Violacein, violet pigment produced by Chromobacterium violaceum, has attracted much attention recently due to its pharmacological properties including antibacterial activity. The present study investigated possible antibacterial mode of action of violacein from C. violaceum UTM5 against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) strains. Violet fraction was obtained by cultivating C. violaceum UTM5 in liquid pineapple waste medium, extracted, and fractionated using ethyl acetate and vacuum liquid chromatography technique. Violacein was quantified as major compound in violet fraction using HPLC analysis. Violet fraction displayed bacteriostatic activity against S. aureus ATCC 29213 and methicillin-resistant S. aureus ATCC 43300 with minimum inhibitory concentration (MIC) of 3.9 μg/mL. Fluorescence dyes for membrane damage and scanning electron microscopic analysis confirmed the inhibitory effect by disruption on membrane integrity, morphological alternations, and rupture of the cell membranes of both strains. Transmission electron microscopic analysis showed membrane damage, mesosome formation, and leakage of intracellular constituents of both bacterial strains. Mode of action of violet fraction on the cell membrane integrity of both strains was shown by release of protein, K+, and extracellular adenosine 5'-triphosphate (ATP) with 110.5 μg/mL, 2.34 μg/mL, and 87.24 ng/μL, respectively, at 48 h of incubation. Violet fraction was toxic to human embryonic kidney (HEK293) and human fetal lung fibroblast (IMR90) cell lines with LC50 value of 0.998 ± 0.058 and 0.387 ± 0.002 μg/mL, respectively. Thus, violet fraction showed a strong antibacterial property by disrupting the membrane integrity of S. aureus and MRSA strains. This is the first report on the possible mode of antibacterial action of violet fraction from C. violaceum UTM5 on S. aureus and MRSA strains.
Recycled paper mill effluent (RPME) contains high levels of organic and solid compounds, causing operational problems for anaerobic biological treatment. In this study, a unique modified anaerobic inclining-baffled reactor (MAI-BR) has been developed to treat RPME at various initial chemical oxygen demand (COD) concentrations (1000-4000 mg/L) and hydraulic retention times (HRTs) (3 and 1 day). The COD removal efficiency was decreased from 96 to 83% when the organic loading rate (OLR) was increased from 0.33 to 4 g/L day. Throughout the study, a maximum methane yield of 0.25 L CH4/g COD was obtained, while the pH fluctuated in the range of 5.8 to 7.8. The reactor performance was influenced by the development and distribution of the microbial communities. Based on the next-generation sequencing (NGS) analysis, the microbial community represented a variety of bacterial phyla with significant homology to Euryarchaeota (43.06%), Planctomycetes (24.68%), Proteobacteria (21.58%), Acidobacteria (4.12%), Chloroflexi (3.14%), Firmicutes (1.12%), Bacteroidetes (1.02%), and others (1.28%). The NGS analysis showed that the microbial community was dominated by Methanosaeta concilii and Candidatus Kuenenia stuttgartiensis. This can be supported by the presence of filamentous and spherical microbes of different sizes. Additionally, methanogenic and anaerobic ammonium oxidation (ANAMMOX) microorganisms coexisted in all compartments, and these contributed to the overall degradation of substances in the RPME. Graphical abstract ᅟ.
The current study investigates the dynamic relationship between structural changes, real GDP per capita, energy consumption, trade openness, population density, and carbon dioxide (CO2) emissions within the EKC framework over a period 1971-2013. The study used the autoregressive distributed lagged (ARDL) approach to investigate the long-run relationship between the selected variables. The study also employed the dynamic ordinary least squared (DOLS) technique to obtain the robust long-run estimates. Moreover, the causal relationship between the variables is explored using the VECM Granger causality test. Empirical results reveal a negative relationship between structural change and CO2 emissions in the long run. The results indicate a positive relationship between energy consumption, trade openness, and CO2 emissions. The study applied the turning point formula of Itkonen (2012) rather than the conventional formula of the turning point. The empirical estimates of the study do not support the presence of the EKC relationship between income and CO2 emissions. The Granger causality test indicates the presence of long-run bidirectional causality between energy consumption, structural change, and CO2 emissions in the long run. Economic growth, openness to trade, and population density unidirectionally cause CO2 emissions. These results suggest that the government should focus more on information-based services rather than energy-intensive manufacturing activities. The feedback relationship between energy consumption and CO2 emissions suggests that there is an ominous need to refurbish the energy-related policy reforms to ensure the installations of some energy-efficient modern technologies.
The present study applied the use of sequential extraction technique and simple bioaccessibility extraction test to investigate the bioavailable fractions and the human bioaccessible concentration of metals collected from nine stations in surface sediment of the Bernam River. The concentrations of total and bioaccessible metals from different stations were in the range of 0.30-1.43 μg g(-1) and 0.04-0.14 μg g(-1) for total cadmium and bioaccessibility of cadmium, respectively, 6.20-288 μg kg(-1) and 2.06-8.53 μg kg(-1) for total mercury and bioaccessibility of mercury, respectively, and 9.2-106.59 μg g(-1) and 0.4-2.75 μg kg(-1) for total tin and bioaccessibility of tin, respectively. The chemical speciation of Cd in most sampling stations was in the order of oxidisable-organic > acid-reducible > residual > exchangeable, while the chemical speciation of Hg was in the order of exchangeable > residual > oxidisable-organic > acid-reducible and the chemical speciation of Hg was in the order of residual > oxidisable-organic > acid-reducible > exchangeable. The principal component analysis showed that the main factors influencing the bioaccessibility of mercury in surface sediments were the sediment total organic matter, cation exchange capacity, and easily, freely, or leachable and exchangeable fraction, and the factors influencing the bioaccessibility of tin were the total tin and cation exchange capacity, while the bioaccessibility of Cd in surface sediments was influenced by the only factor which is the easily, freely, or leachable and exchangeable fraction.
The present paper reports management of palm oil mill effluent (POME) mixed with palm-pressed fibre (PPF) POME-PPF mixture using eco-friendly, cost-effective vermicomposting technology. Vermicomposting of POME-PPF was performed to examine the optimal POME-PPF ratio with respect to the criteria of earthworm biomass and to evaluate the decomposition of carbon and nitrogen in different percentages of POME-PPF mixtures. Chemical parameters such as TOC, N, P and K contents were determined to achieve optimal decomposition of POME-PPF. On this basis, the obtained data of 50% POME-PPF mixture demonstrated more significant results throughout the experiment after addition of the earthworms. However, 60 and 70% mixtures found significant only in the last stages of the vermicomposting process. The decomposition rate in terms of -ln (CNt/CNo) showed that the 50% mixture has higher decomposition rate as compared to the 60 and 70% (k50% = 0.0498 day(-1)). The vermicomposting extracts (50, 60 and 70%) of POME-PPF mixtures were also tested to examine the growth of mung bean (Vigna radiata). It was found that among different extract dilutions, 50% POME-PPF vermicompost extract provided longer root and shoot length of mung bean. The present study concluded that the 50% mixture of POME-PPF could be chosen as the optimal mixture for vermicomposting in terms of both decomposition rate and fertilizer value of the final compost. Graphical abstract ᅟ.
This study investigated the effects and the possible mechanisms of intestinal content (IC) from laying hens on in vitro lead (Pb(2+)) biosorption of four probiotic bacterial strains (Bifidobacterium longum BB79, Lactobacillus paracasei Kgl6, Lactobacillus pentosus ITA23, and Lactobacillus acidipiscis ITA44). The total Pb(2+) removal capacity of the four probiotic strains, with and without capsule polysaccharides (CPSs), increased in the presence of IC compared to the control (without IC). SEM imaging revealed certain unidentified particles from the IC adhered on the surface of bacterial cells sorted out using flow cytometry. Follow-up experiment showed an overall trend of increase in the Pb(2+) removal capacity of the sorted bacteria, but statistically significant for L. pentosus ITA23 and B. longum BB79 after incubation with IC, particularly with the suspended solid portion of the IC. In addition, the Fourier transform infrared spectrophotometer data showed that functional groups such as C-H, O-H, C=O, and C-O-C which possibly associated with Pb(2+) binding were mainly presented in the suspended solid portion of IC. Putting the above together, we postulated that the enhanced Pb(2+) binding capacity the probiotic bacteria incubated in IC is due to the adherence of the yet to be identified particles which could much exist in suspended solid portion of IC containing negatively charged functional groups which bind with the positive Pb(2+) ions.
Palm oil mill wastes (palm kernel shell (PKS)) were used to prepare activated carbons, which were tested in the removal of colorants from water. The adsorbents were prepared by 1-h impregnation of PKS with ZnCl2 as the activating agent (PKS:ZnCl2 mass ratios of 1:1 and 2:1), followed by carbonization in autogenous atmosphere at 500 and 550 °C during 1 h. The characterization of the activated carbons included textural properties (porosity), surface chemistry (functional groups), and surface morphology. The dye removal performance of the different activated carbons was investigated by means of the uptake of methylene blue (MB) in solutions with various initial concentrations (25-400 mg/L of MB) at 30 °C, using a 0.05-g carbon/50-mL solution relationship. The sample prepared with 1:1 PKS:ZnCl2 and carbonized at 550 °C showed the highest MB adsorption capacity (maximum uptake at the equilibrium, q max = 225.3 mg MB / g adsorbent), resulting from its elevated specific surface area (BET, 1058 m2/g) and microporosity (micropore surface area, 721 m2/g). The kinetic experiments showed that removals over 90% of the equilibrium adsorptions were achieved after 4-h contact time in all the cases. The study showed that palm oil mill waste biomass could be used in the preparation of adsorbents efficient in the removal of colorants in wastewaters.
The study represents a comprehensive analysis of engine exhaust emission variation from a compression ignition (CI) diesel engine fueled with diesel-biodiesel blends. Biodiesel used in this investigation was produced through transesterification procedure from Moringa oleifera oil. A single cylinder, four-stroke, water-cooled, naturally aspirated diesel engine was used for this purpose. The pollutants from the exhaust of the engine that are monitored in this study are nitrogen oxide (NO), carbon monoxide (CO), hydrocarbon (HC), and smoke opacity. Engine combustion and performance parameters are also measured together with exhaust emission data. Some researchers have reported that the reason for higher NO emission of biodiesel is higher prompt NO formation. The use of antioxidant-treated biodiesel in a diesel engine is a promising approach because antioxidants reduce the formation of free radicals, which are responsible for the formation of prompt NO during combustion. Two different antioxidant additives namely 2,6-di-tert-butyl-4-methylphenol (BHT) and 2,2'-methylenebis(4-methyl-6-tert-butylphenol) (MBEBP) were individually dissolved at a concentration of 1% by volume in MB30 (30% moringa biodiesel with 70% diesel) fuel blend to investigate and compare NO as well as other emissions. The result shows that both antioxidants reduced NO emission significantly; however, HC, CO, and smoke were found slightly higher compared to pure biodiesel blends, but not more than the baseline fuel diesel. The result also shows that both antioxidants were quite effective in reducing peak heat release rate (HRR) and brake-specific fuel consumption (BSFC) as well as improving brake thermal efficiency (BTE) and oxidation stability. Based on this study, antioxidant-treated M. oleifera biodiesel blend (MB30) can be used as a very promising alternative source of fuel in diesel engine without any modifications.
One-time ultrasonication pre-treatment of Rhodobacter sphaeroides was evaluated for improving biohydrogen production via photofermentation. Batch experiments were performed by varying ultrasonication amplitude (15, 30, and 45%) and duration (5, 10, and 15 min) using combined effluents from palm oil as well as pulp and paper mill as a single substrate. Experimental data showed that ultrasonication at amplitude 30% for 10 min (256.33 J/mL) achieved the highest biohydrogen yield of 9.982 mL H2/mLmedium with 5.125% of light efficiency. A maximum CODtotal removal of 44.7% was also obtained. However, when higher ultrasonication energy inputs (>256.33 J/mL) were transmitted to the cells, biohydrogen production did not improve further. In fact, 20.6% decrease of biohydrogen yield (as compared to the highest biohydrogen yield) was observed using the most intense ultrasonicated inoculum (472.59 J/mL). Field emission scanning electron microscope images revealed the occurrence of cell damages and biomass losses if ultrasonication at 472.59 J/mL was used. The present results suggested that moderate ultrasonication pre-treatment was an effective technique to improve biohydrogen production performances of R. sphaeroides.
In dengue mosquitoes, successful embryonic development and long lifespan are key determinants for the persistence of both virus and vector. Therefore, targeting the egg stage and vector lifespan would be expected to have greater impacts than larvicides or adulticides, both strategies that have lost effectiveness due to the development of resistance. Therefore, there is now a pressing need to find novel chemical means of vector control. Coffee contains many chemicals, and its waste, which has become a growing environmental concern, is as rich in toxicants as the green coffee beans; these chemicals do not have a history of resistance in insects, but some are lost in the roasting process. We examined whether exposure to coffee during embryonic development could alter larval eclosion and lifespan of dengue vectors. A series of bioassays with different coffee forms and their residues indicated that larval eclosion responses of Aedes albopictus and Ae. aegypti were appreciably lower when embryonic maturation occurred in environments containing coffee, especially roasted coffee crude extract (RCC). In addition, the lifespan of adults derived from eggs that hatched successfully in a coffee milieu was reduced, but this effect was less pronounced with roasted and green coffee extracts (RCU and GCU, respectively). Taken together, these findings suggested that coffee and its residues have embryocidal activities with impacts that are carried over onto the adult lifespan of dengue vectors. These effects may significantly reduce the vectorial capacity of these insects. Reutilizing coffee waste in vector control may also represent a realistic solution to the issues associated with its pollution.
Open biomass burning in Peninsula Malaysia, Sumatra, and parts of the Indochinese region is a major source of transboundary haze pollution in the Southeast Asia. To study the influence of haze on rainwater chemistry, a short-term investigation was carried out during the occurrence of a severe haze episode from March to April 2014. Rainwater samples were collected after a prolonged drought and analyzed for heavy metals and major ion concentrations using inductively coupled plasma mass spectroscopy (ICP-MS) and ion chromatography (IC), respectively. The chemical composition and morphology of the solid particulates suspended in rainwater were examined using a scanning electron microscope coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). The dataset was further interpreted using enrichment factors (EF), statistical analysis, and a back trajectory (BT) model to find the possible sources of the particulates and pollutants. The results show a drop in rainwater pH from near neutral (pH 6.54) to acidic (
This study emphasizes on near surface observation of chemically active trace gases such as nitrogen dioxide (NO2) over Islamabad on a regular basis. Absorption spectroscopy using backscattered extraterrestrial light source technique was used to retrieve NO2 differential slant column densities (dSCDs). Mini multi-axis-differential optical absorption spectroscopy (MAX-DOAS) instrument was used to perform ground-based measurements at Institute of Environmental Sciences and Engineering (IESE), National University of Sciences and Technology (NUST) Islamabad, Pakistan. Tropospheric vertical column densities (VCDs) of NO2 were derived from measured dSCDs by using geometric air mass factor approach. A case study was conducted to identify the impact of different materials (glass, tinted glass, and acrylic sheet of various thicknesses used to cover the instrument) on the retrieval of dSCDs. Acrylic sheet of thickness 5 mm was found most viable option for casing material as it exhibited negligible impact in the visible wavelength range. Tropospheric NO2 VCD derived from ground-based mini MAX-DOAS measurements exceeded two times the Pak-NEQS levels and showed a reasonable comparison (r (2) = 0.65, r = 0.81) with satellite observations (root mean square bias of 39 %) over Islamabad, Pakistan.
In this study, the photocatalytic degradation of toxic pollutant (2-chlorophenol) in the presence of ZnO nanoparticles (ZnO NPs) was investigated under solar radiation. The three main factors, namely pH of solution, solar intensity and calcination temperature, were selected in order to examine their effects on the efficiency of the degradation process. The response surface methodology (RSM) technique based on D-optimal design was applied to optimise the process. ANOVA analysis showed that solar intensity and calcination temperature were the two significant factors for degradation efficiency. The optimum conditions in the model were solar intensity at 19.8 W/m(2), calcination temperature at 404 °C and pH of 6.0. The maximum degradation efficiency was predicted to be 90.5% which was in good agreement with the actual experimental value of 93.5%. The fit of the D-optimal design correlated very well with the experimental results with higher values of R (2) and R (2)adj correlation coefficients of 0.9847 and 0.9676, respectively. The intermediate mechanism behaviour of the 2-chlorophenol degradation process was determined by gas chromatography-mass spectrometry (GC-MS). The results confirmed that 2-chlorophenol was converted to acetic acid, a non-toxic compound.
This paper analyses empirically the optimal climate change mitigation policy of Malaysia with the business as usual scenario of ASEAN to compare their environmental and economic consequences over the period 2010-2110. A downscaling empirical dynamic model is constructed using a dual multidisciplinary framework combining economic, earth science, and ecological variables to analyse the long-run consequences. The model takes account of climatic variables, including carbon cycle, carbon emission, climatic damage, carbon control, carbon concentration, and temperature. The results indicate that without optimal climate policy and action, the cumulative cost of climate damage for Malaysia and ASEAN as a whole over the period 2010-2110 would be MYR40.1 trillion and MYR151.0 trillion, respectively. Under the optimal policy, the cumulative cost of climatic damage for Malaysia would fall to MYR5.3 trillion over the 100 years. Also, the additional economic output of Malaysia will rise from MYR2.1 billion in 2010 to MYR3.6 billion in 2050 and MYR5.5 billion in 2110 under the optimal climate change mitigation scenario. The additional economic output for ASEAN would fall from MYR8.1 billion in 2010 to MYR3.2 billion in 2050 before rising again slightly to MYR4.7 billion in 2110 in the business as usual ASEAN scenario.
Exploring new renewable energy sources as a substitute of petroleum reserves is necessary due to fulfilling the oncoming energy needs for industry and transportation systems. In this quest, a lot of research is going on to expose different kinds of new biodiesel sources. The non-edible oil from candlenut possesses the potential as a feedstock for biodiesel production. The present study aims to produce biodiesel from crude candlenut oil by using two-step transesterification process, and 10%, 20%, and 30% of biodiesel were mixed with diesel fuel as test blends for engine testing. Fourier transform infrared (FTIR) and gas chromatography (GC) were performed and analyzed to characterize the biodiesel. Also, the fuel properties of biodiesel and its blends were measured and compared with the specified standards. The thermal stability of the fuel blends was measured by thermogravimetric analysis (TGA) and differential scan calorimetry (DSC) analysis. Engine characteristics were measured in a Yanmar TF120M single cylinder direct injection (DI) diesel engine. Biodiesel produced from candlenut oil contained 15% free fatty acid (FFA), and two-step esterification and transesterification were used. FTIR and GC remarked the biodiesels' existing functional groups and fatty acid methyl ester (FAME) composition. The thermal analysis of the biodiesel blends certified about the blends' stability regarding thermal degradation, melting and crystallization temperature, oxidative temperature, and storage stability. The brake power (BP), brake specific fuel consumption (BSFC), and brake thermal efficiency (BTE) of the biodiesel blends decreased slightly with an increasing pattern of nitric oxide (NO) emission. However, the hydrocarbon (HC) and carbon monoxides (CO) of biodiesel blends were found decreased.
The focus of this study is to analyze the level of knowledge, awareness, and attitude toward plastic waste and to distinguish the key drivers that encourage the households in Kuala Lumpur, Malaysia, to participate in "No plastic campaign," This study used the logistic regression model to explain the factors that may affect the willingness to participate (WTP) of households in the campaign. In this study, it is found that 35 % of households are willing to participate in the campaign. The results of the study also indicate that people who are more informed and more convinced of their knowledge have a more positive attitude toward recycling than their counterparts do. Furthermore, this study provides additional evidence of the level and classification of importance of motivating factors for plastic recycling, using the modified average and coefficient of variation of the models. From the analysis, the factor "helps reduce landfill use" is found as the most important factor and the factor of "raising money for charity" is found as the least important factor that motivates households to participate in recycling. The determinations of the study suggest some strategies that could hold implications for government and households to boost them to participate in the campaign "No Plastic Bag."
Although a significant amount of brewery wastewater (BW) is generated during beer production, the nutrients in the BW could be reused as a potential bio-resource for biohydrogen production. Therefore, improvements in photofermentative biohydrogen production due to a combination of BW and pulp and paper mill effluent (PPME) as a mixed production medium were investigated comprehensively in this study. The experimental results showed that both the biohydrogen yield and the chemical oxygen demand removal were improved through the combination of BW and PPME. The best biohydrogen yield of 0.69 mol H2/L medium was obtained using the combination of 10 % BW + 90 % PPME (10B90P), while the reuse of the wastewater alone (100 % BW and 100 % PPME) resulted in 42.3 and 44.0 % less biohydrogen yields than the highest yield, respectively. The greatest light efficiency was 1.97 % and was also achieved using the combination of both wastewaters at 10B90P. This study revealed the potential of reusing and combining two different effluents together, in which the combination of BW and PPME improved the nutrients and light penetration into the mixed production medium.
Since bisphenol A (BPA) exhibits endocrine disrupting action and high toxicity in aqueous system, there are high demands to remove it completely. In this study, the BPA removal by sonophotocatalysis coupled with nano-structured graphitic carbon nitride (g-C3N4, GCN) was conducted with various batch tests using energy-based advanced oxidation process (AOP) based on ultrasound (US) and visible light (Vis-L). Results of batch tests indicated that GCN-based sonophotocatalysis (Vis-L/US) had higher rate constants than other AOPs and especially two times higher degradation rate than TiO2-based Vis-L/US. This result infers that GCN is effective in the catalytic activity in Vis-L/US since its surface can be activated by Vis-L to transport electrons from valence band (VB) for utilizing holes (h+VB) in the removal of BPA. In addition, US irradiation exfoliated the GCN effectively. The formation of BPA intermediates was investigated in detail by using high-performance liquid chromatography-mass spectrometry (HPLC/MS). The possible degradation pathway of BPA was proposed.
Benzo(a)pyrene degradation was compared in soil that was either composted, incubated at a constant temperature of 22 °C, or incubated under a temperature regime typical of a composting process. After 84 days, significantly more (61%) benzo(a)pyrene was removed from composted soil compared to soils incubated at a constant temperature (29%) or at composting temperatures (46%). Molecular fingerprinting approaches indicated that in composted soils, bacterial community changes were driven by both temperature and organic amendment, while fungal community changes were primarily driven by temperature. Next-generation sequencing data revealed that the bacterial community in composted soil was dominated by Actinobacteria (order Actinomycetales), Firmicutes (class Bacilli), and Proteobacteria (classes Gammaproteobacteria and Alphaproteobacteria), regardless of whether benzo(a)pyrene was present or not. The relative abundance of unclassified Actinomycetales (Actinobacteria) was significantly higher in composted soil when degradation was occurring, indicating a potential role for these organisms in benzo(a)pyrene metabolism. This study provides baseline data for employing straw-based composting strategies for the removal of high molecular weight PAHs from soil and contributes to the knowledge of how microbial communities respond to incubation conditions and pollutant degradation.
The environmental impacts with regard to agro-based biofuel production have been associated with the impact of greenhouse gas (GHG) emissions. In this study, field GHG emissions during plantation stage of palm oil-based biofuel production associated with land use changes for oil palm plantation development have been evaluated. Three different sites of different land use changes prior to oil palm plantation were chosen; converted land-use (large and small-scales) and logged-over forest. Field sampling for determination of soil N-mineralisation and soil organic carbon (SOC) was undertaken at the sites according to the age of palm, i.e. <5 years (immature), 5-20 and >21 years (mature oil palms). The field data were incorporated into the estimation of nitrous oxide (N2O) and the resulting CO2-eq emissions as well as for estimation of carbon stock changes. Irrespective of the land conversion scenarios, the nitrous oxide emissions were found in the range of 6.47-7.78 kg N2O-N/ha resulting in 498-590 kg CO2-eq/ha. On the other hand, the conversion of tropical forest into oil palm plantation has resulted in relatively higher GHG emissions (i.e. four times higher and carbon stock reduction by >50%) compared to converted land use (converted rubber plantation) for oil palm development. The conversion from previously rubber plantation into oil palm plantation would increase the carbon savings (20% in increase) thus sustaining the environmental benefits from the palm oil-based biofuel production.