The effectiveness of the e-money incentive mechanism in promoting separation of recyclables at source in Malaysia

Journal of Material Cycles and Waste Management - A new concept of a reward system by two e-money-incentive systems aimed at improving separation at source toward reducing residual waste generation...     

Impact of gamma irradiation on the transformation efficiency for extracellular plasmid DNA

Extracellular DNA is omnipresent in aquatic environments and is thought to be a genetic material for horizontal gene transformation between microorganisms. We studied the impact of gamma irradiation on the transformation efficiency (transformants number per ng of DNA per ml) of extracellular DNA. Plasmid pEGFP as a model extracellular DNA was irradiated by gamma rays. The transformation efficiency decreased with the increase in radiation dose. A total dose of 10Gy is normally not lethal for microorganisms but certainly affects the transformation efficiency of extracellular DNA. The decrease in the efficiency would be induced by strand breaks of extracellular DNA because the yield of both single-strand breaks (SSBs) and double-strand breaks (DSBs) increased with the increase in radiation dose. The relative transformation efficiency of SSBs and DSBs to that of covalently closed circles (CCCs) was 30.3% and 0.2%, respectively. This impact on natural transformation suggests an inability of microorganisms to acquire new characteristics which should be normally acquired.     

Effects of acute γ-irradiation on the aquatic microbial microcosm in comparison with chemicals

Effects of acute γ-irradiation were investigated in the aquatic microcosm consisting of green algae (Chlorella sp. and Scenedesmus sp.) and a blue–green alga (Tolypothrix sp.) as producers; an oligochaete (Aeolosoma hemprichi), rotifers (Lecane sp. and Philodina sp.) and a ciliate protozoan (Cyclidium glaucoma) as consumers; and more than four species of bacteria as decomposers. At 100 Gy, populations were not affected in any taxa. At 500–5000 Gy, one or three taxa died out and populations of two or three taxa decreased over time, while that of Tolypothrix sp. increased. This Tolypothrix sp. increase was likely an indirect effect due to interspecies interactions. The principal response curve analysis revealed that the main trend of the effects was a dose-dependent population decrease. For a better understanding of radiation risks in aquatic microbial communities, effect doses of γ-rays compared with copper, herbicides and detergents were evaluated using the radiochemoecological conceptual model and the effect index for microcosm.     

Isolation of a fungus from denitrifying activated sludge that degrades highly chlorinated dioxins

 This article reports the potential of denitrifying activated sludge to degrade highly chlorinated dioxins, especially from a (landfill) leacheate treatment plant in Japan, and the isolation from this denitrifying activated sludge of a microorganism able to degrade highly chlorinated dioxins. Using a 700-ml bioreactor, denitrifying activated sludge was cultivated under denitrifying conditions by adding 2.0 ng of a mixture of 4- to 8-chlorinated dioxins from fly ash. The dioxin contents of the sample, effluent, and medium before and after cultivation were measured by gas chromatography–mass spectrometry (GC–MS). After 7 days cultivation, about 90% of added dioxins were lost (average percentage of isomer depletion). A dioxin-degrading microorganism was isolated from the activated sludge. Lignin was added to the medium as a color indicator of aromatic compound degradation, and the lignin-decolorizing microorganisms in the denitrifying activated sludge were screened. Some strains were isolated, and one major isolated fungus, strain 622, decolorized lignin effectively. Strain 622 was identified as an Acremonium sp. from its morphological characteristics. It could decolorize lignin by 24% under paraffin-sealed anaerobic conditions. After the cultivation of strain 622 with a 2 ng/ml mixture of 4- to 8-chlorinated dioxins for 1 day, 82% (average for individual isomers) of the added 4- to 8-chlorinated dioxins had been degraded. Added octachlorodibenzo-p-dioxin (OCDD, 100 ng) was degraded under aerobic conditions after 8 h of incubation. During this process, heptachlorodibenzo-p-dioxin was produced and appeared to be a degradation product of OCDD. 1- or 2-hydroxydibenzo-p-dioxin from OCDD was also identified as the degradation product by GC–MS. These results indicated that OCDD was degraded to the nonchlorinated dibenzo-p-dioxins through dechlorination by Acremonium sp. strain 622. Received: October 12, 2001 / Accepted: March 11, 2002     

Recovery of gold by chicken egg shell membrane-conjugated chitosan beads

We have successfully prepared a bead-type adsorbent from two materials with different adsorption characteristics. Heavy metals were removed by greatly swollen egg shell membrane-conjugated chitosan beads. The egg shell membrane accumulated and removed precious metal ions from a dilute aqueous solution with a high affinity in a short contact time. Experiments suggested that chitosan beads could take up gold ions with great capacity and selectivity by conjugation with egg shell membrane. Under certain conditions, the selective removal of gold and copper in a mixture of gold and copper ions by egg shell membrane-conjugated chitosan beads was 100% and 2%, respectively. Egg shell membrane-conjugated chitosan beads can be seen as a promising material to recover gold in wastewater from various industries, such as electroplating.     

Histological study of the effects of starvation on reared and wild-caught larval stone flounder,Kareius bicoloratus

Starvation tolerance of laboratory-reared larval stone flounder, Kareius bicoloratus, was examined at different temperatures and salinities during the winters of 1984, 1985 and 1986. Starvation tolerance decreased with increased temperature and exhibited low values with high salinities. The highest starvation tolerance observed at low salinity was just before the metamorphosis stage. Starvation tolerance showed little change until larvae were 11 d. It increased with age thereafter. Epithelial cell heights of the digestive tract and cell diameters of pancreas and liver were measured histologically in reared stone flounder during growth and starvation. These values decreased markedly in the starved condition. Aldehyde fuchsin positive granules in the rectal epithelium also disappeared during the short starved period. The nutitrional condition of wild-caught stone flounder larvae, collected in January and February 1986 from the Matsukawa-ura inlet, Fukushima, Japan, was also examined. Eighty percent of larvae were estimated to be in fed condition just before sampling. The changes in cell heights of digestive organs agreed with this estimate. These histological methods seem to be useful in assessing the nutritional condition of marine fish larvae.