Heavy metals (mercury, arsenic, cadmium, plumbum) in selected marine fish and shellfish along the Straits of Malacca

Level of heavy metals in marine ecosystem has been intensively studied during recent years as these hazardous substances could be accumulated in the biota. Generally, the presence of contaminants in fish is a result of human activities such as industrial and agricultural wastes. In this study, the marine fish and shellfish from the Straits of Malacca were analyzed using Inductively Coupled Plasma Optical Emission Spectrophotometer (ICP-OES) and Flow Injection Mercury System (FIMS) for Cd, As and Pb and Hg, respectively. The Straits of Malacca is one of the busiest shipping routes in the world that make the level of heavy metals potentially high besides the various industrial activities along the west region of Peninsular Malaysia. The range of heavy metals in samples were 1.0-3-6.5-3 μg/ g wet sample for Hg, 0.5-2-47-2 μg/ g wet sample for Cd, 0.01-0.39 μg/ g wet sample for Pb and 0.14-6.57 μg/ g wet sample for As. Most part of the values was below the permitted limit set by FAO/WHO 2004 as well as Food Act 1983 and Food Regulations 1985. Therefore it can be generalized that fish and shellfish from the Straits of Malacca are safe to consume in terms of these heavy metals concentration and do not constitute a risk for human health

Biological Remediation of Cyanide: a Review

Cyanide and its complexes are produced by industries all over the world as waste or effluents. Biodegradation is considered to be the cheapest and the most effective method to get rid of cyanide in the environment. Several studies on different types of microorganisms that can degrade cyanide in the environment have been carried out. Hydrolytic, oxidative, reductive, and substitutive/transfer reactions are some of the common pathways used by microorganisms in cyanide degradation. Biodegradation of cyanide can occur aerobically or an-aerobically depending on the environmental conditions. Immobilised enzymes or microorganisms prove to be very effective method of degradation. Microorganisms such as Klebsiella oxytoca, Corynebacterium nitrophilous, Brevibacterium nitrophilous, Bacillus spp., Pseudomonas spp. and Rhodococcus UKMP-5M have been reported to be very effective in biodegradation of cyanide

Isolation and characterization of an SDS-degrading Klebsiella oxytoca.

Sodium dodecyl sulfate (SDS) is one of the main components in the detergent and cosmetic industries. Its bioremediation by suitable microorganism has begun to receive greater attention as the amount of SDS usage increases to a point where treatment plants would not be able to cope with the increasing amount of SDS in wastewater. The purpose of this work was to isolate local SDS-degrading bacteria. Screening was carried out by the conventional enrichment-culture technique. Six SDS-degrading bacteria were isolated. Of these isolates, isolate S14 showed the highest degradation of SDS with 90% degradation after three days of incubation. Isolate S14 was tentatively identified as Klebsiella oxytoca strain DRY14 based on carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. SDS degradation by the bacterium was optimum at 37 degrees 0. Ammonium sulphate; at 2.0 g l(-1), was found to be the best nitrogen source for the growth of strain DRY14. Maximum growth on SDS was observed at pH 7.25. The strain exhibited optimum growth at SDS concentration of 2.0 g l(-1) and was completely inhibited at 10 g l(-1) SDS. At the tolerable initial concentration of 2.0 g l(-1), almost 80% of 2.0 g l(-1) SDS was degraded after 4 days of incubation concomitant with increase in cellular growth. The K(m(app) and V(max(app)) values calculated for the alkylsulfatase from this bacterium were 0.1 mM SDS and 1.07 micromol min(-1) mg(-1) protein, respectively

Assay for heavy metals using an inhibitive assay based on the acetylcholinesterase from Pangasius hypophthalmus (Sauvage, 1878)

Acetylcholinesterase (AChE) is generally used as an inhibitive assay for insecticides. A lesser-known property of AChE is its inhibition by heavy metals. In this work, we evaluate an AChE from silver catfish brain (Pangasius sp.), wasted from aquaculture industry, as an inhibitive assay for heavy metals. We discovered that the AChE was completely inhibited by Cr6+, Ag2+, Cd2+, Hg2+, Cu2+, Zn2+ and Pb2+ during an initial screening. When testing at various concentrations, the above heavy metals exhibited exponential decay type inhibition curves. The calculated IC50 for Hg2+, Cu2+, Ag2+, Cr6+, Cd2+, Pb2+, and Zn2+ were 0.071, 0.088, 0.088, 0.87, 0.913, 1.1, and 1.572 mg/L, respectively. The Limit of Detection (LOD) and Limit of Quantification (LOQ) values of the heavy metals are within the range of the Maximum Permissibility Limit (MPL) allowed by the Malaysian Department of Environment (DOE) for Class-III rivers. The IC50 values for these heavy metals are comparable, and some are lower than those of the currently known assays, such as immobilised urease, Daphnia magna, MicrotoxTM, rainbow trout, papain and bromelain assays. Field trial works on an industrial drainage site had shown that the developed assay is applicable in detecting heavy metals in the water. The assay can be carried out in less than 30 min under ambient temperature

Characterization of a sodium dodecyl sulphate-degrading Pseudomonas sp. strain DRY15 from Antarctic soil

A bacterium capable of biodegrading surfactant sodium dodecyl sulphate (SDS) was isolated from Antarctic soil. The isolate was tentatively identified as Pseudomonas sp. strain DRY15 based on carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. Growth characteristic studies showed that the bacterium grew optimally at 10 degrees C, 7.25 pH, 1 g l(-1) SDS as a sole carbon source and 2 g l(-1) ammonium sulphate as nitrogen source. Growth was completely inhibited at 5 g l(-1) SDS. At a tolerable initial concentration of 2 g l(-1), approximately 90% of SDS was degraded after an incubation period of eight days. The best growth kinetic model to fit experimental data was the Haldane model of substrate inhibition with a correlation coefficient value of 0.97. The maximum growth rate was 0.372 hr(-1) while the saturation constant or half velocity constant (Ks) and inhibition constant (Ki), were 0.094% and 11.212 % SDS, respectively. Other detergent tested as carbon sources at 1 g l(-1) was Tergitol NP9, Tergitol 15S9, Witconol 2301 (methyl oleate), sodium dodecylbenzene sulfonate (SDBS), benzethonium chloride, and benzalkonium chloride showed Tergitol NP9, Tergitol 15S9, Witconol 2301 and the anionic SDBS supported growth with the highest growth exhibited by SDBS

Assay for heavy metals using an inhibitive assay based on the acetylcholinesterase from Pangasius hypophthalmus (Sauvage, 1878)

Acetylcholinesterase (AChE) is generally used as an inhibitive assay for insecticides. A lesser-known property of AChE is its inhibition by heavy metals. In this work, we evaluate an AChE from silver catfish brain (Pangasius sp.), wasted from aquaculture industry, as an inhibitive assay for heavy metals. We discovered that the AChE was completely inhibited by Cr6+, Ag 2+, Cd2+, Hg2+, Cu2+, Zn 2+ and Pb2+ during an initial screening. When testing at various concentrations, the above heavy metals exhibited exponential decay type inhibition curves. The calculated IC50 for Hg2+, Cu 2+, Ag , Cr6+, Cd2+, Pb2+, and Zn2+were 0.071, 0.088, 0.088, 0.87, 0.913, 1.1, and 1.572 mg/L, respectively. The Limit of Detection LOD and Limit of Quantification LOQ values of the heavy metals are within the range of the Maximum Permissibility Limit MPL allowed by the Malaysian Department of Environment DOE for Class-Ill rivers. The IC50 values for these heavy metals are comparable, and some are lower than those of the currently known assays, such as immobilised urease, Daphnia magna, Microtox™, rainbow trout, papain and bromelain assays. Field trial works on an industrial drainage site had shown that the developed assay is applicable in detecting heavy metals in the water. The assay can be carried out in less than 30 min under ambient temperature

Physical Performance and Cross Layer Design for Wireless Mesh Networks

Wireless mesh networks (WMNs) are an alternative technology for last-mile broadband Internet access that can support broadband services. However, for a WMN to be all it can be, considerable research efforts are still needed. In WMNs, the Orthogonal Frequency Division Multiplexing (OFDM) system is chose to provide the better performance at the physical layer design. OFDM is very tolerant to ISI and it's spectrally efficient. OFDM also very susceptible to phase and frequency offsets. This paper presents the physical layer design of an OFDM system for wireless mesh networkin

Studies on seed germination and growth in weed species of rice field under salinity stress.

An investigation was made to see the salt tolerance of 10 weed species of rice. Properly dried and treated seeds of weed species were placed on 9 cm diameter petridishes lined with Whatman No. 1 filter paper under 6 salinity regimes, viz. 0 (control), 4, 8, 16, 24 and 32 dS m-1. The petri dishes were then kept in germinator at 25±1.0oC and 12 hr light. The number of germinated seeds were recorded daily. The final germination percentage, germination index (GI), seedling vigour index, mean germination time and time for 50% germination were estimated. Root and shoot lengths of the weed seedlings were measured at 20 days after salt application and relative growth values were calculated. Results revealed that salinity decreased final germination percentage, seed of germination as measured by GI, and shoot and root length in all the species. Germination of most of the weed seeds was completely arrested (0) at 32 dS m-1 salinity except in E. colona (12%) and C. iria (13.9%). The species C. iria, E. colona, J. linifolia and E. crusgalli showed better germination (above 30%) upto 24 dS m-1 salinity level and were regarded as salt-tolerant weed species. J. linifolia, F. miliacea, L. chinensis and O. sativa L. (weedy rice) were graded as moderately tolerant and S. zeylanica, S. grosus and C. difformis were regarded as least tolerant weed species

Characterization of Injection Molded 17-4PH Stainless Steel Prepared with Waste Rubber Binder

This study is to investigate the sintering characteristics and to establish the best heating rate and soaking time used for sintering process, by determining the physical, mechanical, and microstructural properties of the injection molded 17-4PH stainless steel using waste rubber as a new developed binder system. By using the feedstock which having 65 vol.% of metal powder, the molding are injected into the tensile test bar and immediately processed with two stage debinding process that involves of solvent extraction and thermal pyrolisis to remove the binder. The specimens were sintered at 1360°C under vacuum atmosphere and tested for a critical property analysis of tensile test. Later, the observation on tensile testedspecimens fracture surface are done to understand the fracture behavior,distribution of grain and porosity and the significant correlation of fracture morphology to the mechanical properties. From this study, it is found that the combination of 50C/min heating rate and 60 minutes of soaking period resulted in higher density value, higher tensile strength, less porosity and homogenous grains distribution of the sintered specimens