Polyesters Based on Linoleic Acid for Biolubricant Basestocks: Low-Temperature,Tribological and Rheological Properties

Presently, plant oils which contain high percentage of linoleic acid 1 are perceived to be a viable alternative to mineral oil for biolubricant applications due to their biodegradability and technical properties. In order to get biodegradable lubricant, triester derivatives compounds (1–5) were synthesized and characterized. The processes involved were monoepoxidation of linoleic acid 2, oxirane ring opening 3, esterification 4 and acylation 5. The structures of the products were confirmed by FTIR, ¹H and ¹³C-NMR and LC-MS. The results that showed lowest temperature properties were obtained for triester 5, with a pour point value (PP) of -73°C, highest onset temperature (260°C) and lowest volatility at 0.30%. Viscosity index (VI) increased for the ester’s synthetic compounds (2, 3, 4, 5), while the PP decreased. This behavior is the result of the increase of the chain length of the branching agents. Triester based linoleic acid has improved properties such as low-temperature and tribological properties. These results will make it feasible for plant oil to be used for biolubricants, fuels in chain saws, transmission oil and brake fluid.     

The influence of structural components of alkyl esters on their anaerobic biodegradation in marine sediment

Ester-based organic compounds are one type of synthetic base fluid added to drilling mud used during off-shore oil-drilling operations in the Gulf of Mexico. Concern over the environmental impact of synthetic base fluid (SBF) contaminated rock cuttings discharged into the Gulf of Mexico has prompted the promulgation of EPA regulations requiring that all SBF be tested for biodegradability in marine sediment prior to their use in the Gulf. In order to allow the design or selection of suitably biodegradable esters, the anaerobic biodegradability of a variety of ester compounds was tested using a marine sediment inoculum to reveal the effect of: (a) increasing the chain length of the acid moiety, (b) increasing the chain length of the alcohol moiety; (c) alternating the relative size of the alcohol and acid moieties, (d) branching in the alcohol moiety, and (e) the presence of an unsaturated bond in the acidic moiety. The chemical structure of esters was found to affect the completeness and rate of anaerobic biodegradation, and would affect their ability to be certified for use as an SBF in the Gulf of Mexico. Recommendations for ester usage include using esters that have a total carbon number of between 12 and 18 and avoiding the use of branched alcohols (or acids by inference). The presence of an unsaturated bond in the acid (or alcohol by inference) increased biodegradability of the ester.     

Viscosity properties of mineral paraffinic base oils as a key factor in their primary biodegradability

The primary biodegradability of two types of paraffinic base oils (solvent and catalytically dewaxed oils) and their blends was evaluated using the CEC L-33-A-93 test. The biodegradability values varied between 10% and 75%. Base oil mixtures displayed varying contents in aromatic and polar compounds and a wide range of kinematic viscosity (KV) values, from roughly 10 to 600 cSt (at 40°C), while their viscosity indices were almost constant (90-100). The biodegradability of oils was closely related to their content in polycyclic aromatic hydrocarbons and was also decreasing with kinematic viscosity. For the two types of base oils, a linear relationship could be set between the biodegradation percentages and the logarithms of KV values. These results show that, beside overall chemical features such as the contents in aromatic compounds, KV may be a prominent parameter for assessing the primary biodegradability of mineral base oils.     

Effect of pretreatment of rubber material on its biodegradability by various rubber degrading bacteria

The effect of pretreatment of several cis-1,4-polyisoprene containing rubbers on their biodegradability was examined. Tests were carried out with six recently isolated and characterized rubber degrading bacteria belonging to the genera Gordonia (strains Kb2, Kd2 and VH2), Mycobacterium, Micromonospora and Pseudomonas. All strains were able to use natural rubber (NR) as well as NR latex gloves as sole carbon source. Extraction of NR latex gloves by organic solvents resulted in an enhancement of growth for three of the selected strains. On the other hand, growth of Gordonia sp. (strain Kb2 and Kd2), Mycobacterium fortuitum NF4 and Micromonospora aurantiaca W2b on synthetic cis-1,4-polyisoprene did only occur after removal of the antioxidants, that are usually added during manufacture to prevent aging of the materials. Detailed degradation studies performed with Gordonia sp. Kb2 revealed an enhanced mineralization of pretreated NR latex gloves and mineralization of purified natural rubber (NR), indicating the actual mineralization of cis-1,4-polyisoprene rubber constituent even after removal of non-rubber constituent that may act as co-metabolic substrate and support microbial growth. Further analysis by scanning electron microscopy (SEM) clearly demonstrated the enhanced colonization efficiency of these bacteria towards pretreated NR latex gloves. Colonization was additionally visualized by staining of overgrown NR latex gloves with Schiff's reagent, and the purple color produced in the area of degradation was an evidence for the accumulation of aldehydes containing oligomers. Further enhancement of latex gloves degradation could be achieved after successive replacement of mineral salts medium during cultivation. Thereby, a rapid disintegration of untreated NR latex gloves material was accomplished by Gordonia sp. strain VH2.     

Total Degradation of EDTA by Mixed Cultures and a Bacterial Isolate

A bacterial mixed culture, which was obtained from sewage by a special enrichment procedure, utilized EDTA as the sole source of carbon and nitrogen for growth. High concentrations of mineral salts, particularly CaCl₂, or the use of a mineral base without nitrogen protected the cells from inactivation after transfer into fresh medium containing 200-mg/liter (0.67 mM) EDTA. The chemical speciation did not influence the biodegradability of EDTA. However, when resting cells of the mixed culture were incubated with EDTA in the presence of an equivalent molar amount of FeCl₃, the reaction came to a halt before the complete consumption of the substrate. A gram-negative isolate from the mixed population, BNC1, also metabolized EDTA in monoculture. Growth of the pure culture was promoted by biotin or folic acid but was always accompanied by the accumulation of unidentified metabolites and was slow (μ_max, 0.024 h^-1) compared with that of the original community (μ_max, 0.036 h^-1).     

Bacterial degradation of hydrocarbons as evidenced by respirometric analysis

The microbial biodegradability of mineral oil and other hydrocarbons, namely hexane, decane and tetradecane was determined using the Warburg constant volume respirometer. Results of oxygen uptake indicated that hexane and tetradecane were more degradable than mineral oil and decane. Rhodococcus erythropolis and Erwinia cancerogena showed the highest (0.866) and lowest (0.115) oxygen quotient (Qo2) values, respectively, when exposed to mineral oil. Staphylococcus warneri and Enterobacter cloacae showed the highest (2.895) and (2.816) Qo2 values, respectively, when exposed to hexane; whereas E. cloacae and E. cancerogena showed the lowest Qo2 values (1.289 and 1.824), respectively. Both R. erythropolis and E. cloacae had the highest Qo2 values (2.859 and 2.289), respectively, when exposed to tetradecane. More oxygen was consumed by R. erythropolis than the other bacterial cultures when exposed to all hydrocarbons. In contrast, less oxygen was taken by E. cancerogena than the other bacterial cultures when exposed to all hydrocarbons, except for hexane.     

Feasibility of anaerobic co-digestion as a treatment option of meat industry wastes

The anaerobic biodegradability of meat industry wastes was investigated in mesophilic batch reactors and combined with a mathematical model for describing their biodegradable fractions. The characteristics and methane yield achieved when digesting waste sludge, suggested the use of this as co-substrate for enhancing the biodegradability of the other wastes. The co-digestion experiments showed that it would be feasible to co-digest cow manure or ruminal waste with waste sludge, but biodegradability of pig/cow slurries was not improved, being strongly influenced by the ammonium concentration of co-digestion mixture. By applying the mathematical model, it was observed that when increasing the amount of waste sludge in the co-digestion mixtures, the amount of inert and slowly biodegradable fractions decreased leading to an increase in readily biodegradable fractions, volatile solid removal efficiencies and methane yields. These results suggest that using readily biodegradable wastes as co-substrate, the anaerobic biodegradability of complex organic wastes can be improved.     

Characterization of cellulose acetate-reinforced aliphatic-aromatic copolyester composites

The biodegradability, morphology, mechanical, and thermal properties of composite materials composed of maleic anhydride-grafted poly(butylene adipate-co-terephthalate) (PBAT) and cellulose acetate (CA) were evaluated. Composites containing maleic anhydride-grafted PBAT (PBAT-g-MA/CA) exhibited noticeably superior mechanical properties due to greater compatibility between the two components. The dispersion of CA in the PBAT-g-MA matrix was highly homogeneous as a result of ester formation, and the consequent creation of branched and cross-linked macromolecules between the anhydride carboxyl groups of PBAT-g-MA and hydroxyl groups in CA. Each composite was buried in soil and monitored to assess biodegradability. Both the PBAT and the PBAT-g-MA/CA composite films were eventually completely degraded, and severe disruption of film structure was observed after 60-100 days of incubation. Although the degree of weight loss after burial indicated that both materials were biodegradable, even with high levels of CA, the higher water resistance of PBAT-g-MA/CA films indicated that they were more biodegradable than those made of PBAT.     

Effects of Multivitamin/Mineral Supplementation on Trace Element Levels in Serum and Follicular Fluid of Women Undergoing in Vitro Fertilization (IVF)

We investigated effects of multivitamin/mineral supplementation on element levels in serum and follicular fluid of women undergoing IVF. We used three groups in this study. The first group was used as an age-matched and nonpregnant control (n = 13). Group 2 (n = 30) constituted the IVF group and women in the third group who were undergoing IVF also received a multivitamin/mineral tablet daily for 45 days. Follicular fluid and serum selenium and zinc levels and follicular fluid copper levels were lower in IVF patients than in controls although follicular fluid aluminum and iron levels were higher in IVF patients than in controls. However, follicular fluid and serum aluminum, copper, zinc and selenium levels, and serum magnesium levels were higher in the multivitamin/mineral group than in the IVF group although follicular fluid iron levels were lower in the multivitamin/mineral group than in the IVF group. In conclusion, we observed that copper, zinc, and selenium in serum and follicular fluid decreased in women undergoing IVF. Multivitamin/mineral supplementation in serum and follicular fluid of women undergoing IVF normalized the trace element levels.     

Effects of thermo-chemical pre-treatment on anaerobic biodegradability and hydrolysis of lignocellulosic biomass

The effects of different thermo-chemical pre-treatment methods were determined on the biodegradability and hydrolysis rate of lignocellulosic biomass. Three plant species, hay, straw and bracken were thermo-chemically pre-treated with calcium hydroxide, ammonium carbonate and maleic acid. After pre-treatment, the plant material was anaerobically digested in batch bottles under mesophilic conditions for 40 days. From the pre-treatment and subsequent anaerobic digestion experiments, it was concluded that when the lignin content of the plant material is high, thermo-chemical pre-treatments have a positive effect on the biodegradability of the substrate. Calcium hydroxide pre-treatment improves the biodegradability of lignocellulosic biomass, especially for high lignin content substrates, like bracken. Maleic acid generates the highest percentage of dissolved COD during pre-treatment. Ammonium pre-treatment only showed a clear effect on biodegradability for straw.     

Measuring the influence of environmental conditions on dissolved organic matter biodegradability and optical properties: a combined field and laboratory study

Fluorescence spectroscopy is a common tool to assess optical dissolved organic matter (DOM) and a number of characteristics, including DOM biodegradability, have been inferred from these analyses. However, recent findings on soil and DOM dynamics emphasize the importance of ecosystem-scale factors, such as physical separation of substrate from soil microbial communities and soil physiochemical cycles driving DOM stability. We apply this principle to soil derived DOM and hypothesize that optical properties can only supply information on biodegradability when evaluated in the larger ecosystem because substrate composition and the activity/abundance of the microbial community ultimately drive DOM degradation. To evaluate biodegradability in this context, we assessed aqueous soil extracts for water extractable organic carbon (WEOC) content, biodegradability, microbial biomass and DOM characteristics using fluorescence spectroscopy across a range of environmental conditions (covariant with season and land use) in northern Vermont, USA. Our results indicate that changes in environmental conditions affect composition, quantity, and biodegradability of DOM. WEOC concentrations were highest in the fall and lowest in the summer, while no significant differences were found between land covers; however, DOM biodegradability was significantly higher in the agricultural site across seasons. Despite a shift in utilized substrate from less aromatic DOM in summer to more aromatic DOM in winter, biodegradability was similar for all seasons. The only exception was cold temperature incubations where microbial activity was depressed, and processing was slowed. These results provide examples on how fluorescence based metrics can be combined with context relevant environmental parameters to evaluate bioavailability in the context of the larger ecosystem.

     

On the release of fluoride from biofilm reservoirs during a cariogenic challenge: an in situ study

Abstract

Biofilm fluoride reservoirs may be a source of fluoride to the fluid phase during a sugar challenge reducing tooth mineral loss. However, the evidence for that is conflicting and has not been studied in biofilms containing different fluoride levels. In order to test fluoride release from biofilms with distinct fluoride concentrations, biofilms were grown in situ exposed to a combination of placebo, calcium and fluoride rinses forming biofilms with no (fluoride-free rinses), low (fluoride-only rinses) or high (calcium followed by fluoride rinses) fluoride concentrations, and collected before and 5?min after a sucrose challenge. Rinsing with fluoride increased fluoride concentration in the biofilm (p?<?0.05), mainly when a calcium pre-rinse was used before the fluoride (p?<?0.05). However, after a sugar challenge, no significant increase in the biofilm fluid fluoride concentration was observed, even in the fluoride-rich biofilms (p?>?0.05). Fluoride-rich biofilms do not release fluoride to the fluid phase during a sugar challenge.     

Optimisation of in vitro culture conditions in B6CBF1 mouse embryos

This study was undertaken to investigate the effects of three media, volume and type of oil and frequency of observation on the in vitro development of mouse zygotes. B6CBF1 female mice (4 to 6 wk old) were superovulated using PMSG/hCG and mated with a proven fertile male of the same strain. Putative zygotes with polar bodies were collected from the oviducts of mated mice, 25-28 h after hCG injection, and were cultured in vitro. Embryo development was evaluated at either 96 h and 120 h or every 24 h for 120 h. The results obtained showed that the CZB medium was better than the KSOM and HCO3HTF media, and the use of 1 mL of paraffin oil was better than the use of 0.5 mL of paraffin oil. The effect of paraffin oil and mineral oil on embryo development was examined and the results indicated that the use of paraffin oil was better than the use of mineral oil. Repeated observations did not influence the proportion of embryos developing to blastocysts.     

Mineral distribution in rat skeletons after exposure to a microgravity model

Exposure to space flight models induces changes in the distribution of bone mineral in the human skeleton that has the features of a gravitational gradient. Regional bone mineral measurements with dual energy x-ray absorptiometry (DEXA) in male adults exposed to head-down tilt bed rest for 30 days show non-significant decrements in the pelvis and legs with 10% increases in the head region. Horizontal bed rest for 17 weeks reveals losses of bone mineral ranging from 2.2 to 10.4% from the lumbar spine to the calcaneus and an increase of 3.4% in the skull. Investigation of this phenomena would be most definitively carried out in an animal model. One candidate is the flight simulation model in the rat which removes body weight from the hind limbs and induces a cephalad fluid shift by suspending the animal by the tail. Weanling rats exposed to this model showed bone mineral to be lower in the hind limbs and higher in the skull after 3 weeks. These findings are similar in older 200 g animals after 2 weeks tail suspension. The purpose of this study was to determine the effect of age on the distribution of skeletal mineral in this model.     

Reinforcing mechanisms of starch nanocrystals in a nonvulcanized natural rubber matrix

A phenomenological modeling approach was developed to try to understand the reinforcing mechanism of starch nanocrystals in a nonvulcanized natural rubber matrix. Natural rubber was not cross-linked to maintain the biodegradability of the biosourced materials. Nonlinear dynamic mechanical experiments highlighted the significant reinforcing effect of starch nanocrystals and the presence of the Mullins and Payne effects. Two models were used to predict the Payne effect considering that either filler-filler (Kraus model) or matrix-filler (Maier and Go?ritz model) interactions are preponderant. The use of the Maier and Goritz model demonstrated that phenomena of adsorption and desorption of NR chains on the filler surface governed nonlinear viscoelastic properties, even if the formation of a percolating network for filler contents >6.7 vol % was evidenced by the Kraus model.     

生菜矿质养分特性的品种差异比较研究

为了探明生菜不同品种类型之间的矿质养分特性差异,本实验采用深水栽培方式,比较研究了玻璃生菜、油麦菜和意大利生菜3个品种在不同生长时期地上部Fe、Zn、Ca含量的差异,以及根际缺氧处理对3个品种地上部Fe、Zn、Ca含量的影响.结果表明,随着植株的生长,3个品种地上部的Fe、Zn、Ca含量均呈上升趋势,到出苗后50 d达到最高水平,随后稍有下降.3个品种地上部3种矿质养分含量由高到低的顺序依次是：意大利生菜、玻璃生莱、油麦菜.但3个品种地上部的生长速率的大小顺序却相反.根际缺氧处理（以正常通气栽培植株作对照）均使3个品种地上部的Fe、Zn、Ca含量下降,其中意大利生菜所受的影响最大,其地上部的Fe、Zn、Ca含量分别比对照降低18.04%、12.70%、17.56%;油麦菜的影响最小,其地上部Fe、Zn、Ca含量的降低率不及意大利生菜的一半;玻璃生菜地上部Fe、Ca含量受影响比较大,分别比对照降低10.54%和14.79%,但Zn含量的影响比较小.     

Degradation of Microbicides under Different Environmental Conditions

To determine the biodegradability of some widely used microbicides, these products were dissolved in a mineral solution and synthetic sewage and their breakdown was followed under aerobic and anaerobic conditions. The results indicated that most biocides will not raise pollution problems provided they are discharged into domestic sewage and subsequently treated by aerobic water purification systems. However, all but a few of the biocides tested failed to be degraded in tests simulating conditions prevailing in oligotrophic aquatic systems or in anaerobic ecosystems.     

Ultrastructure of Cryptococcus neoformans in the cerebrospinal fluid of a patient with cryptococcal meningitis

The ultrastructure of Cryptococcus neoformans in the cerebrospinal fluid, which was obtained from a patient suffering from systemic lupus erythematosus and cryptococcal meningitis, before treatment and on the 10th and 20th day after the start of treatment was studied. Numerous cryptococci were detected in the cerebrospinal fluid before treatment. However, in most of them their biological activity was low and their organelles were not clear. A few yeasts preserved well their organelles. Such cells showed a tendency to develop vesicular membrane structures (lomasomes) touching the internal part of the cell wall. In the cerebrospinal fluid on the 20th day all of the yeasts were dead, even though numerous yeasts were observed by an India-ink method. At this time no colonies were recovered from the fluid.     

Synthesis and characterization of sugar-bearing chitosan derivatives: aqueous solubility and biodegradability

The extended use of chitosan in biomedical fields has been limited by its insoluble nature in a biological solution. To endow the water solubility in a broad range of pH, chitosan derivatives were prepared by the covalent attachment of a hydrophilic sugar moiety, gluconic acid, through the formation of an amide bond. These sugar-bearing chitosans (SBCs) were further modified by the N-acetylation in an alcoholic aqueous solution. Thereafter, the effect of the gluconyl group and the degree of N-acetylation (DA) on the water solubility at different pHs and on the biodegradability of chitosan were investigated. The SBCs showed the water solubility in a broader range of pH than chitosan, whereas they were still insoluble at neutral and alkali pH. The N-acetylation of SBCs significantly affected the water solubility, for example, the SBCs with the DA, ranging from 29% to 63%, were soluble in the whole range of pH. This might result from the improved hydrophilicity by the gluconyl group, accompanied by the role of the N-acetyl group that disturbed the hydrogen bonding between amino groups of chitosan. From the biodegradation tests, determined by the decrease in the viscosity of a polymer solution exposed to lysozyme, it was evident that the gluconyl group attached to chitosan improved the biodegradability. Thus, it was possible to control the biodegradability of chitosan by adjusting the amounts of gluconyl and N-acetyl groups in the chitosan backbone. The N-acetylated SBCs, soluble in the broad range of pH, might be useful for various biomedical applications.     

Promotion and nucleation of carbonate precipitation during microbial iron reduction

Iron‐bearing early diagenetic carbonate cements are common in sedimentary rocks, where they are thought to be associated with microbial iron reduction. However, little is yet known about how local environments around actively iron‐reducing cells affect carbonate mineral precipitation rates and compositions. Precipitation experiments with the iron‐reducing bacterium Shewanella oneidensis MR‐1 were conducted to examine the potential role of cells in promoting precipitation and to explore the possible range of precipitate compositions generated in varying fluid compositions. Actively iron‐reducing cells induced increased carbonate mineral saturation and nucleated precipitation on their poles. However, precipitation only occurred when calcium was present in solution, suggesting that cell surfaces lowered local ferrous iron concentrations by adsorption or intracellular iron oxide precipitation even as they locally raised pH. Resultant precipitates were a range of thermodynamically unstable calcium‐rich siderites that would likely act as precursors to siderite, calcite, or even dolomite in nature. By modifying local pH, providing nucleation sites, and altering metal ion concentrations around cell surfaces, iron‐reducing micro‐organisms could produce a wide range of carbonate cements in natural sediments.