass observed up to 450 °C of high temperature testing. Furthermore, a relatively low limit of detection of 46.5 ppb for NH3 is achieved at room temperature. The gas sensing mechanism of the sensing materials is interpreted via the electron-mobility-dominating gas sensing mode, in which the hole density is directly influenced via the electrons transferring between gas molecules and sensing materials. These results of the chemical gas sensor provide great promising for developing sensing materials with highly sensitivity and unlock the potential for newly-designed flexible chemiresistor-type sensor in the field of wearable sensing applications.

Kinetic and thermodynamic parameters of nisin thermoinactivation

Understanding the thermal inactivation of biopreservatives in food matrixes is essential for their proper use in the food industry, enabling reduction of heating time and optimization of heating temperature. With this aim in mind, the effect of heat treatment on the activity and thermostability of commercial nisin from Lactococcus lactis was investigated. Residual activity tests performed for 90 min in the 70–86 °C temperature range at pH 3.0 demonstrated that bacteriocin thermoinactivation followed first-order kinetics. Low values of the inactivation rate constant (0.0089–0.0892 min−1) and high values of the decimal reduction time (25.8 ≤ D-value ≤ 258.4 min) indicated excellent nisin thermostability in the lower end of the investigated temperature range, but the thermal resistance constant (z-value) was only 15.4 °C, which pointed out poor thermoresistance at the higher end. Thermodynamic parameters estimated for nisin irreversible thermal inactivation were energy, enthalpy and Gibbs free energy of activation of 155.1, 152.2–152.3 and 83.5–86.6 kJ mol−1, respectively, and activation entropy of 188.6–192.5 J mol−1 K−1. If on the one hand these results taken together confirm the thermostability of nisin as a biopreservative in use in the food industry, on the other hand suggest the importance of looking for new more thermostable antimicrobials to use in operations at higher temperatures.

Evaluation of Second-Generation Lipophosphonoxins as Antimicrobial Additives in Bone Cement.

Successful surgeries involving orthopedic implants depend on the avoidance of biofilm development on the implant surface during the early postoperative period. Here, we investigate the potential of novel antibacterial compounds—second-generation lipophosphonoxins (LPPOs II)—as additives to surgical bone cements. We demonstrate (i) excellent thermostability of LPPOs II, which is essential to withstand elevated temperatures during exothermic cement polymerization; (ii) unchanged tensile strength and elongation at the break properties of the composite cements containing LPPOs II compared to cements without additives; (iii) convenient elution kinetics on the order of days; and (iv) the strong antibiofilm activity of the LPPO II-loaded cements even against bacteria resistant to the medicinally utilized antibiotic, gentamicin. Thus, LPPOs II display promising potential as antimicrobial additives to surgical bone cements.

GO-modified double-walled polyurea microcapsules/epoxy composites for marine anticorrosive self-healing coating

In order to achieve microcapsules' higher encapsulating capacity and better self-healing efficiency, the graphene oxide (GO)-modified double-walled Polyurea microcapsules were synthesized with 1, 6-Diaminohexane as the inner core and isophorone diisocyanate (IPDI)-based prepolymer as the outer core. Measured were the morphology, structure, thermal property and mechanical property of the microcapsules by using the Optical and Scanning Electron Microscopy (OM, SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Nanoindentation tests. And the mechanical testing machine, Digital Speckle Correlation Method (DSCM) and Electrochemical Impedance Spectroscopy (EIS) measurement were used to evaluate their mechanical and anticorrosive properties. The results showed that the GO-modified microcapsules obtained possessed a good spherical shape with a mean diameter of 0.5 μm. The microcapsules with excellent thermostability containing a urea bond, the GO had been successfully embedded into the wall materials and the contents of the inner core materials and outer core materials were 26.75 wt% and 10.88 wt% respectively. The average Young's modulus, hardness and load during the holding time of the microcapsules were 2.708GPa, 0.088GPa and 28.51mN respectively. The mechanical and anticorrosive self-healing efficiency of epoxy coating with 3.0 wt% of microcapsules could gain up to 80.43% and 62.50% respectively.

Bio-inspired fabrication of nacre-mimetic hybrid nanocoating for eco-friendly fire-resistant precious cellulosic Chinese Xuan paper

Nacre-mimetic materials possess excellent thermostability and barrier performance which provide novel idea for high efficient flame retardant strategy. In this study, we propose an eco-friendly approach to fabricate fire-resistant cellulosic Chinese Xuan paper by layer-by-layer (LBL) assembly chitosan (CH) and montmorillonite (MMT). The flame retardancy of Xuan paper was greatly improved after the LBL assembly coated CH/MMT, it achieved excellent flame retardancy when the CH/MMT bilayer was over 10 BL with the LOI value higher than of 35 %. The results of thermal stability of treated Xuan paper revealed the nacre-mimetic CH/MMT nanocoating on Xuan paper would promote the formation of compact and dense char which will be beneficial to inhibit the heat transmission and combustible gas diffusion. The ink wetting performance was also investigated in this study. This research would provide experimental basis for the development of fire-resisting paper using bio-mimetic method to construct nacre-mimetic organic/inorganic hybrid flame retardant system.

One-pot synthesis of HMF from carbohydrates over acid-base bi-functional carbonaceous catalyst supported on halloysite nanotubes

Nitrogen-doped carbon materials have attracted enormous interest in catalysis owing to their outstanding catalytic performance. In this work, nitrogen-doped carbonaceous catalysts (NCC) supported on inexpensive and naturally abundant halloysite nanotubes were successfully synthesized via precipitation polymerization, calcination, and sulfonation processes. The physical and chemical properties of the obtained catalysts were systematically characterized by different methods. The results indicated that NCC catalysts had mesoporous structures, excellent thermostability and acid-base bi-functional active sites. One-pot synthesis of 5-hydroxymethylfurfural (HMF) from glucose was performed to investigate the synthesized NCC catalysts. Benefiting from the synergistic effects of the acid-base bi-functional active sites, the highest HMF yield (62.8%) was achieved in an isopropanol-mediated DMSO system under optimal conditions. Moderate to excellent yields of HMF were also obtained from one-pot conversions of other carbohydrates, including inulin, sucrose, cellobiose, maltose and starch, with our developed catalytic system. The one-pot production of HMF from cellulose was also smoothly processed by the NCC bi-functional catalyst in an IL-based system. This work has developed a versatile strategy for designing nitrogen-doped carbonaceous catalysts that can be employed for the direct transformation of renewable carbohydrates to platform chemicals.

Superelastic EGaIn Composite Fibers Sustaining 500% Tensile Strain with Superior Electrical Conductivity for Wearable Electronics.

Stretchable conductive fibers have gained significant attention in the field of wearable and flexible electronics because of their inherited unique properties. Up to now, there are few reports regarding the highly stretchable fibers with excellent electronic properties. In this work, a highly stretchable fiber with superior electrical conductivity is fabricated, which contains a core fiber, an intermediate modified layer, and an outer eutectic-gallium-indium liquid metal layer. The fiber demonstrates an excellent electrical conductivity of over 103 S cm-1 when stretched up to 500% strain, which is far superior to the existing stretchable conductive fiber. The stretchable conductive fiber shows excellent thermostability with a maximum operating temperature of nearly 250 °C. Such unique fibers can be applied as highly stretchable, deformable conductor to charge a mobile phone, and sensor to monitor human activities. This work offers promising application in the areas of flexible and wearable electronics.

Archives of microbiology: screening of pectinase-producing bacteria from citrus peel and characterization of a recombinant pectate lyase with applied potential.

Pectinase is widely used in numerous industrial fields, including the food, wine, and paper industries. In this work, seven bacteria were isolated from orange peel and their pectinase production activity was assayed. One bacterium (OR-B2) identified as a Bacillus sp. showed the highest enzyme activity towards others. A gene encoding a pectate lyase designed as PelB-B2 in this work was amplified and heterogeneous expressed in E.coli. PelB-B2 was defined as a member of the PelB pectate lyase family after phylogenic tree analysis. 3D model of PelB-B2 was constructed by SWISS-MODEL and PelB-B2 showed conserved para-β structure. After inducing culture and purified by Ni-affinity chromatography, the properties of the purified PelB-B2 were assayed. Optimal pH and temperature for PelB-B2 was pH 8.0 and 50 °C, respectively. PelB-B2 showed excellent pH stability and thermostability. It was stable within pH range 3.0-11.0 and retained more than 51% activity after incubation at 40 °C, 50 °C, or 60 °C for 1 h. Furthermore, we determined that PelB-B2 was a Ca2+-dependent pectinase and the pectin extracted from citrus was the benefit substrate for PelB-B2. The Km and Vmax of PelB-B2 were 1.64 g/L and 232.56 mol/(L min), respectively. The OR-B2 can be a new resource for pectinase production and the PelB-B2 has potential for industrial application. 7 bacteria were isolated from orange peel, namely OR-B1 to OR-B7 and their pectinase activities were assayed. One pectate lyase belongs to PelB family was cloned from OR-B2 and heterogeneous expressed in E. coli. Purified PelB-B2 was further studied with its properties. Effects of pH, temperature, chemicals, substrate on the enzyme activity were assayed and the enzyme kinetic was also measured.

Preparation and Characterization of Ethylenediamine-Polyurea Microcapsule Epoxy Self-Healing Coating.

Polyurea microcapsules with Ethylenediamine (EDA) as the core material were synthesized. A set of characterization methods, including optical and scanning electron microscopy (OM and SEM), the Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) were used to confirm the microcapsule morphology and chemical structures. The influence of emulsifier content and stirring rate on size and morphology of the microcapsules was investigated, and the self-healing performance of EDA-Polyurea microcapsule/epoxy coatings was evaluated by electrochemical impedance spectroscopy (EIS) measurements. The results showed that the microcapsules obtained had good spherical shape with a mean diameter of 0.54–0.70 μm. Compared with pure core material, the microcapsule showed excellent thermostability, and the content of core materials was up to 56.00 wt%. The epoxy coating with 5.0 wt% EDA-Polyurea microcapsules achieved average corrosion resistance efficiencies of 90.00%, significantly enhancing the capability of the scratched coating to resist external corrosion.

Enhanced sintering resistance of bimetal/SBA-15 catalysts with promising activity under a low temperature for CO methanation.

According to its thermodynamic equilibrium analysis and strong exothermic characteristics, the major challenge of syngas methanation is to develop a high-efficient low-temperature catalyst with superior sintering resistance. In this study, bimetal-based SBA-15 catalysts were prepared via a citric acid-assisted impregnation method and applied in CO methanation. The obtained catalysts were characterized via X-ray diffraction, N2 adsorption–desorption, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction and other techniques. Combining the structural characterization of the fresh and used catalyst, the function of the organic additive and metal promoters was revealed. The catalysts exhibited superior low-temperature activity and excellent sintering resistance owing to the electron migration from the additive metal to Ni, strong interaction between the metal and support and the confinement effect of the support. The catalyst with Mo as a promotor exhibited the best dispersion and the largest surface concentration of nickel, which resulted in its highest catalytic activity among the catalysts. The design and preparation of a highly effective catalyst can provide novel insight into the preparation of other catalysts.

Flexible ZnO/PANI/nonwoven nanocomposite based high-sensitive NH3 gas sensor via vapor phase polymerization method

A new synthetic method to flexible sensor towards NH3 with response magnitude as high as 4300% was based on vapor phase polymerization (VPP), where zinc oxide (ZnO) sheets were exposed to polyaniline (PANI) vapors on the flexible nonwoven fabric substrate. A possible brick wall masonry assembly structure of ZnO and PANI on the surface of nonwoven fabric was provided, which also possessed excellent mechanical flexibility and thermostability. The response value of flexible ZnO/PANI/nonwoven sensor increased from 5% to 4300% with the NH3 concentration varied over a wide range (0.5–10 ppm) at room temperature. Flexible and conductive ZnO/PANI/nonwoven composite material has good potential applications as NH3 gas sensor in environment monitoring components and wearable flexible devices.

Self-assembled composite nanoparticles based on zein as delivery vehicles of curcumin: role of chondroitin sulfate.

Composite nanoparticles composed of zein and chondroitin sulfate (CS) were self-assembled by the method of antisolvent precipitation to deliver curcumin (ZCCNPs). The structure of ZCCNPs changed from spheres to microaggregates with the increase of CS, involving hydrogen bonding and electrostatic and hydrophobic effects. The resistance of ZCCNPs to degeneration was improved by CS. The encapsulation efficiency of curcumin was enhanced by CS and showed the maximum (91.97%) when the mass ratio of zein-to-CS was 1 : 1 (ZCCNPs1:1). The crystallinity of curcumin changed to amorphous in ZCCNPs1:1. ZCCNPs1:1 exhibited great stability at pH 3.0-8.0, and it showed excellent thermostability at 35, 55, and 80 °C respectively for 120 min when the pH was 4.0 or 6.0. Meanwhile, it showed great storage stability at 4 and 22 °C respectively for 30 days. The retention rate of curcumin in ZCCNPs1:1 was higher than 65% within 8 days. The presence of CS improved the antiproliferative activity of curcumin-loaded zein nanoparticles (Cur-ZNPs) to HCT116 cells. ZCCNPs1:1 exhibited higher bioaccessibility (42.36%) than Cur-ZNPs. In addition, ZCCNPs1:1 exhibited excellent biocompatibility evaluated using in vitro cytotoxicity assay on NCM460 cells. The studies indicate that the delivery system fabricated in our work would be efficient for improving the application of hydrophobic nutrients in functional foods.