对萘磺酸钠修饰的石墨烯基纳米银复合抗菌材料的制备及性能评价

制备采用1-萘磺酸钠修饰的石墨烯基纳米银复合材料,并对其性能进行评价。首先制备了石墨烯基纳米银复合材料,采用1-萘磺酸钠修饰,记为AgNP/rGO-NA,然后通过与聚乙烯吡咯烷酮做保护剂的纳米银（PVP/AgNP）的比较,分析其稳定性,抗菌活性,细胞毒性。研究发现,纳米银AgNP在制备的复合材料表面的分布相对均匀,AgNP的质量分数为4.3%,粒径为5~15nm,Zeta电位为-42.5 mV;在无光或光照强度为3000 Lx（勒克斯）的低温光照仪环境下储存10 d,PVP/AgNP聚集作用较为明显,而AgNP/rGO-NA则分散性良好,聚集作用不明显;AgNP/rGO-NA具有更加良好的抗菌活性,生物相容性和相对较低的生物毒性。试验表明经过1-萘磺酸钠修饰的石墨烯基纳米银复合材料质量可靠,性能良好,具有广阔的应用前景。     

纳米银胶/壳聚糖复合抗菌剂的制备及其在洗涤产品中抗菌性能

本文研究了纳米银胶/壳聚糖抗菌剂的制备及其形貌的表征分析,以大肠杆菌为代表菌株,研究了复合抗菌剂在洗涤产品中的抗菌效率及抗菌的稳定性,结果说明复合抗菌剂在洗涤产品中添加1.0%时,其抗菌效率达99%,经180 d长期分析,其抗菌活性仍保持95%左右。此外,复合抗菌剂对不同菌株的抗菌性能也均较强。     

黄原酸酯法接枝1.丙烯酰胺和蔗渣纤维浆泊接枝共聚的研究

采用纤维素黄原酸酯——过氧化氢构成氧化还原体系,把丙烯酰胺接枝到蔗渣纤维浆泊上。探讨了引发剂用量、初始pH值、单体比、反应温度、反应时间诸因素对接枝共聚反应的影响。     

Experimental evolution of Pseudomonas putida under silver ion versus nanoparticle stress

Whether the antibacterial properties of silver nanoparticles (AgNPs) are simply due to the release of silver ions (Ag⁺) or, additionally, nanoparticle-specific effects, is not clear. We used experimental evolution of the model environmental bacterium Pseudomonas putida to ask whether bacteria respond differently to Ag⁺ or AgNP treatment. We pre-evolved five cultures of strain KT2440 for 70 days without Ag to reduce confounding adaptations before dividing the fittest pre-evolved culture into five cultures each, evolving in the presence of low concentrations of Ag⁺, well-defined AgNPs or Ag-free controls for a further 75 days. The mutations in the Ag⁺ or AgNP evolved populations displayed different patterns that were statistically significant. The non-synonymous mutations in AgNP-treated populations were mostly associated with cell surface proteins, including cytoskeletal membrane protein (FtsZ), membrane sensor and regulator (EnvZ and GacS) and periplasmic protein (PP_2758). In contrast, Ag⁺ treatment was selected for mutations linked to cytoplasmic proteins, including metal ion transporter (TauB) and those with metal-binding domains (ThiL and PP_2397). These results suggest the existence of AgNP-specific effects, either caused by sustained delivery of Ag⁺ from AgNP dissolution, more proximate delivery from cell-surface bound AgNPs, or by direct AgNP action on the cell's outer membrane.     

Microbial degradation of acrylamide monomer

Acrylamide, a neurotoxic monomer with extensive industrial applications was found to be degraded by the microorganisms present in a tropical garden soil. A bacterium capable of degrading acrylamide was isolated from this soil by enrichment. It was found to be aerobic, gram-negative, motile, short rod and identified as Pseudomonas sp. The bacterium degraded high concentrations of acrylamide (4 g/l) to acrylic acid and ammonia which were utilized as sole carbon and nitrogen source for growth. An amidase was involved in the hydrolysis of acrylamide, which could act on other short chain amides like formamide and acetamide but not on acrylamide analogues: methacrylamide and N,N-methylene bis-acrylamide. The enzyme was sensitive to catabolite repression by succinate both in presence as well as absence of nitrogen source.Abbreviations Acrylamide (ACR) High Performance Liquid Chromatography (HPLC)     

Characterisation of silver nanoparticles synthesised by Bacillus thuringiensis as a nanobiopesticide for insect pest control

Nanotechnology has become one of the most promising new approaches for pest control in recent years. In this research, biocompatible silver nanoparticles (Btk-AgNPs) were synthesised by using the entomopathogenic bacterium, Bacillus thuringiensis kurstaki (Btk) as a low-cost and eco-friendly production system. The AgNP samples exhibited a brownish-yellow colour that is characteristic for silver nanoparticles synthesis. Btk-synthesised AgNPs were produced using both the supernatant and pellet of Bt culture at various concentrations and AgNP particles were characterised by UV-Vis spectrophotometer and Dynamic Light Scattering (DLS). The variation of hydrodynamic diameter (D_h) and UV-Vis spectra of silver particles produced by various concentration of culture showed that production of AgNPs was maximised when using 20% for either supernatant or pellet treatments of Bt of culture and the size of particles was around 85?nm for both. The insecticidal efficacy of Btk-synthesised AgNPs against larvae of the cabbage looper, Trichoplusia ni (Hübner) and black cutworm, Agrotis ipsilon (Hufnagel) was tested. Results demonstrated that the treatments of either Btk-synthesised AgNP(s) made with Bt supernatant or Btk-synthesised AgNP(p) using Bt pellet were found to be significantly more virulent toward larvae of T. ni than to A. ipsilon.     

Chemical and gamma-ray-modified bagasse as substrates for bioproduction of cellulases and protein

Production of enzymes in the cellulolytic complex was determined in culture filtrates of six fungal isolates grown on chemically treated or gamma-irradiated bagasse. The enzymatic activities of the filtrates were determined by measurement of glucose release from cotton, filter paper, carboxymethylcellulose, cellobiose, and cellobiose octaacetate. Cultures grown on base-treated and gamma-irradiated plus acid-treated bagasse provided culture filtrates with the highest enzymatic activities whereas alpha-cellulose, untreated, and acid-treated bagasse were the poorest substrates for enzyme production. Filtrates of Trichoderma reesei QM 9414 yielded the highest cellulolytic activity in all test media. The largest accumulation of fungal-derived, extracellular protein was observed in media containing gamma-irradiated bagasse as the carbon substrate.     

Study on the Effect of Poly(Styrene 4-Sulfonic Acid-co-Maleic Acid) Toward Metallization and Plasmonic Tuning of Silver Nanoparticle Thin Films

Thin films with tunable optical properties from yellow to metallic were prepared from a monolayer coating of silver nanoparticles (AgNP) onto a polyelectrolyte multilayer (PEM) thin film. The AgNP were synthesized using various concentrations of stabilizing polyelectrolytes leading to a competitive adsorption concept in which AgNP compete with excess polyelectrolytes to coat the cationic PEM top layer. The AgNP were synthesized by chemical reduction of Ag salts using poly(styrene 4-sulfonic acid-co-maleic acid) (PSS-co-MA) as stabilizing agent to produce nanoparticles coated with both a strong acid (sulfonic) and a weak acid (carboxylic) moiety. Although all the nanoparticle solutions displayed a characteristic bright yellow due to the localized surface plasmon band around 420 nm, the monolayer films of nanoparticles obtained after dipping displayed striking different optical properties. When using a high PSS-co-MA content in the solution, a pale-yellow film was obtained which color shifted to orange and metallic when the capping concentration was decreased from 0.25 to 0.001 mM. The optical properties of the AgNP film could be further changed by galvanic replacement of the Ag with gold ions to produce a gold monolayer. These results are interesting to produce surface with tunable catalytic properties, tunable optical properties, or to be used as primer for the metallization of polymeric surfaces.

     

Use of sugarcane bagasse and grass hydrolysates as carbon sources for xylanase production by Bacillus circulans D1 in submerged fermentation

The use of sugarcane bagasse and grass as low cost raw material for xylanase production by Bacillus circulans D1 in submerged fermentation was investigated. The microorganism was cultivated in a mineral medium containing hydrolysate of bagasse or grass as carbon source. High production of enzyme was obtained during growth in media with bagasse hydrolysates (8.4 U/mL) and in media with grass hydrolysates (7.5 U/mL). Xylanase production in media with hydrolysates was very close to that obtained in xylan containing media (7.0 U/mL) and this fact confirm the feasibility of using this agro-industrial byproducts by B. circulans D1 as an alternative to save costs on the enzyme production process.     

Influence of the application of sugarcane bagasse on lindane (gamma-HCH) mobility through soil column: implication for biotreatment

In the present study we employed sugarcane bagasse for biotreatment of soil containing 50mgkg(-1) of lindane. Garden soil were treated with lindane and amended with varying concentrations of sugarcane bagasse (10%, 20%, 30%, 40% and 50%; w/w). Data on dissipation and degradation of lindane in soil columns (0-15, 15-30cm) were studied at six consecutive samplings (0, 3, 7, 45 and 60 days). Treatment with 50% sugarcane bagasse resulted in >53% degradation of lindane in upper soil column with minimal leaching to lower soil column (0.002%) while highest leaching of lindane from upper soil column to lower soil column was occurred in garden soil (35.8%). Similarly, a substantial microbial biomass input has detected in amended soil than garden soil. Our results provide evidence that sugarcane bagasse can accelerate lindane degradation by enhanced microbial activity and prevent pesticide mobility through soil column by adsorption. Sugarcane bagasse could be useful as cheaper, easy available alternative for the biotreatment of lindane impacted soil.     

The effect of fire retardants on combustion and pyrolysis of sugar-cane bagasse

Experiments were conducted by thermal gravimetric analysis (TGA) and cone calorimetry to measure the affect of three fire retardants (ammonium sulphate, boric acid and borax) on the mass-loss rate and combustion characteristics of sugar-cane bagasse. Compared with untreated bagasse, bagasse impregnated with aqueous solutions of 0.1-0.5 M fire retardants exhibited an increase in char mass production from 16% up to 41% when pyrolysed and up to a 41% reduction in total heat release (THR) during combustion. Char mass production was only a weak function of additive concentration over the range of concentrations (0.1-0.5 M) used. Combining the additives did not show any synergistic effects for char production or heat release rate (HRR). Treatment of bagasse by these chemicals could be useful to enhance biochar yields in pyrolysis processes or to reduce flammability risk in composites containing bagasse.     

Appearance and phosphorylation of the 210 kDalton neurofilament protein in newborn rat brain,spinal cord,and sciatic nerve

The appearance and in vivo phosphorylation of the 210 kDalton (kD) neurofilament protein (NF210K) in newborn rat brain, spinal cord, and sciatic nerve were invetigated. Electron microscopic examination of neurofilaments isolated from newborn rat brain and spinal cord demonstrated morphologically distinct filaments which contained cross-bridging side arms. Neurofilament proteins, phosphorylated in vivo, were separated by sodium dodecyl sulfate slab gel electrophoresis and were transferred from acrylamide gels to nitrocellulose sheets. The nitrocellulose sheets were treated with antiserum to the 70 kD, 145 kD and 210 kD neurofilament proteins by the immunoblot technique. The three neurofilament proteins were found to be present in newborn brain, spinal cord and sciatic nerve. The presence of NF210K in newborn rat brain was further confirmed by 2-dimensional gel electrophoresis followed by indentification of this protein by the immunoblot technique. Exposure of the immunostained nitrocellulose sheets to x-ray film revealed that the NF210K, NF145K, and NF70K proteins were phosphorylated in filaments prepared from newborn rat central and peripheral nervous systems. These results suggest that the synthesis and posttranslational modification of the neurofilament proteins may be synchronized or developmentally regulated. It is feasible that phosphorylation of the NF210K subunit may be a prerequisite for the formation of neurofilament cross-bridging elements which are necessary for radial growth of axons.     

A simple method for the preparation of polyacrylamide gels containing thioglycoside ligands.

A simple method was developed for the preparation of acrylamide derivatives containing thioglycosides. The synthetic scheme involves the preparation of an O-acetylated 1-thiosugar via a pseudothiourea derivative, the controlled addition of the thiosugar to N,N′-bismethyleneacrylamide to form a monoaddition product in which one of the acrylamide groups remains unchanged, and finally de-O-acetylation. Similar reaction schemes using bisacrylamido derivatives of 1,2-diaminoethane and 1,6-diaminohexane lead to analogous compounds with longer aglycon chain lengths. The thioglycoside derivatives of acrylamide thus prepared could be copolymerized with acrylamide to form polymers or gels containing thioglycosides as ligands. These gels were successfully used as affinity materials for the purification of peanut lectin and in cell-adhesion studies.     

Two-dimensional crystals formed from photosynthetic reaction centers

Photosynthetic reaction centers from the bacterium Rhodopseudomonas viridis were prepared after detergent solubilization of photosynthetic membranes. The purified reaction centers, in agreement with reports from other laboratories, contain four distinct polypeptides ranging in molecular weight from 28,000 to 41,000. When the detergent was gradually removed by dialysis under appropriate conditions, large two- dimensional sheets of reaction centers were formed, suitable for analysis by electron microscopy. The crystals were rectangular, and the dimensions of a single unit cell were 121 X 129 A. Each unit cell contained four distinct subunits, each with approximate dimensions of 45 X 60 A. The thickness of the sheet was 60 A. Preliminary studies of the sheets with negative staining indicated that the sheets show a high degree of order: as many as six orders are visible in transforms of the images. Because of the fact that in R. viridis the native membrane from which these reaction centers were purified also displays a crystal-like structure, comparative studies between a membrane and one of its components, each analyzed by Fourier techniques, are now possible.     

Proteins and glycoproteins of the erythrocyte membrane

Erythrocyte membranes from several species were prepared by three different methods of hypotonic hemolysis and examined for variations in protein and glycoprotein content by acrylamide gel electrophoresis in sodium dodecyl sulfate. Significant variations were noted in morphology of the membranes prepared by the different methods without attendant variations in protein patterns of the major membrane proteins for most cases observed, which show a similar pattern of nine common bands for all of the species observed. The significant difference in protein pattern which was noted was attributed to proteolytic digestion of membranes which were fragmented during preparation. Failure to remove white blood cells from membrane preparations was shown to be a significant source of the problem with proteolytic digestion. Glycoproteins were analyzed by acrylamide gel electrophoresis or by column chromatography. Each species appears to have a different major glycoprotein (or group of closely related glycoproteins). Molecular weights of glycoproteins calculated from acrylamide gel electrophoresis were found to vary with the percentage of acrylamide in the gel, indicating that these proteins do not behave in a normal fashion in this electrophoresis system. The molecular weight calculated from gel filtration data for the human membrane glycoproteins (26,000) was quite disparate from those calculated from gel electrophoresis (88,000 to 62,000 in 5 to 10% gels).     

Performance of improved bacterial cellulose application in the production of functional paper

Aim: The purpose of this work was to study the feasibility of producing economic flame retardant bacterial cellulose (BC) and evaluating its behaviour in paper production. Methods and Results: This type of BC was prepared by Gluconacetobacter subsp. xylinus and substituting the glucose in the cultivation medium by glucose phosphate as a carbon source; as well as using corn steep liquor as a nitrogen source. The investigated processing technique did not dispose any toxic chemicals that pollute the surroundings or cause unacceptable effluents, making the process environmentally safe. The fire retardant behaviour of the investigated BC has been studied by non‐isothermal thermogravimetric analysis (TGA & DTGA). The activation energy of each degradation stage and the order of degradation were estimated using the Coats–Redfern equation and the least square method. Strength, optical properties, and thermogravimetric analysis of BC‐phosphate added paper sheets were also tested. Conclusions: The study confirmed that the use of glucose phosphate along with glucose was significant in the high yield production of phosphate containing bacterial cellulose (PCBC1); more so than the use of glucose phosphate alone (PCBC2). Incorporating 5% of the PCBC with wood pulp during paper sheet formation was found to significantly improve kaolin retention, strength, and fire resistance properties as compared to paper sheets produced from incorporating bacterial cellulose (BC). Significance and Impact of the Study: This modified BC is a valuable product for the preparation of specialized paper, in addition to its function as a fillers aid.     

Effect of pulping variables with dimethyl formamide on the characteristics of bagasse-fiber

Organosolv pulping of bagasse was conducted following a central composite design using a two-level factorial plan involving three pulping variables (temperature: 190-210 degrees C, time: 120-180 min, organic solvent ratio: 40-60% dimethyl formamide). Responses of pulp and handsheets properties to the process variables were analyzed using statistical software (MINITAB 14). Using values of the independent variables the variation ranges considered provided the following optimum values of the dependent variables: 82.7% (yield), 92.9 (kappa number), 1.403% (ash), 370 ml (freeness), 6290 m (breaking length), 9.4 (folding endurance), 5.955 mN m2 g(-1) (Tear index) and 2.811 kN g(-1) (Burst index) for pulps and handsheets. Results showed that acceptable physical and mechanical properties of pulps and papers similar the pulp used for bleaching could be achieved at 210 degrees C for 150 min and 50% DMF. These are the most suitable conditions for obtaining paper sheets with a high breaking length, tear and burst indices. Also bagasse could be pulped with ease to about 55.72% yield with kappa number approximately 35. The cooking temperature was a significant factor while the DMF ratio and cooking time were not as important in term of the properties of the resultant pulps and papers.     

Enzymic saccharification of sugarcane bagasse pretreated by autohydrolysis-steam explosion

Pretreatment of bagasse by autohydrolysis at 200 degrees C for 4 min and explosive defibration resulted in the solubilization of 90% of the hemicellulose (a heteroxylan) and in the production of a pulp that was highly susceptible to hydrolysis by cellulases from Trichoderma reesei C-30 and QM 9414, and by a comercial preparation, Meicelase. Saccharification yields of 50% resulted after 24 h at 50 degrees C (pH 5.0) in enzymic digests containing 10% (w/v) bagasse pulps and 20 filter paper cellulase units (FPU). Saccharifications could be increased to more than 80% at 24 h by the addition of exogenous beta-glucosidase from Aspergillus niger. The crystallinity of cellulose in bagasse remained unchanged following autohydrolysis-explosion and did not appear to hinder the rate or extent of hydrolysis of cellulose. Autohydrolysis-exploded pulps extracted with alkali or ethanol to remove lignin resulted in lowere conversions of cellulose (28-36% after 25 h) than unextracted pulps. Alkali extracted pulps arising from autohydrolysis times of more than 10 min at 200 degrees C were less susceptible to enzymic hydrolysis than unextracted pulps and alkali-extracted pulps arising from short autohydrolysis times (e.g., 2 min at 200 degrees C). Autohydrolysis-explosion was as effective a pretreatment method as 0.25M NaOH (70 degrees C/2 h) both yielded pulps that resulted in high cellulose conversions with T. reesei cellulase preparations and Meicelase. Supplementation of T. reesei C-30 cellulose preparations with A. niger beta-glucosidases was effective in promoting the conversion of cellulose into glucose. A ration of FPU to beta-glucosidase of 1:1.25 was the minimum requirement to achieve more than 80% conversion of cellulose into glucose within 24 h. Other factors which influenced the extent of saccharification of autohydrolysis-exploded bagasse pulps were the enzyme-substrate ratio, the substrate concentration, and the saccharification mode.     

Removal of color from biomethanated distillery spentwash by treatment with activated carbons

This work examined 19 carbon samples prepared by acid and thermal activation of various agro-residues viz. bagasse, bagasse flyash, sawdust, wood ash and rice husk ash for color removal from biomethanated distillery effluent. Phosphoric acid carbonized bagasse B (PH) showed the maximum color removal (50%). However, commercial activated carbons AC (ME) and AC (LB) showed better performance of over 80% color removal. Besides color removal, activated carbon treatment also showed reduction in chemical oxygen demand (COD), total organic carbon (TOC), phenol and total Kjeldahl nitrogen (TKN). The performance was related to the characteristics of the investigated samples. Further, adsorption isotherms for melanoidins, which is the primary coloring compound in distillery spentwash, followed the Langmuir isotherm implying monolayer adsorption.     

Xylanase production using inexpensive agricultural wastes and its partial characterization from a halophilic <Emphasis Type="Italic">Chromohalobacter</Emphasis> sp. TPSV 101

A halophilic and alkali-tolerant Chromohalobacter sp. TPSV 101 with an ability to produce extracellular halophilic, alkali-tolerant and moderately thermostable xylanase was isolated from solar salterns. Identification of the bacterium was done based upon biochemical tests and 16S rRNA sequence. The culture conditions for higher xylanase production were optimized with respect to NaCl, pH, temperature, substrates and metal ions and additives. Maximum xylanase production was achieved in the medium with 20% NaCl, pH-9.0 at 40°C supplemented with 1% (w/v) sugarcane bagasse and 0.5% feather hydrolysate as carbon and nitrogen sources. Sugarcane bagasse (250 U/ml) and wheat bran (190 U/ml) were the best inducer of xylanase when used as carbon source as compared to xylan (61 U/ml). The xylanase that was partially purified by protein concentrator had a molecular mass of 15 kDa approximately. The xylanase from Chromohalobacter sp. TPSV 101 was active at pH 9.0 and required 20% NaCl for optimal xylanolytic activity and was active over a broad range of temperature 40–80°C with 65°C as optimum. The early stage hydrolysis products of sugarcane bagasse were xylose and xylobiose, after longer periods of incubation only xylose was detected.