Showing papers by "Mohd Izuan Effendi Halmi published in 2019"

Artificial Neural Networks (ANNs) and Response Surface Methodology (RSM) Approach for Modelling the Optimization of Chromium (VI) Reduction by Newly Isolated Acinetobacter radioresistens Strain NS-MIE from Agricultural Soil.

Abstract: Numerous technologies and approaches have been used in the past few decades to remove hexavalent chromium (Cr[VI]) in wastewater and the environment. However, these conventional technologies are not economical and efficient in removing Cr(VI) at a very low concentration (1-100 ppm). As an alternative, the utilization of bioremediation techniques which uses the potential of microorganisms could represent an effective technique for the detoxification of Cr(VI). In this study, we reported a newly isolated bacterium identified as Acinetobacter radioresistens sp. NS-MIE from Malaysian agricultural soil. The chromate reduction potential of strain NS-MIE was optimized using RSM and ANN techniques. The optimum condition predicted by RSM for the bacterium to reduce hexavalent chromium occurred at pH 6, 10 g/L ppm of nutrient broth (NB) concentration and 100 ppm of chromate concentration while the optimum condition predicted by ANN is at pH 6 and 10 g/L of NB concentration and of 60 ppm of chromate concentration with chromate reduction (%) of 75.13 % and 96.27 %, respectively. The analysis by the ANN model shows better prediction data with a higher R2 value of 0.9991 and smaller average absolute deviation (AAD) and root mean square error (RMSE) of 0.33 % and 0.302 %, respectively. Validation analysis showed the predicted values by RSM and ANN were close to the validation values, whereas the ANN showed the lowest deviation, 2.57%, compared to the RSM. This finding suggests that the ANN showed a better prediction and fitting ability compared to the RSM for the nonlinear regression analysis. Based on this study, A. radioresistens sp. NS-MIE exhibits strong potential characteristics as a candidate for the bioremediation of hexavalent chromium in the environment.

Optimization of an Ultrasound-Assisted Extraction Condition for Flavonoid Compounds from Cocoa Shells (Theobroma cacao) Using Response Surface Methodology

Abstract: This study investigates the ultrasound-assisted extraction of flavonoids from Malaysian cocoa shell extracts, and optimization using response surface methodology. There are three variables involved in this study, namely: ethanol concentration (70–90 v/v %), temperature (45–65 °C), and ultrasound irradiation time (30–60 min). All of the data were collected and analyzed for variance (ANOVA). The coefficient of determination (R2) and the model was significant in interaction between all variables (98% and p 0.0684. The ethanol concentration, temperature, and ultrasound irradiation time that yielded the maximum value of the total flavonoid content (TFC; 7.47 mg RE/g dried weight (DW)) was 80%, 55 °C, and 45 min, respectively. The optimum value from the validation of the experimental TFC was 7.23 ± 0.15 mg of rutin, equivalent per gram of extract with ethanol concentration, temperature, and ultrasound irradiation time values of 74.20%, 49.99 °C, and 42.82 min, respectively. While the modelled equation fits the data, the T-test is not significant, suggesting that the experimental values agree with those predicted by the response surface methodology models.

Simultaneous bioaccumulation and translocation of iron and aluminium from mining wastewater by Scirpus grossus

Abstract: Iron (Fe) and aluminium (Al) contamination due to mining activities has increased considerably and became a serious environmental problem. Phytoremediation is an emerging green technology that uses plants to treat heavy metal contaminated environment. In this study, Scirpus grossus was exposed to synthetic mining wastewater (binary mixture of Fe and Al with a mass ratio of 3:1) to assess its ability to phytoremediate Fe and Al with different treatment concentrations (90 mg/L Fe + 30 mg/L Al – 450 mg/L Fe + 150 mg/L Al). The plants were exposed for 102 d in a subsurface batch system. The results show that the S. grossus accumulated Fe and Al simultaneously in biomass throughout the study. The maximum accumulations of Fe and Al were found on Day 42 in the plant roots (50,277 mg/kg Fe in 450 mg/L Fe + 150 mg/L Al treatment and 7,744 mg/kg Al in 300 mg/L Fe + 100 mg/L Al treatment). The bioaccumulation factor and translocation factor of S. grossus were found to be greater than 1 and less than 1, respectively, for the two metals, indicating that this species is a hyperaccumulator that uses phytostabilization in the phytoremediation of Fe and Al.

Lipase-catalyzed synthesis of red pitaya (Hylocereus polyrhizus) seed oil esters for cosmeceutical applications: process optimization using response surface methodology

Abstract: Esters were synthesized via the alcoholysis of red pitaya seed oil with oleyl alcohol catalyzed by immobilized lipase, Lipozyme RM IM. The effects of synthesis parameters, including temperature, time, substrate molar ratio and enzyme loading, on the yield and productivity of esters were assessed using a central composite response surface design. The optimum yield and productivity were predicted to be about 80.00% and 0.58 mmol h−1, respectively, at a synthesis temperature of 50.5 °C, time of 4 h, substrate molar ratio of 3.4 : 1 and with 0.17 g of enzyme. Esters were synthesized under the optimum synthesis conditions; it was found that the average yield and productivity were 82.48 ± 4.57% and 0.62 ± 0.04 mmol h−1, respectively, revealing good correspondence with the predicted values. The main esters were oleyl linoleate, oleyl oleate, oleyl palmitate and oleyl stearate. The synthesized esters exhibited no irritancy effects and their physicochemical properties showed their suitability for use as cosmeceutical ingredients.

Kinetic Analysis of the Adsorption of Glyphosate onto Palm Oil Fronds Activated Carbon

Abstract: Existing techniques for the treatment of pollutants include membrane separation, ion exchange, precipitation, transformation and biosorption. Of all of this technology, biosorption has several positive aspects which include low operating expenses, very efficient detoxification of toxicants at low concentrations, low amount of disposal materials and does not need nutrient requirements as in bacterial-based remediation, the latter of which is limited by the presence of heavy metals and other toxicants. The biosorption of glyphosate on palm oil fronds activated carbon can be an efficient and low-cost tool for remediation of glyphosate. The absorption kinetics data of biosorption isotherm on the biosorption of glyphosate on palm oil fronds activated carbon were analyzed using three models—pseudo-1st, pseudo-2nd and Elovich, and fitted using non-linear regression. The Elovich model was the poorest in fitting the curve based on visual observation followed by the pseudo-1st order. Statistical analysis based on root-mean-square error (RMSE), adjusted coefficient of determination (adjR2), bias factor (BF), accuracy factor (AF), corrected AICc (Akaike Information Criterion), Bayesian Information Criterion (BIC) and Hannan–Quinn information criterion (HQC) that showed that the pseudo-second order model is the best model. Kinetic analysis using the pseudo-second order model at 250 mg/L glyphosate gave a value of equilibrium sorption capacity qe of 94.12 mg g-1 (95% confidence interval from 89.913 to 98.332) and a value of the pseudo-second-order rate constant, k2 of 0.02 (95% confidence interval from 0.012 to 0.023). Further analysis is needed to provide proof for the chemisorption mechanism usually tied to this kinetic.

Assessment of heavy metal toxicity using a luminescent bacterial test based on Photobacterium sp. strain MIE

Abstract: Toxicity evaluation of wastewater, polluted sediment and water streams is a very crucial aspect of environmental pollution monitoring. In this work, a newly developed luminescent bacterial test using a tropical luminescent bacterium, Photobacterium sp. strain MIE was used to assess the toxicity of several heavy metals using a 15-min assay format. The assessment was carried out by exposing strain MIE to different concentrations of heavy metals ranging from 0.001 to 200 mg/L in a DTX microplate 96 wells. The toxicity result based on the inhibitory concentration (IC50) was Hg (0.053 mg/L) > Ag (0.12 mg/L) > Cu (0.85 mg/L) > Ni (12.32 mg/L) > Zn (18.72 mg/L) > Cr (26.02 mg/L). Principal Component Analysis (PCA) and Agglomerative Hierarchical Clustering (AHC) analyses showed the sensitivity (IC50) of strain MIE to several toxic heavy metals are comparable to the commercial luminescent assay, Microtox™ as both clusters together making it a good choice for an alternative near-real-time monitoring of heavy metals. The sensitivity of strain MIE towards heavy metals was proven through field trial works on several heavy metal-polluted sites in Malaysia. Thus, it is a good candidate as an early detection system for heavy metals in aquatic bodies in tropical countries.

Isothermal Modelling of the Adsorption of Glyphosate onto Palm Oil Fronds Activated Carbon

Abstract: Glyphosate is a heavily usage herbicide in Malaysia. It inhibits amino acids synthesis in plants and microorganisms with the latter inhibition makes it difficult to find biodegradation microorganism as a bioremediation agent for this pesticide. One candidate for bioremediation is biosorption that has several positive aspects which include low operating expenses, very efficient detoxification of toxicants at low concentrations, low amount of disposal materials and does not need nutrient requirements as in bacterial-based remediation, the latter of which is limited by the presence of heavy metals and other toxicants. The biosorption of glyphosate on palm oil fronds activated carbon can be an efficient and low-cost tool for remediation of glyphosate. The absorption kinetics data of biosorption isotherm on the biosorption of glyphosate on oil palm fronds activated carbon were analyzed using modelled according to various models ranging from one to five parameters models such as Henry, Langmuir, Dubinin-Radushkevich, Freundlich, BET, Toth, Sips, Fritz-Schlunder IV, Baudu and Fritz-Schlunder V, and fitted using non-linear regression. Only the Henry, Langmuir, Freundlich, BET and Toth models can fit the data. Statistical analysis based on root-mean-square error (RMSE), adjusted coefficient of determination (adjR2), bias factor (BF), accuracy factor (AF), corrected AICc (Akaike Information Criterion) showed that the Langmuir model is the best model. The calculated Langmuir parameters bL value of 0.002 L/mg (95% confidence interval from 0.001 to 0.004) and qmL value of 255.5 mg/g (95% confidence interval from 160.90 to 350.11).

Modelling the Effect of Heavy Metal on the Growth Rate of an SDS-degrading Pseudomonas sp. strain DRY15 from Antarctic soil

Abstract: The SDS-degrading bacterium Pseudomonas sp. strain DRY15 was strongly inhibited by heavy metals especially mercury. Growth of the SDS-degrading bacterium at various concentrations of mercury shows a sigmoidal pattern with lag periods ranging from 7 to 10 h. As the concentration of mercury was increased, the overall growth was inhibited with 1.0 g/L causing an almost cessation of bacterial growth. The modified Gompertz model was utilized to obtain growth rates at different concentrations of mercury. The growth rates obtained from the modified Gompertz model was then modelled according to the modified Han-Levenspiel, Wang, Liu, modified Andrews, the Amor and Shukor models. Out of the five models, only the Shukor, Wang, modified Han-Levenspiel and the Liu models were able to fit the curve, whilst the modified Andrews and Amor models were unable to fit the curves. The best model was Shukor based on the lowest values for RMSE and AICc, highest adjusted correlation coefficient (adR2) and values of AF and BF closest to unity. The parameters obtained from the Shukor model, which are Sm, max and n which represent critical heavy metal ion concentration (mg/L), maximum growth rate (h-1) and empirical constant values were 6.0 (95%, confidence interval from 5.87 to 6.14), 0.09 (95%, confidence interval of 0.086 to 0.096) and 4.2 (95%, confidence interval from 3.1 to 5.2), respectively.

Characterization of Antioxidant Activities in Red Dragon Fruit (Hylocereus polyrhizus) Pulp Water-based Extract

Abstract: The red dragon fruit, Hylocereus polyrhizus, locally known as Buah Naga has become increasingly popular among consumers and growers worldwide due to its antioxidative properties. The present study was conducted to examine the total phenolic content, total flavonoid content and antioxidant activities of water extract from fruit pulp of the species. The antioxidant activities were measured by DPPH (2,2-Diphenyl-1- picrylhydrazyl), ABTS (2-2’-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid), FRAP (Ferric Ion Antioxidant Power) and Phosphomolybdate assays. The total phenolic and flavonoid contents of pulp were recorded at 32.9 ± 0.92 mg GAE/100 mL and 2.26 ± 0.14 mg QE/100 mL of juice, respectively. The antioxidant or free radical scavenging activity, measured by the DPPH and ABTS protocols were 73.38 ± 2.24 % and 92.66 ± 0.22 %, respectively. The antioxidant capacity, determined by FRAP and Phosphomolybdate assays were 132.17 ± 3.74 µmol Fe2+/100 ml and 28.94 ± 0.83 mg AAE/100 mL of juice, respectively. The total phenolic and total flavonoid content in water extracts of pulp showed positively high correlations with DPPH, ABTS, FRAP and Phosphomolybdate assays. The results suggest that water, which is biodegradable and non-toxic, can be utilized to effectively extract active compounds in red dragon fruit pulp.

Resistance of native bacteria isolated from activated sludge towards iron and manganese

Abstract: A study was conducted to observe the resistance of native isolated bacteria towards selected heavy metals (iron; Fe and manganese; Mn) in a separate exposure. Isolated bacteria were evaluated by culturing them in nutrient broth medium that contained approximately 3 ×10⁶CFU/mL bacteria with different initial concentrations (0, 50, 100 and 200 mg/L). Result showed that a plate with bacterial growth indicated bacterial resistance, which was verified based on CFU/mL. At 0 mg/L, bacteria grew well on the plate with Fe and Mn. The bacterial number began to decrease at 50 and 100 mg/L for Fe and at 200 mg/L for Mn. Only a few colonies survived (isolate AM2) the toxicity of highFe amount; the isolated bacteria almost showed no growth along the plate. AM2, AM3 and AM4 presented resistance to Mn until 200 mg/L, but not AM6. The bacteria showed no growth at 100 and 200 mg/L. Thus, the Fe and Mn concentrations that can be applied during acclimatisation ranged from 0 mg/L to 200 mg/L with isolated AM2 and AM4 for Fe and Mn removal.

Kinetic Analysis of the Adsorption of the Brominated Flame Retardant 4-bromodiphenyl Ether onto Biochar-immobilized Sphingomonas sp.

Abstract: 4-bromophenyl phenyl ether or 4-bromodiphenyl ether (4-BDE) is a less brominated PBDE, which are brominated flame retardants (BFRs), that has come into importance when it was detected as the main pollutant in Sungai Buah, a tributary to the Sungai Semenyih that have recently caused the pollution of drinking waters in the Semenyih Water Treatment Plant, Putrajaya Selangor that led to water shortage for many days to affecting many areas. 4-BDE is also a recalcitrant priority pollutant where it is barely degraded at all. Many of the PBDE can cause developmental neurotoxicity. The absorption kinetics data of biosorption isotherm on the biosorption of 4-BDE onto Biochar-immobilized Sphingomonas sp. were analyzed using three models—pseudo-1st, pseudo-2nd and Elovich, and fitted using non-linear regression. The Elovich model was the poorest in fitting the curve based on visual observation followed by the pseudo-1st order. Statistical analysis based on root-mean-square error (RMSE), adjusted coefficient of determination (adjR2), bias factor (BF), accuracy factor (AF), corrected AICc (Akaike Information Criterion), Bayesian Information Criterion (BIC) and Hannan–Quinn information criterion (HQC) that showed that the pseudo-1ST order model is the best model. Kinetic analysis using the pseudo-1st order model at 400 mg/L 4-BDE gave a value of equilibrium sorption capacity qe of 31.89 mg g-1 (95% confidence interval from 30.37 to 33.42) and a value of the pseudo-1st-order rate constant, k1 of 0.22 (95% confidence interval from 0.019 to 0.025). Further analysis is needed to provide proof for the chemisorption mechanism usually tied to this kinetic.