Microbial manganese oxide formation and interaction with toxic metal ions

Diverse bacteria and fungi oxidize Mn(II) enzymatically and produce insoluble Mn(III, IV) oxides, and these organisms are considered to be the primal agents for the occurrence of natural Mn oxide phases in most environments. Biogenic Mn oxides have a high sorption capacity for metal cations and an ability to oxidize numerous inorganic and organic compounds, owing to their structural and redox features. Thus, the microbial process is of significance in both biogeochemical and biotechnological contexts. In this article we summarize the enzymatic Mn(II) oxidation and interactions of biogenic Mn oxides with toxic metal and metalloid ions. Although Mn oxide formation by fungi has not been fully characterized yet, recent researches with ascomycetes emphasize the similarity between the bacterial and fungal Mn(II) oxidation with respect to the involved catalyst (i.e., multicopper oxidase-type enzymes) and the reaction product [i.e., layer-type Mn(IV) oxides]. Laboratory cultures of bacterial and fungal Mn oxidizers are expected to provide fundamental knowledge in their potential use for remediation of environments and effluents contaminated with toxic metal(loid) ions.     

Multifunctional nanocellulose/metal and metal oxide nanoparticle hybrid nanomaterials

Abstract

Nanocellulose materials are derived from cellulose, the most abundant biopolymer on the earth. Nanocellulose have been extensively used in the field of food packaging materials, wastewater treatment, drug delivery, tissue engineering, hydrogels, aerogels, sensors, pharmaceuticals, and electronic sectors due to their unique chemical structure and excellent mechanical properties. On the other hand, metal and metal oxide nanoparticles (NP) such as Ag NP, ZnO NP, CuO NP, and Fe₃O₄ NP have a variety of functional properties such as UV-barrier, antimicrobial, and magnetic properties. Recently, nanocelluloses materials have been used as a green template for producing metal or metal oxide nanoparticles. As a result, multifunctional nanocellulose/metal or metal oxide hybrid nanomaterials with high antibacterial properties, ultraviolet barrier properties, and mechanical properties were prepared. This review emphasized recent information on the synthesis, properties, and potential applications of multifunctional nanocellulose-based hybrid nanomaterials with metal or metal oxides such as Ag NP, ZnO NP, CuO NP, and Fe₃O₄ NP. The nanocellulose-based hybrid nanomaterials have huge potential applications in the area of food packaging, biopharmaceuticals, biomedical, and cosmetics.     

企业人力资源管理与吸引人才

1企业人力资源管理的特征 现阶段企业人力资源管理有如下特征： 第一,战略性.人力资源管理应当进入企业发展战略制订以及战略执行过程,人才管理的不完善将会导致企业的战略发展前景的缺失.     

The bacterial flora of non-carbonated, natural mineral water from the springs to reservoir and glass and plastic bottles

Quantitative and qualitative determinations of the bacterial flora of non-carbonated natural mineral water at the most important steps during bottling at a large water source yielded the following results: (i) Colony counts (on 1:10 diluted plate count agar, incubated at 20 degrees C for 14 days) for water of the five springs and the mixed water were less than 1 to 4 cfu ml-1. The Gram-negative bacterial flora (n = 50 isolates) showed a very different but constant spring specific species distributions with predominance of either eutrophic fluorescent pseudomonads, oligotrophic non-fluorescent pseudomonads or oligotrophic yellow bacteria. (ii) In the reservoir and immediately after bottling the counts were in the range of 10 cfu ml-1. But nearly 30% of the species of the spring water were no longer detectable and there was a significant increase of Gram-positive bacteria. (iii) After 1 week of storage at 20 degrees C colony counts of more than 10(5) cfu ml-1 were found in plastic bottles, but only about 10(4) cfu ml-1 in glass bottles. Besides, a very distinct change of the composition of the microflora occurred. In glass bottles slow-growing oligotrophic non-fluorescent pseudomonads, yellow bacteria and Acinetobacter predominated. In plastic bottles fast-growing eutrophic and mesotrophic fluorescent pseudomonads, Flexibacter and Acinetobacter were dominating. In mineral water, bottled into thoroughly cleaned glass bottles, colony counts of more than 10(5) cfu ml-1 were found within 4 days. In bottles, cleaned mechanically as usual, the increase was significantly slower with a maximum of only 5 x 10(3) cfu ml-1 after 8 days. The results of inoculation experiments in sterile filtered mineral and distilled water led to the suggestion that the difference between the two types of bottles is caused firstly by an inhibition of growth due to residues of cleaning detergents in the glass bottles. Growth promotion by dissolved organic substances in the plastic bottles only played a minor role. After repairing of the pump at a depth of 300 m in a warm mineral water spring, the colony counts at 20, 37 and 42 degrees C on 1:10 diluted and normal plate count agar increased beyond the limits required by the EC directive for mineral water stored a month. Then colony counts decreased slowly and reached the initial level after 1 year, except for the colony counts 1:10 diluted agar at 20 degrees C which stabilized at a relatively high number and a significant alteration of the microflora.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ceramide binding to African-American hair fibre correlates with resistance to hair breakage

Repetitive hair-relaxing treatments often applied to African–American hair weaken the hair structure. Therefore hair breakage is a common feature of African–American hair and an important cause of hair loss. Recently, by analysing the lipids extracted from human hair, a fraction of free-ceramide was isolated in which sphinganine was predominant. This study shows that this sphinganine-derived ceramide (i.e. C18-dhCer) binds to African–American hair and protects it from weakening caused by chemicals. To show this binding, we used two methods: radioactivity detection with a microimager^TM and secondary ion mass spectrometry.
We evaluated the benefits of C18-dhCer on African–American hair fibre, relaxed by guanidine hydroxide, using a new method called the Break'in Brush Technique (BBT^®). This method determines the hair breakage resistance during a brushing. Using this technique, we have shown less breakage when applying a shampoo with ceramide.
The present study opens new prospects for the development of products able to increase the protection, provide better care and meet the needs of African–American hair thanks to the effect of ceramide binding.     

Effects of aqueous polymeric surfactants on silicone-hydrogel soft- contact-lens wettability and bacterial adhesion of Pseudomonas aeruginosa

Prevention of Pseudomonas aeruginosa binding to soft-contact lenses (SCLs) may curtail sight-threatening microbial keratitis. Substrate surface wettability is known to modulate adhesion of P. aeruginosa. This study investigates the use of aqueous alkoxylate block co-polymer surfactants for enhanced wettability and antibacterial adhesion of SCLs under leaching conditions. Specifically, Pluronic^® F127 (PF) and three ethylene oxide-butylene oxide (EOBO) surfactants were studied with four commercially available silicone–hydrogel contact lenses: Pure Vision?, Acuvue Advance?, Acuvue Oasys? and O₂Optix?. Dilute aqueous PF and EOBO surfactants impregnated all four soft-contact lenses, as demonstrated by surface-tension decline for leached surfactant. For PF surfactant, significant surface-wettability improvement upon rinsing occurred only after overnight leaching. EOBO surfactant showed a similar pattern with O₂Optix? lenses. EOBO-pretreated Pure Vision? lenses, however, showed fast leaching and a significant change in surface energy towards improved wettability. Adhesion assays of P. aeruginosa displayed a small decrease in the binding rate of PAK bacteria for EOBO-pretreated Pure Vision? lenses, but not for EOBO-pretreated O₂Optix? lenses. P. aeruginosa strain-PAO1 bacteria adhesion to all lenses was independent of surface wettability. Despite the ability of polymeric surfactants to lower advancing contact angles under leaching conditions, increased lens wettability is not a universal panacea for antifouling of soft-contact lenses.     

Catalytic ozonation of propanal using wood fly ash and metal oxide nanoparticle impregnated carbon

Catalytic ozonation of propanal at ambient temperatures (23-25 degrees C) was investigated by varying propanal and ozone concentrations and catalyst type. The catalysts tested included wood fly ash (WFA), magnetically separated ash, synthetic hematite and magnetite, and metal oxide nanoparticle impregnated activated carbon and peanut hull char. A power law model independent of ozone concentration for WFA (r(w), moles g(-1) s(-1)) and magnetite (r(m)) were, respectively, r(w) = k'(w) C(R(0.89)) and r(m) = k'(m)C(R(1.55)), where kw, and k'(m) were 2.36 x 10(-6) g(-1) s(-1) (moles)(-0.11) (m3)(0.89) and 6.5 x 10(-4) g(-1) s(-1) (moles)(-0.55) (m3)(1.55), respectively (5-15 ppmv). Magnetite and hematite present in the WFA were theorized to be the primary active sites, since magnetically separated WFA had a significantly higher reaction rate (approximately 12x, mol m(-2) s(-1)) than that of WFA. X-ray diffraction analysis demonstrated a qualitative increase in magnetite and hematite in the magnetically separated ash, and synthetic magnetite and hematite had reaction rates >80x and 200x that of WFA or activated carbon (surface area basis). Supercritical deposition of hematite on/in peanut hull char successfully generated a porous, pelleted catalystfrom an agricultural residue capable of oxidizing propanal at rates 12x activated carbon and similar to commercially available catalysts (per mass basis). Water vapor significantly increased the propanal reaction rate when using wood fly ash and activated carbon.     

Non-covalent binding of proteins to polyphenols correlates with their amino acid sequence

The present paper describes the assessment of non-covalent binding (NCB) between milk proteins and polyphenols and its correlation with the physicochemical parameters of proteins. A method based on ultrafiltration and liquid chromatography-tandem mass spectrometry was used to analyse free and non-covalently bound polyphenols (ligands) in mixtures with major milk proteins. Binding strength values of individual polyphenols were normalised to those obtained with quercitrin (quercetin-3-O-rhamnoside), used as a reference compound. NCB data acquired by experiments at pH 6.6 without any preliminary protein denaturation were correlated with the physicochemical parameters of ligands and proteins. Unsupervised multivariate analysis revealed that NCB of proteins clustered according to their family (caseins separated from albumins). Based on this model, a predictive relationship was observed between protein-polyphenol binding strength and primary/secondary structure parameters of the proteins e.g. number of charges, proline residues and extended strand. These results confirm that, under the investigated experimental conditions, the NCB between polyphenols and protein mixtures can be predicted and optimised based on the molecular structures.     

Xylella genomics and bacterial pathogenicity to plants

Xylella fastidiosa, a pathogen of citrus, is the first plant pathogenic bacterium for which the complete genome sequence has been published. Inspection of the sequence reveals high relatedness to many genes of other pathogens, notably Xanthomonas campestris. Based on this, we suggest that Xylella possesses certain easily testable properties that contribute to pathogenicity. We also present some general considerations for deriving information on pathogenicity from bacterial genomics.     

Lactobacillus helveticus HY7801 ameliorates bacterial vaginosis by inhibiting biofilm formation and epithelial cell adhesion of Gardnerella vaginalis

Food Science and Biotechnology - Bacterial vaginosis (BV) is caused by a microbial imbalance in the vaginal ecosystem, which causes genital discomfort and a variety of potential complications in...     

Sorption of pyrene by regular and nanoscaled metal oxide particles: influence of adsorbed organic matter

Sorption of pyrene by regular and nanoscaled aluminum, zinc, and titanium oxides was examined. All oxides had low sorption for pyrene because of sorbed water molecules. Due to the larger surface area (SA) of nanoparticles, they had higher sorption for pyrene than the regular ones. Organic matter (OM) coating greatly enhanced pyrene sorption by all oxides, noting the importance of sorbed OM in sorption of hydrophobic organic compounds (HOCs). Due to higher sorption site density in the sorbed OM phase on the regular oxide surfaces, SA-normalized distribution coefficients (K(dSA)) of pyrene by OM-regular oxide complexes (6.0-40.6) were greater than the OM-coated oxide nanoparticles (0.7-12.5). Furthermore, the OM-regular oxide complexes had higher organic carbon content-normalized K(dSA) values of pyrene (48-17 300) than the OM-nanoscaled oxide complexes (15-1530). This variation may be due to different physical forms and fractionation of the loaded OM on regular and nanoscaled oxide particles.     

Search for a more adequate test to predict the long-term migration from the PVC gaskets of metal lids into oily foods in glass jars

As shown previously, the conventional testing procedure for simulating long-term migration from the gaskets of metal closures into oily foods does not adequately reflect reality. It appears to be impossible to accelerate migration to the extent that the situation at the end of the shelf life of a product can be anticipated in a few days or weeks. Therefore, we investigated whether long-term migration could be extrapolated from migration rates determined for new lids. Jars were kept in the normal upright position. Since heat treatment may have a strong temporary impact, migration during the initial heating for pasteurization or sterilization and storage at ambient temperature were determined using different lids. Commercial products were recalled from sales points throughout Europe to determine the real migration over extended periods of time and for jars with differing histories. This migration was compared with data from the short-term testing to investigate whether an empirical relationship could be derived. The results show that the short-term test enables the comparison of lids and plasticizers in the initial phase of migration, but that long-term extrapolation presupposes more complex kinetic modeling. The results also demonstrate that the legal relevance of “official” testing methods should be reconsidered to avoid conflict when food contact materials comply with migration limits in the test but not in actual application.     

大豆蛋白-氢氧化钙复合胶粘剂的研制

对大豆蛋白与氢氧化钙复合制备大豆胶粘剂进行了研究.考察了大豆蛋白与水质量比、大豆蛋白与氢氧化钙质量比、黏度改良剂乙醇与大豆蛋白质量比对复合胶粘剂耐水性的影响.通过正交实验优化出最佳配方为:大豆蛋白与水质量比1:8,大豆蛋白与氢氧化钙质量比3:1,乙醇与大豆蛋白质量比1:10.在此条件下制得的大豆胶粘剂施在胡桃木样品上,样品经3个浸泡干燥循环(48 h水浸泡和48 h空气干燥)后其剪切强度由未浸泡前的80 MPa降至72.8 MPa,仅下降了9%.结果表明,乙醇增黏后将大豆蛋白与氢氧化钙混合,可得到耐水性较好的复合胶粘剂.     

Ultrasound based glass fragments detection in glass containers filled with beverages using neural networks and short time Fourier transform

Glass fragments may accidentally make their ways to glass juice bottles, which has been a serious concern of beverage manufacturers. Using ultrasound to detect these fragments in the bottle poses a challenging task for signal processing and classification. When glass fragments settle down on the bottom or are sticked to the wall of a bottle, ultrasound signals returned from the fragments will superimpose themselves onto the echoes from the inner surface of the bottle. This superposition makes it impossible to distinguish the signals of bottles with fragment(s) from those without fragment(s) by commonly used methods such as time gating and spectrum analysis. A method is developed by combining radial basis function neural networks (RBF-NN) with short time Fourier transform (STFT) for ultrasound signal classification to detect glass fragments behind glass walls. The STFT algorithm was used to extract signal features while the RBF-NN was trained using the features to distinguish signals of bottles in presence from those in absence of glass fragments. Successful classification rate of 95% was achieved by this method.     

从德中金属制品贸易谈我国金属制品强国之路

研究德国金属制品业现状及进出口发展,分别介绍不锈钢丝、合金钢丝、碳素钢丝、钢丝绳进出口数量及其变化。研究德中金属制品贸易量和贸易额的现状和变化以及贸易地位。2013年德国从中国进口的金属制品数量和金额分别占其总进口金属制品的4.8%和5.2%;出口到中国的金属制品占其总出口量的2.2%,占总出口额的5%。比较德中金属制品贸易价格:2013年中国从德国进口金属制品的平均价格5 216美元/t,出口到德国的金属制品平均价格只有2 041美元/t,进口价格是出口价格的2.56倍。指出中国金属制品行业应进行产业结构调整和升级,企业应进行产学研结合、品牌质量建设、正确处理与原辅材料和设备企业的关系,共同建设金属制品强国。     

高黏附力双歧杆菌的筛选与鉴定

利用体外细胞培养法,从实验室现有的10株双歧杆菌中筛选具有较强粘附能力的菌株。采用革兰氏染色法和平板计数法,评价了这10株双歧杆菌对HT-29细胞的粘附性能,通过测定这10株双歧杆菌的16S rRNA基因序列(16S rDNA)进行分类学鉴定。结果显示,WBBI01,WBBI02,WBIN03,WBBI06具有极强的黏附力,其黏附指数分别达1.97×103,2.17×103,3.57×103,1.88×103。经16S rDNA测序鉴定WBBI01,WBIN03,WBBI06均与两歧双歧杆菌S17有极高的同源性,而WBBI02属于长双歧杆菌。结果表明,双歧杆菌黏附性能具有明显的种属特异性,不同种属双歧杆菌的粘附能力相差极大,以两歧双歧杆菌的黏附性能最强,婴儿长双歧杆菌为最弱。     

Permeability barrier of the gram-negative bacterial outer membrane with special reference to nisin

The effect of nisin pretreatment on organic acid-induced permeability increase in strains of Escherichia coli, Pseudomonas aeruginosa, P. marginalis, and Salmonella enterica sv. Typhimurium was investigated, using assays based on the uptake of a fluorescent dye 1-N-phenylnaphthylamine (NPN) and on the bacterial susceptibility to detergent-induced bacteriolysis. The outer membrane of bacteria which had been pretreated with nisin was shown to be less stable against 1 mM EDTA, as indicated by their significantly higher NPN uptake levels as compared to untreated bacteria. Upon challenge with a tenfold lower concentration of EDTA (0.1 mM) some nisin-treated strains (Typhimurium, P. marginalis) exhibited, however, NPN uptake levels which were lower than those seen in control bacteria, suggesting that nisin had stabilized their outer membrane. Nisin pretreatment also decreased the NPN uptake induced by citric or lactic acid or both in E. coli, P. marginalis, and Typhimurium, whereas in P. aeruginosa the pretreatment resulted in increased NPN uptake in response to citric and lactic acid. These results suggest that, with the exception of P. aeruginosa, nisin could protect bacteria from the outer membrane-disrupting effect caused by the acids. P. aeruginosa was, however, shown to be protected against bacteriolysis induced by the detergents sodium dodecylsulfate and Triton X-100. With a pair of isogenic mutants of Typhimurium differing in their cell surface charge it was shown that the NPN uptake response to 1 mM EDTA of the abnormally cationic strain was not significantly affected by nisin, whereas in the normal anionic strain nisin strongly strengthened the uptake. Our hypothesis based on these findings is that the normally anionic cell surface of Gram-negative bacteria has a tendency to bind the cationic nisin. The binding of nisin to the surface does not proceed to the cytoplasmic membrane, but in the outer membrane the bound nisin actually stabilizes its structure through electrostatic interactions. With the exception of EDTA, the organic acids at pH 4 did not cause leakage of cell contents from Typhimurium, indicating that these acids do not permeabilize the outer membrane to an extent required for cytoplasmic pore formation by nisin.     

Surface characteristics of Bacillus cereus and its adhesion to stainless steel

The ability of a Bacillus cereus strain, isolated from spoiled milk, to adhere to the surface of stainless steel chips was evaluated during its growth in diluted tryptic soy broth (DTSB). The number of cells that adhered to the surface increased markedly as the culture reached the end of the log phase and entered stationary phase, and continued to increase with further incubation. The surface properties of cells from the log, stationary, and late stationary phases were measured by hydrophobic interaction chromatography (HIC) and electrostatic interaction chromatography (ESIC). It was found that surface hydrophobicity of B. cereus vegetative cells from the late stationary phase was the highest followed by those from the stationary phase and the log phase cultures. While the vegetative cells prepared from stationary phase and log phase cultures, respectively, had the highest and the lowest surface charges. Adhesion of B. cereus vegetative cells to stainless steel was positively correlated with the cell surface hydrophobicity (R = 0.979). Surface hydrophobicity and surface positive charge noted on the spores harvested from diluted tryptic soy agar (DTSA) and Mn2+-tryptone glucose extract agar were higher than those harvested from the sucrose or lactose-added DTSA. A wide variation in the surface charge values was noted on the surface of various spores prepared from cultures grown on the four different media tested, while their ability to adhere to stainless steel chips in phosphate buffered saline (PBS) showed no significant difference (p > 0.05). Similarly, the number of spores or vegetative cells adhering to stainless steel suspended in PBS, milk or diluted milk (1000 x) did not differ significantly (p > 0.05).