119 research outputs found
Production of Chitin and Chitosan from Shrimp Shell in Batch Culture of Lactobacillus plantarum
Lactobacillus plantarum, as a potential lactic acid and protease producer, was used for biological extraction of chitin from shrimp shell. L. plantarum was grown in a batch culture containing shrimp shell powder and date syrup, incubated at 30 °C. The produced
organic acids and proteases in L. plantarum culture were able to demineralize and deproteinize shrimp shell. Percentages of deproteinization and demineralization were 45 and 54, respectively. In post treatment of the sample, dilute acid and alkali, were implemented to produce the specific chitin. Chitin was converted to chitosan by N-deacetylation with NaOH solution. Percentage of deacetylation based on FTIR spectrum was 83 %
The Environmental Effect on Spawning Time, Length at Maturity and Fecundity of Kutum (R u t i l u s f r i s i i k u t u m , Kamensky, 1901) in Southern Part of Caspian Sea, Iran
Fish sampling were carried out using beach seines during the fishing season from early October 2006 to mid April 2007. The gonadosomatic indexes (GSI) in range and average for female and male were 0.03 to 40.28 (5.70 ± 6.48) and 0.13 to 16.71 (3.39 ± 2.33), respectively. The GSI indicated that the reproductions of R. f. kutum were occurred during March-April, with the highest average value of 6.52 for males and of 17.00 for females in April. Fifty percent of length maturity (Lm50%) at FL = 37.78 cm was recorded. The absolute fecundity ranged from 15,723 for a three-year old to 130,737 eggs for an eight-year old female, with a mean of 60435 ± 24889. The relationship between fecundity (F) and fork length (cm) was represented by the formula: Fec. = 6616FL+25916. The von Bertalanffy growth parameters was: Lâ=67.5cm, K=0.21 year-1, t0 =-0.10 for throw population of kutum. The maximum spawning migration into the rivers based on GSI occurred significantly in April but it may effects by environment of sea water layers. The results showed that the length at first maturity and fecundity of R. f. kutum is reduced in southern part of Caspian Sea
Rotating biological contactors : a review on main factors affecting performance
Rotating biological contactors (RBCs)
constitute a very unique and superior alternative
for biodegradable matter and nitrogen removal on
account of their feasibility, simplicity of design and
operation, short start-up, low land area requirement,
low energy consumption, low operating and maintenance
cost and treatment efficiency. The present
review of RBCs focus on parameters that affect
performance like rotational speed, organic and
hydraulic loading rates, retention time, biofilm support
media, staging, temperature, influent wastewater
characteristics, biofilm characteristics, dissolved oxygen
levels, effluent and solids recirculation, stepfeeding
and medium submergence. Some RBCs
scale-up and design considerations, operational problems
and comparison with other wastewater treatment
systems are also reported.Fundação para a CiĂȘncia e a Tecnologia (FCT
Proton Transfer, Hydrogen Bonding, and Disorder: Nitrogen Near-Edge X-ray Absorption Fine Structure and X-ray Photoelectron Spectroscopy of Bipyridine-Acid Salts and Co-crystals
The sensitivity of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to BrĂžnsted donation and the protonation state of nitrogen in the solid state is investigated through a series of multicomponent bipyridineâacid systems alongside X-ray photoelectron spectroscopy (XPS) data. A large shift to high energy occurs for the 1s â 1Ï* resonance in the nitrogen K-edge NEXAFS with proton transfer from the acid to the bipyridine base molecule and allows assignment as a salt (CâNH+), with the peak ratio providing the stoichiometry of the types of nitrogen species present. A corresponding binding energy shift for CâNH+ is observed in the nitrogen XPS, clearly identifying protonation and formation of a salt. The similar magnitude shifts observed with both techniques relative to the unprotonated nitrogen of co-crystals (CâN) suggest that the chemical state (initial-state) effects dominate. Results from both techniques reveal the sensitivity to identify proton transfer, hydrogen bond disorder, and even the potential to distinguish variations in hydrogen bond length to nitrogen
Systematic Review of Potential Health Risks Posed by Pharmaceutical, Occupational and Consumer Exposures to Metallic and Nanoscale Aluminum, Aluminum Oxides, Aluminum Hydroxide and Its Soluble Salts
Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007).
Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of âtotal Alâassumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold.
The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al+ 3 to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)+ 2 and Al(H2O)6 + 3] that after complexation with O2âąâ, generate Al superoxides [Al(O2âą)](H2O5)]+ 2. Semireduced AlO2âą radicals deplete mitochondrial Fe and promote generation of H2O2, O2 âą â and OHâą. Thus, it is the Al+ 3-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates.
Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer\u27s disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants.
The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances
Biodegradation of Phenanthrene by Mixed Culture Consortia in Batch Bioreactor using Central Composite Face-Entered Design
Biodegradation of Phenanthrene (PHE) was studied in aqueous culture to
demonstrate the potential of the mixed culture in degrading high
concentration of PHE. The experiments were conducted to monitor
biodegradation of Phenanthrene for duration of 6 days. Biodegradation
of PHE was successfully achieved in low and middle concentration by the
isolated mixed culture. A full factorial Central Composite Design of
experiments was used to construct response surfaces with the removal,
the extent of PHE degradation and the specific growth rate as
responses. The initial Phenanthrene concentration (X1) and the reaction
time (X2) were used as design factors. The result was shown that
experimental data fitted with the polynomial model. Analysis of
variance showed a high coefficient of determination value in the range
of 0.936â0.999. The maximum biodegradation of PHE in terms of the
removal of PHE (Y1) was found to be 0.100 mg/mg (degraded PHE/initial
PHE). The maximum extent of biodegradation relative to initial PHE
concentration and biomass (Y2) was 0.171 mg/mg/mg (degraded PHE/initial
PHE/biomass). This maximum biodegradation correspond to the factors
combination of middle level of PHE content (X1= 19.06 mg/L) and the
highest level of reaction time (X2 = 132.00 hours). The removal
efficiency of PHE biodegradation was achieved 100%. Polynomial model
was found useful to predict PHE degradation under the experimental
studied. It was observed that optimum biodegradation of PHE can be
successfully predicted by RSM
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