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In aquatic environments, excessive amounts of inorganic nutrients, such as heavy metals, pose a metabolic risk and threaten to halt microbial activity. Metal-resistant bacteria, through various metabolic activities, can treat and detoxify harmful inorganic compounds. Thus, higher energy and electron transport system (ETS) demands may be necessary for metal bioremediation, but cell viability may be affected. Therefore, the metabolic respiration activity of cells in the presence of Cu, Zn, Ni, and Cr individually and in the quaternary is an important aspect of this study that relies on estimating the action of respiration enzymes responsible for metabolic activity and glucose reduction over periods of metallic stress and growth phases. Three species of bacteria, including B. megaterium, S. ginsenosidimutans, and K. rhizophila, were isolated from the electroplating effluent and used to determine the activity level of catalase, dehydrogenase enzymes, and glucose reduction. Their ability to sustain metabolic activity and understand their role in conferring tolerance and bioremediation capabilities to bacteria was evaluated. The findings revealed that metabolic activity was greater during the exponential phase than during the stationary phase. Catalase production was less affected by high metal levels; additionally, sugar reduction was improved but decreased with increased metal levels, and growth progressed, in comparison to dehydrogenase activity, which was more sensitive to high metal levels. Although respiratory metabolism activity decreased with increasing cell age and high metal concentrations, metabolism and viability persisted under metallic stress. This establishes the tolerability of bacteria and recommends them for potential bioremediation of metallic pollutants and environmental clean-up. [ABSTRACT FROM AUTHOR]

Biodegradation of used engine oil (UEO) that pollutes the environment is attracting increasing attention. The aim of this study was to characterize the adsorption of used engine oil (UEO) and the immobilization of UEO biodegraders in Ochrobacterium intermedium LMG 3301 and Ochrobacterium intermedium LMG 3301 plus Bacillus paramycoides MCCC1A04098 (BC) using alginate-attapulgite-calcium carbonate (AAC). Twenty AAC beads were tested separately in 20 mL of soil water extract (SWE) and hexane containing 1% UEO for their adsorptive capacities of UEO in 50-mL capped flasks. The results showed that the UEO removal efficiency (%RE) was bead-number dependent, recording a maximum of 83 ± 0.32% in SWE, and 11.50 ± 0.52% in hexane correlating with the highest number of AAC-granules (20 beads). The 1st order kinetics in SWE showed a UEO adsorption rate, K1 (h−1), of 0.11–0.15 h−1 correlating with 20 AAC-granules and 1, 2, 3 and 4% (w/v) UEO. The intra-particle diffusion kinetic model suggested that intra-diffusion was the main mode of mass transfer in AAC granules. The microscopic study and 2,3,5-triphenyltetrazolium chloride (TTC) positive stain showed that bacteria grew well in AAC. This result demonstrates that this matrix can be applied in the formulation of novel adsorptive granular formulas for bioremediation of UEO. [ABSTRACT FROM AUTHOR]

A consortium of bacteria capable of decomposing oily hydrocarbons was isolated from tarballs on the beaches of Terengganu, Malaysia, and classified as Pseudomonas stutzeri, Cellulosimicrobium cellulans, Acinetobacter baumannii and Pseudomonas balearica. The Taguchi design was used to optimize the biodegradation of diesel using these bacteria as a consortium. The highest biodegradation of diesel-oil in the experimental tests was 93.6%, and the individual n-alkanes decomposed 87.6—97.6% over 30 days. Optimal settings were inoculum size of 2.5 mL (1.248 OD600nm); 12% (v/v) the initial diesel-oil in a minimal salt medium of pH 7.0, 30.0 gL−1 NaCl and 2.0 gL−1 NH4NO3 concentration, incubated at 42 °C temperature and 150 rpm agitation speed. Parameters significantly improved diesel-oil removal by consortium as shown by the model determination coefficient (R2 = 90.89%; P < 0.001) with a synergistic effect of agitation speed significantly contributing 81.03%. Taguchi design determined the optimal settings for the parameters under study, which significantly improved diesel-oil removal by consortium. This can be used to design a novel bioremediation strategy that can achieve optimal decontamination of oil pollution in a shorter time. Highlights: Hydrocarbon-degraders in Tarball were isolated and identified by their 16S rRNA gene sequence as Pseudomonas stutzeri, Cellulosimicrobium cellulans, Acinetobacter baumanniiand Pseudomonas balearica. Taguchi method was applied to optimize effects of parameters such as initial diesel concentration, salinity (NaCl concentration), nitrate (NH4NO3) concentration, pH, temperature, agitation speed and inoculum size on diesel-oil removal in 30 days. Maximum diesel-oil biodegradation by experimental runs was 93.6% with individual n-alkanes degraded between 87.6% – 97.6% in 30 days Optimal settings were 2.5 mL (1.248 OD600nm) inoculum size; 12% (v/v) initial diesel-oil in MSM media with 7.0 pH, 30.0 gL−1 NaCl and 2.0 gL−1 NH4NO3 concentration, incubated at 42 °C temperature and 150 rpm agitation speed Parameters significantly improved diesel-oil removal by this consortium as indicated by model determination coefficient (R2 = 90.89%; P < 0.001) with synergistic effect of agitation speed significantly contributing 81.03% Taguchi design established optimal settings of investigated parameters that produced significant improvement on diesel-oil removal by consortium [ABSTRACT FROM AUTHOR]

The aim of this a pioneering research is to investigate linear alkylbenzenes (LABs) as biomarkers of sewage pollution in sediments collected from four rivers and estuaries of the south and east of Peninsular Malaysia. The sediment samples went through soxhlet extraction, two-step column chromatography purification, fractionation and gas chromatography–mass spectrometry (GC–MS) analysis. Principal component analysis (PCA) with multivariate linear regression (MLR) was used as well for source apportionment of LABs. The results of this study showed that total LAB concentration was 36–1196 ng g−1dw. The internal to external isomer ratios (I/E ratio) of LABs were from 0.56 to 3.12 indicated release of raw sewage and primary and secondary effluents into the environment of south and east of Peninsular Malaysia. Our research supported that continuous monitoring of sewage pollution to limit the environmental pollution in riverine and estuarine ecosystem. [ABSTRACT FROM AUTHOR]

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Oil spill introduces hydrocarbons into the marine environment and forms oil slicks, which aggregate with other debris to form tarballs. Tarballs are composed of toxic hydrocarbons, which persist in the environment, causing economic and ecological damages. This work studied the isolation and optimization of diesel-oil biodegradation by an indigenous bacterium, identified by 16S rRNA gene sequence analysis, in tarball. An experimental methodology using a Taguchi orthogonal array was applied to optimize the effects of diesel concentration, salinity, nitrate concentration, pH, temperature, agitation speed and time. An isolated bacterium identified as Cellulosimicrobium cellulans removed 88.4% of diesel oil under optimized conditions, where initial diesel-oil concentration was 5% (v/v), NaCl concentration was 20 gL-1 and NH4NO3 concentration was 2 gL-1 in Minimal Salt Media at pH 7, 40oC and 100 revolutions per minute for 5 days. Tarballs harbor hydrocarbon-degrading C. cellulans that can be used under optimized conditions to design an effective oil spill bioremediation technique for mitigating oil pollution. [ABSTRACT FROM AUTHOR]

Carbamates are poisonous pesticides which have been used widely in agriculture production for decades. Unlike other pesticides such as organophosphate, carbamate pesticides are not persistent in the environment however, their degradation is crucial due to their toxicity to living system. The World Health Organization, categorized carbamate pesticide as toxic, hazardous and restricted for use. Example of carbamates pesticides include Carbaryl, Aldicarb, Methomyl, Carbofuran, and Propoxur. They are extensively used to control many insect and pests of crops. Presently, there is signifcant awareness regarding the negative effects of pesticides due to their ability to pollute soil and water bodies. Most pesticides are readily degraded or metabolized by microbes. Carbamate pesticide degradation by microorganisms relies not only on the availability of microbes with suitable biodegradative enzymes, but also on the various ecological factors. This review- article outlines the present development in biodegradation of carbamate pesticides, their toxicity and enzymatic degradation as well as their degradative pathways. [ABSTRACT FROM AUTHOR]

There is no virtual report on the commercial cultivation of Arthrospira in Malaysia beyond the laboratory scale probably because of the high costs of production and the lower yield which are highly interconnected with the algal cultivation techniques. One way to alleviate the production cost is through outdoor mass cultivation under natural conditions using all available resources. Therefore, the present study was conducted to investigate the prospects of the production of Arthrospira platensis under Malaysian tropical climate using enhanced cultivation techniques to reach a maximum yield. In this study, the growth and yield of A. platensis were investigated under three different cultivation conditions: laboratory (control), outdoor shaded (greenhouse, T1), and outdoor non-shaded (field, T2). The algal growth was measured through optical density, biomass dry weight, and chlorophyll a content. The algal yield was determined by calculating its productivity and specific growth rate. The A. platensis cultivation under outdoor non-shaded conditions achieved significantly higher growth (p < 0.05) with 1.62 ± 0.038 ABS of maximum optical density, 0.88 ± 0.020 g L-1 of maximum biomass dry weight, 8.77 ± 0.219 mg L-1 of maximum chlorophyll a content, 0.091 ± 0.0022 g L-1 d-1 of productivity and 0.220 ± 0.0017 μ d-1 of specific growth rate over a cultivation period of eight days. The present finding showed that the Malaysian climate is suitable for a satisfactory A. platensis productivity with proper cultivation techniques such as the pre-adaptation of the algal culture, inoculation in the late evening, continuous agitation and compensation of the evaporated culture medium. [ABSTRACT FROM AUTHOR]

Abstract: Rapid increase in industrialization and urbanization in the west coast of Peninsular Malaysia has led to the intense release of petroleum and products of petroleum into the environment. Surface sediment samples were collected from the Selangor River in the west coast of Peninsular Malaysia during four climatic seasons and analyzed for PAHs and biomarkers (hopanes). Sediments were soxhlet extracted and further purified and fractionated through first and second step column chromatography. A gas chromatography-mass spectrometry (GC-MS) was used for analysis of PAHs and hopanes fractions. The average concentrations of total PAHs ranged from 219.7 to 672.3 ng g−1 dw. The highest concentrations of PAHs were detected at 964.7 ng g−1 dw in station S5 in the mouth of the Selangor River during the wet inter-monsoonal season. Both pyrogenic and petrogenic PAHs were detected in the sediments with a predominance of the former. The composition of hopanes was homogeneous showing that petroleum hydrocarbons share an identical source in the study area. Diagnostic ratios of hopanes indicated that some of the sediment samples carry the crankcase oil signature.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Background: Environmental policies should be developed in a contextual decision-making process regarding local environmental concerns emphasizing the economic, technical, social and institutional considerations. Establishing emission limit levels, especially in the industrial sector, is one of the most problematic environmental issues in developing countries, for which it is essential to include several criteria that reflect their country-specific constraints and capacities. Since Best Available Technology (BAT) is acknowledged to be the reference element for sustainable development and a basis for Emissions Limit Values (ELVs), the objective of this study is to present a reliable methodology for establishing ELVs thresholds with an emphasis on the BAT concept for national regulation at the sector level. Methods: A hybrid fuzzy multiple-criteria decision-making (FMCDM) process, consisting of the Analytic Hierarchy Process (AHP) and fuzzy Technique for Order of Preference by Similarity to Ideal Solution (fuzzy TOPSIS) method, is structured to aggregate the different criteria and rank different ELV alternatives in this complicated evaluation. In order to use the most profound knowledge and judgment of a professional expert team, this qualitative assessment highlights the importance of supportive information. Results: The results obtained indicate that experts have considered the country-specific information as a reliable reference in their decisions. Among different key evaluation criteria in effluent standard setting, the highest experts' priority is "Environmental protection". For both the conventional and toxic pollutants, the influence of all other criteria namely "Economic feasibility", "Technology viability" and "Institutional capacity", as constraining criteria in developing countries, have not reduced the responsibility towards the environmental objectives. In ELVs ranking, experts have made their decisions with respect to the specific characteristics of each pollutant and the existing capacities and constraints of the country, without emphasizing on any specific reference. Conclusions: This systematic and transparent approach has resulted in defensible country-specific ELVs for the Iron and Steel industry, which can be developed for other sectors. As the main conclusion, this paper demonstrates that FMCDM is a robust tool for this comprehensive assessment especially regarding the data availability limitations in developing countries. [ABSTRACT FROM AUTHOR]

Passive bioremediation of metal- and sulfate-containing acid mine drainage (AMD) has been investigated in a batch study. Multiple substrates were used in the AMD remediation using spent mushroom compost (SMC), limestone, activated sludge (AS), and woodchips (WC) under anoxic conditions suitable for bacterial sulfate reduction (BSR). Limestones used were of crushed limestone (CLS) and uncrushed limestone, provided at two different ratios in mixed substrates treatment and varied by the proportion of SMC and limestone. The SMC greatly assisted the removals of sulfate and metals and also acted as an essential carbon source for BSR. The mixed substrate composed of 40% CLS, 30% SMC, 20% AS, and 10% WC was found to be effective for metal removal. Mn, Cu, Pb, and Zn were greatly removed (89–100%) in the mixed substrates treatment, while Fe was only removed at 65%. Mn was found to be removed at a greatly higher rate than Fe, suggesting important Mn adsorption onto organic materials, that is, greater sorption affinity to the SMC. Complementary with multiple treatment media was the main mechanism assisting the AMD treatment through microbial metal reduction reactions. [ABSTRACT FROM AUTHOR]

This is the first extensive report on linear alkylbenzenes (LABs) as sewage molecular markers in surface sediments collected from the Perlis, Kedah, Merbok, Prai, and Perak Rivers and Estuaries in the west of Peninsular Malaysia. Sediment samples were extracted, fractionated, and analyzed using gas chromatography mass spectrometry (GC-MS). The concentrations of total LABs ranged from 68 to 154 (Perlis River), 103 to 314 (Kedah River), 242 to 1062 (Merbok River), 1985 to 2910 (Prai River), and 217 to 329 ng g (Perak River) dry weight (dw). The highest levels of LABs were found at PI3 (Prai Estuary) due to the rapid industrialization and population growth in this region, while the lowest concentrations of LABs were found at PS1 (upstream of Perlis River). The LABs ratio of internal to external isomers (I/E) in this study ranged from 0.56 at KH1 (upstream of Kedah River) to 1.35 at MK3 (Merbok Estuary) indicating that the rivers receive raw sewage and primary treatment effluents in the study area. In general, the results of this paper highlighted the necessity of continuation of water treatment system improvement in Malaysia. [ABSTRACT FROM AUTHOR]

The current study is one of the first studies evaluating the levels of linear alkylbenzenes (LABs) in surface sediments of Sarawak and Sembulan rivers which are located in the east coast of Malaysia. The LABs, which are molecular tracers of sewage contamination, were measured in 15 surface sediment samples collected from these rivers. The samples were extracted, fractioned and analyzed by gas chromatography mass spectrometry (GC-MS). The findings revealed that the concentrations of ΣLABs ranged from 156.47 to 7386.19 ng/g dry weight (dw) in the sediments of Sarawak River and from 643.18 to 5567.12 ng/g dw in the sediments of Sembulan River. The highest LABs levels were detected in the sediments collected from the sampling location SS9 in Sembulan River whereas the lowest levels were observed in the SS1 sampling location in Sarawak River. The I/E ratios (ratio of internal to external isomers of LABs) for Sarawak River sediments ranged from 0.52 to 0.98 while for Sembulan River they fell within the range 0.87-1.79. The I/E ratio at the sampling station SS4 was much lower than the I/E ratios at the other stations, thus indicating that the wastewater discharged into Sarawak River from the areas surrounding station SS4 was poorly treated. [ABSTRACT FROM AUTHOR]

Extensive use of carbofuran insecticide harms the environment and human health. Carbofuran is an endocrine disruptor and has the highest acute toxicity to humans than all groups of carbamate pesticides used. Carbofuran is highly mobile in soil and soluble in water with a lengthy half-life (50 days). Therefore, it has the potential to contaminate groundwater and nearby water bodies after rainfall events. A bacterial strain BRC05 was isolated from agricultural soil characterized and presumptively identified as Enterobacter sp. The strain was immobilized using gellan gum as an entrapment material. The effect of different heavy metals and the ability of the immobilized cells to degrade carbofuran were compared with their free cell counterparts. The results showed a significant increase in the degradation of carbofuran by immobilized cells compared with freely suspended cells. Carbofuran was completely degraded within 9 h by immobilized cells at 50 mg/L, while it took 12 h for free cells to degrade carbofuran at the same concentration. Besides, the immobilized cells completely degraded carbofuran within 38 h at 100 mg/L. On the other hand, free cells degraded the compound in 68 h. The viability of the freely suspended cell and degradation efficiency was inhibited at a concentration greater than 100 mg/L. Whereas, the immobilized cells almost completely degraded carbofuran at 100 mg/L. At 250 mg/L concentration, the rate of degradation decreased significantly in free cells. The immobilized cells could also be reused for about nine cycles without losing their degradation activity. Hence, the gellan gum-immobilized cells of Enterobacter sp. could be potentially used in the bioremediation of carbofuran in contaminated soil. [ABSTRACT FROM AUTHOR]