Properties of bacterial cellulose produced in grape medium by native isolate Gluconacetobacter sp

During the production of grape wine, the occurrence of thick leathery pellicle at the air‐liquid interface was found as a contaminant. The pellicle produced was investigated with a view to use as biodegradable polymer. The bacterium that is responsible for the pellicle production was isolated, characterized and identified as Gluconacetobacter sp. Pellicle was produced in pasteurized grape extract as well as in HS medium by the isolated organism in static conditions. The purified film was subjected for Fourier transform infrared spectroscopy and C¹³ solid NMR spectroscopy analysis, which confirmed the pellicle to be a cellulosic material. Scanning Electron Micrograph showed ultra fine network structure along with cells. The films were tested for its physicomechanical characters, barrier and thermal properties. The films of 25‐μ thickness showed very high tensile strength (41.158 MPa) and elongation of 0.987 mm. The thermal properties of the films were characterized by Differential scanning calorimetry and Thermo gravimetric analysis. The melt peak temperature was found to be 111.65°C. The percentage of weight loss was found to be 20% at 327.86°C. Barrier properties (oxygen transmission rate and water vapor transmission rate), indicated a high oxygen barrier but low water barrier. This is the first report on the barrier properties of bacterial cellulose from Gluconacetobacter sp. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Physicochemical properties of bacterial cellulose obtained from different Kombucha fermentation conditions

The production of bacterial cellulose has been limited due to its high cost and low productivity. Alternative low-cost sources of this biopolymer of high purity and biocompatibility are needed in order to benefit from its enormous potential. Kombucha tea is a trend functional beverage whose production is growing exponentially worldwide, and the bacteria present in this fermented beverage belonging to the genus Komagataeibacter are capable of producing a crystalline biofilm with interesting properties. Obtaining bacterial cellulose from Kombucha tea has already been studied, however several fermentation conditions are being optimized in order to scale-up its production. In this study, we characterized the bacterial cellulose produced from three different Kombucha fermentation conditions. The scanning electron microscopy images revealed the crystalline structure of the biofilms. The energy-dispersive x-ray analysis exhibited the chemical composition of the crystals. The thermogravimetric analysis showed a rate of degradation between 490 and 560°C and the differential scanning calorimetry confirmed the presence of crystalline and amorphous regions in the bacterial cellulose samples. The results suggested that crystalline cellulose could be obtained by varying the fermentation conditions of Kombucha tea.     

Enzymatic saccharification of dissolution pretreated waste cellulosic fabrics for bacterial cellulose production by Gluconacetobacter xylinus

BACKGROUND: Waste textiles, such as dyed cellulosic and/or polyester blended fabrics have the potential to serve as an alternative feedstock for the production of biological products via microbial fermentation. Dissolution pretreatment was employed to enhance the enzymatic saccharification of dyed and synthetic fiber blended cellulosic fabrics. The fermentable reducing sugars obtained from waste cellulosic fabrics were used to culture Gluconobacter xylinus for value‐added bacterial cellulose (BC) production. RESULTS: Concentrated phosphoric acid was the ultimate cellulose solvent for dissolution pretreatment since 5% w/w cellulosic fabric can be completed dissolved at 50 °C. After regeneration in water, the cellulosic precipitate was subjected to cellulase hydrolysis, resulting in at least 4‐fold enhancement of saccharification rate and reducing sugars yield. The colored saccharification products can be utilized by G. xylinus to produce BC, approximately 1.8 g L^?1 BC pellicle was obtained after 7 days static cultivation. CONCLUSION: Dyed and blended waste fabric can be pretreated effectively by dissolution to produce fermentable sugars by cellulase hydrolysis. Dissolution pretreatment can expose the dyed or polyester fiber covered digestible cellulosic fibers to cellulase and leads to a significant enhancement of saccharification yield. The colored saccharification products have no significant inhibiting effect on the fermentation activity of G. xylinus for BC production. Copyright © 2010 Society of Chemical Industry     

Preparation and properties of bacterial cellulose/graphene oxide composite films using dyeing method

In this study, bacterial cellulose (BC) hydrogels were cultured from a kombucha SCOBY starter. The scanning electron microscopy (SEM) results indicated that the dried BC exhibited an interpenetrating fibrous mat. The BC films harvested for 5, 10, and 15 days were 15–19, 14.4–24, and 30–31 μm thick, respectively. Then, BC/graphene oxide (GO) composite films were prepared via the exhaust dyeing method. GO sheets penetrated the BC matrix, resulting in the formation of a BC/GO composite, as revealed by the SEM analysis results. The mechanical properties of the composite films were investigated. Compared with virgin BC, the tensile strength of the composite films was higher, while the %E at break was lower, resulting in a significant increase in the Young's modulus. The X-ray diffraction results indicated that an increase in the dyeing time (0.5–2 h) gradually induced cellulose crystalline conformation, which in turn affected the swelling ability, mechanical properties, and electrical properties of the BC/GO composite films. After the reduction of GO to reduced GO (rGO), flexible conductive BC/rGO films were obtained, as confirmed by their resistivity values. Thus, flexible conductive composite films with excellent mechanical properties were successfully fabricated.     

添加海藻酸钠对椰子水体系合成细菌纤维素的影响

以椰子水为培养体系,向培养基中添加海藻酸钠,利用木醋杆菌(Ax.)静态培养合成细菌纤维素(BC)。研究发现,培养体系中添加少量海藻酸钠,能显著提高产物的产量,添加量为4 g/L时,产量最大(8.35 g/L),是其他条件相同情况下不添加海藻酸钠时BC产量(3.47 g/L)的2.4倍。采用FTIR、XRD、TGA、SEM对产物进行了表征;并测试了产物的含水率及力学性能。结果表明,海藻酸钠的添加,对产物化学结构无改变,但一定程度降低了细菌纤维素结晶指数;降低了产物含水率和产物干膜的拉伸强度及断裂伸长率。     

细菌纤维素/碳纳米管/MnO2复合超级电容器电极

基于细菌纤维素(BC)的三维多孔及柔性支架结构和碳纳米管(MWCNT)的优良导电性,构筑起BC/MWCNT自支撑导电基底。其中,二者通过氢键紧密结合,协同赋予复合基底优良的电导率和机械性能。然后将二氧化锰(MnO₂)电沉积在该基底上,构建了一种新型的BC/MWCNT/MnO₂薄膜电极。BC/MWCNT复合膜的多孔结构、电解质吸收特性及蜂窝状活性MnO₂纳米片的桥连结构,赋予其出色的电化学性能(在1 mA cm_-2^{的电流密度下},其面积比电容和质量比电容分别达到1.17 F cm_-2^和200 F g_-1⁾和显著的循环稳定性(在20 mA cm_-2^{的电流密度下进行}10000次循环后,其比电容保留率稳定在96%)。这种无粘合剂的薄膜电极制备简便且成本低廉,在开发柔性储能器件方面具有巨大潜力。关键词：细菌纤维素(BC);碳纳米管(MWCNT);二氧化锰(MnO₂);膜电极;电化学性能中图分类号：TQ630 文献标识码： A 文章编号：1003-5214 (2020) 01-0000-00     

Viscoelastic properties of cellulose derivatives: 2. Effect of diethylphthalate on the dynamic mechanical relaxations of cellulose acetate

The dynamic mechanical spectra of cellulose acetate (CA) with various amounts of diethylphthalate (DEP), from 3 to 50 wt%, have been obtained over a range of temperatures (−130°C to 240°C) and frequencies (0.1 to 30 Hz). The effect of DEP addition on the main () relaxation is to shift the dispersion and corresponding modulus drop to lower temperatures. The depression of the transition temperature is smaller than commonly found for polymer-diluent mixtures. The influence of DEP on the secondary β and γ relaxations is quite different: while the low-temperature γ dispersion is progressively depressed by DEP addition, the intensity of the β relaxation increases strongly at DEP contents higher than 15%. The dynamic modulus increases with γ peak depression and shows a more intense drop with the strengthening of the β relaxation. The activation energy of the β dispersion remains fairly constant up to 15% DEP content, then increases to approach, at 50% DEP, the ΔH value of the relaxation of the pure diluent. At high DEP contents, active participation of the diluent molecules in the motion responsible for the β relaxation is suggested.     

Green esterification: A new approach to improve thermal and mechanical properties of poly(lactic acid) composites reinforced by cellulose nanocrystals

Cellulose nanocrystal (CNCs)‐reinforced poly(lactic acid) (PLA) nanocomposites were prepared using twin screw extrusion followed by injection molding. Masterbatch approach was used to achieve more efficient dispersion of CNCs in PLA matrix. Modified CNCs (b‐CNCs) were prepared using benzoic acid as a nontoxic material through a green esterification method in a solvent‐free technique. Transmission electron microscopy images did not exhibit significant differences in the structure of b‐CNCs as compared with unmodified CNCs. However, a reduction of 6.6–15.5% in the aspect ratio of b‐CNCs was observed. The fracture surface of PLA‐b‐CNCs nanocomposites exhibited rough and irregular pattern which confirmed the need of more energy for fracture. Pristine CNCs showed a decrease in the thermal stability of nanocomposites, however, b‐CNCs nanocomposites exhibited higher thermal stability than pure PLA. The average storage modulus was improved by 38 and 48% by addition of CNCs and b‐CNCs in PLA, respectively. The incorporation of b‐CNCs increased Young's modulus, ultimate tensile stress, elongation at break, and impact strength by 27.02, 10.90, 4.20, and 32.77%, respectively, however, CNCs nanocomposites exhibited a slight decrease in ultimate strength and elongation at break. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46468.     

MVR+A~2/O+MBR法处理毒死蜱环化废水

以三维丰海公司毒死蜱环化废水的深度处理工程为实例,介绍了该工艺的特点、设计参数、处理效果及运行成本。处理后最终出水水质良好,COD、BOD5、NH3-N、SS的去除率分别高达99.7%、99.7%、99.3%、99.0%,总盐分也由30 000 mg/L降至357 mg/L,出水指标优于国家《污水综合排放标准》(GB 8978—1996)一级标准,可直接回用于循环冷却水的补充用水。     

Production of a halotolerant lipase from Halomonas sp. strain C2SS100: Optimization by response-surface methodology and application in detergent formulations

The aim of this work was to optimize the production of a new lipase by a halotolerant bacterial strain Halomonas sp. C2SS100, by means of the response-surface methodology (RSM). The process parameters having the most significant effect on lipase production were identified using the Plackett–Burman screening design-of-experiments. Then, Box–Behnken design was applied to optimize lipase activity and the quadratic regression model of the lipase production was built. Indeed, the lipase yield was increased, and the value obtained experimentally (39 ± 2 U/ml) was very close to the rate predicted by the model (40.3 U/ml). Likewise, optimization of parameters by RSM resulted in 2.78-fold increase in lipase activity. These findings provide the first report on lipase production and optimization by a halotolerant bacterial strain belonging to Halomonas genus. Afterward, the biochemical properties of the produced lipase were studied for apply in oil stains removal. The crude lipase showed a maximum activity at 60°C and at pH ranging from 7 to 10. It displayed an important stability at high temperature, pH, and NaCl. Interestingly, this bacterial lipase exhibited a prominent stability toward some commercial solid and liquid detergents after 30 min of incubation at 50°C. The capability of the crude lipase to eliminate stain was ascertained on polycotton fabric pieces stained with lubricating oil. Whether with the addition of hot water alone or of a commercially available detergent, lipase is able to considerably boost the elimination of oil stains. The actual findings highlight the capacity of Halomonas sp. lipase for energy-efficient biocatalytic application.     

A novel compound, 12,13,17-trihydroxy-9(Z)-Octadecenoic acid,from linoleic acid by a new microbial isolateClavibacter sp. ALA2

A novel compound, 12,13,17-trihydroxy-9(Z)-octadecenoic acid (THOA), was produced from linoleic acid by microbial transformation at 25% yield. The newly isolated microbial strain that catalyzed this transformation was identified asClavibacter sp. ALA2. The product was purified by high-pressure liquid chromatography, and its structure was determined by¹H and¹³C nuclear magnetic resonance, Fourier transform infrared, and mass spectroscopy. Maximum production of THOA was reached after 85 h of reaction. THOA was not further metabolized by strain ALA2. This is the first report on 12,13,17-trihydroxy unsaturated fatty acid and its production by microbial transformation.     

Wood flour: A new filler for the rubber processing industry. III. Cure characteristics and mechanical properties of nitrile butadiene rubber compounds filled by wood flour in the presence of phenol‐formaldehyde resin

Nonmodified and corona‐activated conifer wood flour was evaluated as filler to nitrile butadiene rubber (NBR) compounds containing different amounts of phenol‐formaldehyde resin (PFAR) by studying the cure characteristics and the mechanical properties of the filled compounds. It was found that the PFAR affects considerably the cure characteristics and the mechanical properties of the wood flour–filled NBR compounds due to a presumable action as an interface interactions modifier. Acting as an antiaging agent it improves also their thermal‐oxidative stability. The optimal amount of PFAR regarding the cure characteristics and mechanical parameters is of 15 phr/100 phr wood flour. The addition of PFAR just before the wood flour is preferable because of both its better homogenization in the rubber matrix and its lower adsorption by the wood flour, leading to an improvement of the mechanical properties of the wood flour–filled NBR compounds. The replacement of nonmodified wood flour by corona‐activated wood flour leads to additional increase of the mechanical parameters without significant affect of the optimum cure time, aging resistance, and water adsorption. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 95–101, 2004     

Mechanical and dielectric properties of porous magnesium aluminate (MgAl2O4) spinel ceramics fabricated by direct foaming-gelcasting

Porous ceramic materials have been broadly applied in various fields due to their multifunctional properties. Optimization of their microstructural characteristics, such as pore morphology, total porosity, and pore size distribution, which determine various properties of the final products, is crucial to improve their performances and thus extend their applications. In this study, single-phase porous MgAl₂O₄ materials were fabricated by direct foaming–gelcasting. With an increase in the foam volume from 260 to 350 mL, the total porosity and pore size of the porous ceramic increased, and its microstructure varied from mostly closed cells to open cells containing interconnected large pores (40–155 μm) and small circular windows (10–40 μm) in the ceramic skeleton. The total porosity could be tailored from 84.91% to 76.08% by modulating the sintering temperature and foam volume and the corresponding compressive strengths were in the range of 2.8–15.0 MPa. The compressive strength exhibited a power-law relationship with the relative density with indices of approximately 3.409 and 3.439, respectively. Porous MgAl₂O₄ ceramics exhibited low dielectric constants in the range of 1.618–1.910 at room temperature, which are well matched with theoretical calculations on account of a modified Bruggeman model. The porous MgAl₂O₄ ceramics with good mechanical and dielectric properties controlled easily by various sintering temperatures and foam volumes are promising for practical applications.