Isolation and characterization of marine-derived actinomycetes with cytotoxic activity from the Red Sea coast

Objective: To isolate and evaluate the cytotoxic activity of different actinomycetes species isolated from the Red Sea coast in Sharm el-Sheikh, Egypt.Methods: Forty actinomycetes strains were isolated from different sediments and seawater samples collected from the Red Sea coast in Egypt. Actinomycetes were recognized by morphological and microscopic examinations. Cell viability and cytotoxicity induced by the crude extracts on breast cancer cell lines MDA-MB-231 were assessed using methylene blue assay. The strains with promising cytotoxic activity were identified by sequencing and amplifying the 16 S r RNA genes. The antibacterial activities of the crude extracts were performed using Kirby–Bauer disc diffusion method.Results: The results indicated that five ethyl acetate extracts exhibited cytotoxicity towards breast cancer cell lines MDA-MB-231. The highest cytotoxic activity was found for the ethyl acetate extracts of EGY2 and EGY39. The isolate EGY3 was identified as a new Streptomyces species, while the actinomycete EGY22 was found to be a member of the genus Nocardiopsis sp. The crude extract of the isolate EGY8 showed slightly high antimicrobial activity against different test microorganisms.Conclusions: The results of the present study reveal that marine sediments of the Red Sea are a potent source of novel species of actinomycetes. The isolates may be useful in discovery of novel bioactive compounds and an important step in the development of microbial natural product research.

Immobilized silver nanoparticles on silica gel as an efficient catalyst in nitroarene reduction

Nanoparticles have properties that can be fine-tuned by their size as well as shape.Hence,there is significant current interest in preparing nano-materials of small size dispersity and to arrange them in close-packed aggregates.This letter describes a way of synthesising silver nanoparticles and their protection to aggregate by silica gel.The combination of catalytic quantities of immobilized silver nanoparticles with reductive ability of NaBH_4 efficiently reduces aromatic nitroarenes to the corresponding amines in aqueous medium.Noteworthy is that highly chemoselective reactions were achieved in the presence of other functional groups such as halogen and carboxylic acid groups.The silver particles immobilized on silica gel are stable in the presence of oxygen for several months.

Characters of the P_(CO)_2 and CO_2 Flux in the East China Sea in Autumn

P CO 2 of air and seawater samples from the East China Sea (ECS) were measured in situ in autumn, 1994. Ocean currents, terrestrial fluviation, biological activities, etc.,P CO 2 characters in air and seawater were investigated. CO 2 flux and its character in the East China Sea are discussed on the basis of theP CO 2 profiles of air and seawater. It was clear that the nearshore was the source of CO 2; and that the outer sea area was the sink of CO 2; and that the shelf area of the ECS is a net sink for atmospheric CO 2 in autumn.

Health Risk Assessment of Some Heavy Metals in Water and Sediment at Marsa-Matrouh, Mediterranean Sea, Egypt

In an attempt to evaluate the environmental quality of Marsa-Matrouh city which covered the most famous beaches in Egypt, an environmental risk assessment was performed, including a screening level ecological risk assessment. The aim of this work was to determine which metals could possibly pose toxic adverse ecological effects to marine organisms and to determine whether hot spots exist or not. To fulfill the goals of study, surfacial sediment and water samples were collected from ten different locations covering Marsa-Matrouh city during four seasons (2010-2011). The average concentrations of Cd, Cu, Fe, Ni, Pb and Zn were 2.381 ± 3.389, 9.307 ± 14.159, 68.969 ± 9.397, 2.642 ± 1.004, 16.712 ± 8.469, 31.168 ± 15.322 μg/l in water and 0.755 ± 0.240, 5.363 ± 1.581, 962.131 ± 975.084, 3.972 ± 2.180, 15.210 ± 4.434 and 24.608 ± 7.706 μg/g dry weight in sediment respectively. The concentrations of the investigated six metals in water were within the acceptable limits except for two stations (Cleopatra and El-Obayed) which exhibited higher values than the permissible level of Cd during autumn 2010. Metal pollution assessment for both water and sediment was studied. Heavy metal pollution index indicates that water is not critically polluted with respect to the investigated metals. For sediment samples, threshold effect concentrations (TEC HQ) were lower than 1 except for Cd which showed higher value than 1, indicating the possibility of occurrence of toxic adverse ecological effects to benthic organisms for Cd, while rare adverse ecological effects are expected to occur with respect to Cu, Ni, Pb and Zn.

Simultaneous Hydrogen Production with the Degradation of Naphthalene in Seawater Using Solar Light-Responsive Carbon-Modified (CM)-n-TiO₂Photocatalyst

The simultaneous photocatalytic production of hydrogen and degradation of naphthalene in seawater was successfully achieved using carbon modified titanium oxide (CM-n-TiO2) nanoparticles under natural sunlight illumination. Compared to unmodified titanium oxide (n-TiO2), CM-n-TiO2 nanoparticles exhibited significantly higher photocatalytic efficiency. It is considered that carbon modification is responsible for the significant enhancement in the observed photoactivity. The experimental results indicated that the simultaneous production of hydrogen and degradation of naphthalene was favorable at pH 8 and optimal catalyst dose of 1.0 g.L-1. The solar photocatalytic degradation of naphthalene in seawater using CM-n-TiO2 successfully fitted using Langmuir-Hinshelwood model, and can be described by pseudo-first order kinetic model.

Effective Photocatalytic Reduction of Cr(VI) by Carbon Modified (CM)-n-TiO2 Nanoparticles under Solar Irradiation

Photocatalytic reduction of toxic Cr(VI) was successfully achieved using carbon modified titanium oxide (CM-n-TiO2) nanoparticles under natural sunlight illumination. Modification of titanium oxide by carbon significantly enhanced the photocatalytic reduction of Cr(VI) under natural sunlight irradiation. The effects of various experimental parameters such as catalyst dose, initial concentration of Cr(VI), and solution pH on the reduction rate of Cr(VI) were investigated. The highest reduction rate of Cr(VI) was obtained at the optimal conditions of pH 5 and 2.0 g·L?1 of CM-n-TiO2. Interestingly, in the presence of phenol, as a sacrificial electron donor, the rate of Cr(VI) reduction was nearly 1.7 times higher than in its absence. The solar photoreduction of Cr(VI) in aqueous solution using CM-n-TiO2 obeyed a pseudo-first order kinetics according to the Langmuir-Hinshelwood model.