Screening of culture conditions for production of xylanase from landfill soil bacteria

Xylan is a major constituent of hemicellulosic polysaccharides found in plant’s cell wall which represent up to 20-30% of the total dry weight in tropical plant biomass [1]. Besides, 9-12% of municipal solid waste are composed of hemicellulose on dry weight basis [2]. Enzymatic method can be used for the degradation of these materials involving the use of microbial enzymes [3] that are less polluting, environmental friendly, energy saving and lower disposal problems [4]. Xylanase is a biocatalyst which specifically degrade xylan into smaller sugars such as xylose and xylobiose [5]. It has been used in many important industrial applications such as pulp, paper, bakery, juice and beer industries [6]. This enzyme has been employed in paper manufacturing to bleach paper pulp and increase the brightness of paper pulp instead of using toxic and expensive chemicals [5]. Xylanase also being used in biofuel production such as ethanol from lignocellulose biomass and used in treatment of barley and wheat to improve the properties of animal diet in animal feed industries [1]. Besides, this enzyme can be applied for conversion of xylan into xylose in agricultural wastewater and to clarify fruit juices in beverage industries [7]. Microbes are prefer by the industries to produce various enzymes, because of high growth rate and large volume of enzymes can be obtained within a short time [8]. Employing microbes such as bacteria, yeast and filamentous fungi, that are known for their ability to secrete extracellular enzymes into the environment, may help to overcome the current challenge in reducing the volume of waste in landfill by biological conversion of municipal solid waste into bioenergy [9]

Comparison of graphene oxide properties synthesized by electrochemical exfoliation and hummers’ method

Graphene oxide (GO) is one of the nanoscales materials that have a unique property thus exhibit great potential applications in various field. However, to synthesize high- quality GO, environment- friendly and fast production rate is a huge challenge that needs to overcome. Although chemical synthesis method is the easiest, inexpensive, and high amount production rate as compared to the other methods but there are some drawbacks using chemicals such as toxicity, poisonous and corrosive which are harmful to the human health and environment. Therefore, researchers suggested a green route as an alternative method. This study compares the dissimilarities in properties such as morphologies, presence of functional groups and crystallization of GO synthesized by using electrochemical exfoliation method and the improved Hummers’ method. This research delivers a useful guideline to compare the effectiveness of both methods to benefit researchers who keen to synthesize GO. It also discussed the characterization results of GO using of X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy Dispersive X-Ray (EDX) and Fourier transform infrared spectroscopy (FTIR)

Synergistic syngas production: Needleless electrospinning synthesis of Co/CeO2–La2O3 catalyst for efficient dry reforming of methane

The prime cause for catalyst deactivation during dry reforming of methane (DRM) has been attributed to the deposition of carbon. Nanofibrous (NF) catalysts are attractive candidates that offer high catalytic activity and stability in DRM. A comparative study between electrospun and impregnated Co/CeO2–La2O3 catalysts in the DRM reaction was carried out to evaluate the merits of the NF catalyst. Application of the electrospun catalyst yielded the highest activity in DRM and showed a substantial improvement in resistance to carbon formation. The unique structure of the NF electrospun catalyst, the robust metal-support interaction, and the increased surface area could more effectively suppress deactivation of the catalyst during an 8-h DRM reaction than the impregnated catalyst

Optimization of syngas production via methane bi-reforming using CeO2 promoted Cu/MnO2 catalyst

Currently, syngas plays an important role in renewable and sustainable energy production. The idea of manufacturing syngas via bi-reforming methane, which involves the combination of methane (CH4), carbon dioxide (CO2), and steam, appears very promising. As a result, the goal of this research is to improve syngas output by improving process parameters in methane bi-reforming using a 3%Ce-15%Cu/MnO2 catalyst. Optimization analysis was performed using response surface methodology (RSM). The ultrasonic impregnation (UI) method was employed to synthesize the catalysts used in this study. Following that, the catalyst was characterized using several techniques such as Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD), and temperature programmed oxidation (TPO). The findings of the characterization show that the presence of CeO2 promoters has a dual effect on the size of CuO crystallites. Firstly, it reduces the size from 19.07 nm to 13.66 nm because to the dilutive effect generated by the inclusion of CeO2. Second, the presence of CeO2 promoter accelerates the transition from CuO to Cu0 metallic phase. Furthermore, the addition of CeO2 boosts the CH4 and CO2 conversion rates by 23.65% and 24.93%, respectively. As a result, the H2 yield increases significantly when compared to the unpromoted catalyst. The study investigates the influence of process parameters, specifically the reaction temperature (700–900℃), CO2 ratio (0.2–1), and gas hourly space velocity (GHSV) (16–36 L g cat−1 hr−1), on the conversion of CH4 and CO2, as well as the H2/CO ratio. The optimization study finds that the highest conversion rates for CH4 and CO2 are 78.32% and 72.45%, respectively, when the reaction temperature is 800 °C, the CO2 ratio is 0.6, and the gas hourly space velocity (GHSV) is 26 L g cat−1 hr−1. The optimum conditions result in the highest syngas ratio of 1.77. The results of the optimization are then assessed using the mean errors. The H2/CO ratio, as well as the average errors for CH4 and CO2 conversions, are discovered to be 0.15%, 0.95%, and 0%, respectively

Deciphering the imperative role of ruthenium in enhancing the performance of Ni/Nd2O3.Gd2O3 in glycerol dry reforming

Glycerol dry reforming (GDR) turns glycerol and CO2 into valuable syngas. The present work aims to decipher the imperative role of Ru metal in enhancing the performance of Ni/Nd2O3.Gd2O3 in GDR. The unpromoted 15%Ni/Nd2O3.Gd2O3 and promoted 3%Ru-Ni/Nd2O3.Gd2O3 catalysts are synthesized via the ultrasonic-assisted impregnation method while XRD, FESEM-EDX, H2-TPR and CO2-TPD analyses are used to characterize the catalysts. In this study, the influence of reaction variables such as temperature and the CO2 to glycerol ratio (CGR) was investigated. In accordance with XRD and FESEM-EDX analyses, the promoted catalyst exhibited a more refined morphology and more uniform Ni dispersion than the unpromoted catalyst. From the reaction study, the promoted 3%Ru-15%Ni/Nd2O3.Gd2O3 gives higher glycerol conversion (91%), H2 yield (65%) and CO yield (80%) at a reaction temperature of 800 °C and CGR of 1. This is due to the higher number of available active sites as well as the excellent diffusion of Ni metal across the surface of the catalyst. However, as Ni metal is susceptible to carbon formation and is easily sintered, the production of carbon is unavoidable for the catalysts. The XRD and TPO analyses shown that the addition of Ru reduces the amount of carbon that accumulates on the site of the catalyst, which in turn reduces the rate of deactivation

Syngas production from glycerol dry reforming using Nd2RuO5 perovskite catalysts

Currently, fossil fuels as the global energy sources have become a liability due to the emission of greenhouse gases that causes global temperature elevated and climate changes to happen more frequently. As a result, glycerol dry reforming (GDR) has been a research priority, owing to its reforming capabilities in turning greenhouse gases (CO2) and biodiesel byproducts (glycerol) into syngas. The choice of catalysts is critical for increasing the efficiency of the syngas production process. Hence, this paper studies the application of Nd2RuO5 perovskite catalysts on the dry reforming of glycerol. Before characterization, the catalysts were prepared by using the Pechini Sol-Gel method. GDR reactions were conducted using a fixed-bed reactor at operating conditions; 873 – 1173 K and CO2 to Glycerol ratio (CGR) at 1:1. Based on XRD finding, the dominant phase belongs to Nd2RuO5, a pseudo double perovskite. The reduction profile from TPR showed a lowered reduction temperature which belongs to Ru that reduced into Ru0. The images of perovskite showed a well dispersed and smooth surface, and no agglomeration occurred on the pore sites. From the catalytic evaluation on the effect of temperature, the best temperature was observed at 1073 K, giving the highest glycerol conversion at 69%, whereas for H2, CO yields 20.8% and 13.8%, respectively. Intense carbon formation has been detected at post XRD analysis which later confirmed to be a filamentous type, that oxidized at low oxidation temperature from 400 – 500 K

Isolation of solubilizing microorganisms from landfill soil

characterization and screening of cellulolytic and xylanolytic microorganisms from landfill soil and quantification of their enzymatic activity. Sample was collected from landfill soil of landfill site at Sg. Ikan, Kuala Terengganu, Malaysia. Isolation of the solubilizing microorganism was conducted via standard serial dilution and spread plate method using nutrient agar medium and these microorganisms were further characterized by morphological characteristics and Gram-staining. Screening tests demonstrated the ability of microorganism to produce cellulase and xylanase enzyme via Gram’s iodine-staining. Finally, selected isolates were subjected to enzyme activity quantification such as total cellulase, endoglucanase, exoglucanase and xylanase assay analysis. A total of 58 different isolates were isolated from landfill soil which Gram-positive bacilli were the dominant microorganism. Out of 58 isolates, 29 isolates were selected for further testing. After Gram’s iodine staining, there were 23 cellulolytic microorganisms and 26 xylanolytic microorganisms which showed clear zones on agar plate containing carboxymethyl cellulose and xylan, respectively. Two isolates out of 23 cellulolytic microorganisms and three isolates out of 26 xylanolytic microorganisms with ratio of clear zone (D/d) more than 3.3 were furthered tested for quantification of enzyme activity. Cellulolytic microorganism M12 had the highest endoglucanase activity at 1.7621±0.0054 U/mL while cellulolytic microorganism M28 had the highest total cellulase activity and exoglucanase activity at 1.6086±0.0007 U/mL and 1.8299±0.0704 U/mL, respectively. Meanwhile, xylanolytic microorganism M15 had the highest xylanase activity at 8235±0.1715 U/mL. In conclusion, the 58 microorganisms were isolated which initiated research on industrially important microorganism from landfill soil and these isolates may be vital source for the discovery of industrial useful enzymes especially in municipal solid waste degradation

Factorial experimental design for xylanase production by Bacillus sp. isolated from Malaysia landfill soil

Two-level full factorial design was applied to screen the important parameters for production of xylanase by newly isolated Bacillus sp. from landfill soil. Five production parameters were considered: initial pH media (pH 5–9), inoculum size (5%–10% v/v), incubation period (18–30 h), temperature (30-50 °C) and agitation speed (0-200 rpm). Xylanase activity was estimated using dinitrosalicylic acid (DNS) based on the xylose released under specified assay conditions. Based on the factorial analysis, it was observed that the significant parameters in the xylanase production were temperature, agitation speed and initial pH of media. Meanwhile, the interaction between temperature and initial pH of media gave the highest influenced to the xylanase production. The model revealed that the highest xylanase activity can be achieved at 123.34 U/mL with initial pH media of 7.0, 30 h incubation period, 5% (v/v) inoculum size, agitation speed of 100 rpm at 40 °C. Confirmation run produced the highest experimental xylanase activity by Bacillus sp. at 123.10 U/mL with 0.17% of error than the predicted one. Hence, the model was reliably predicting the xylanase production

Screening of Culture Conditions for Production of Xylanase from Landfill Soil Bacteria

Culture conditions including initial pH media, incubation period, inoculum size, type of carbon source, type of nitrogen source and its concentration, which affect xylanase production were screened via the one-factor-at-a-time approach. The bacteria used in the production of xylanase was isolated from the landfill site at Sg. Ikan, Kuala Terengganu, Malaysia. Three characterizations of the landfill soil were investigated for their moisture content, ash content, and pH. The culture conditions range used in the experimental work were between 6–30 h for the incubation period, with initial pH between 5–9, inoculum size between 1–20% v/v, carbon, nitrogen sources, and nitrogen source concentration between 1–5% w/v. Xylanase activity was estimated using dinitrosalicylic acid (DNS) based on the release of xylose under standard assay conditions. The landfill soil was observed to have pH between pH 3.4–7.2 with a moisture content between 12.4–33.7% and ash ranged between 3.5–4.3%. Results showed that the highest xylanase activity within studied ranges was recorded at 25.91±0.0641 U/mL with 10% (v/v) inoculum size, 1% (w/v) xylose as sole carbon source, mixture of 1% (w/v) peptone and 0.25% (w/v) ammonium sulphate as nitrogen sources, which was carried out at initial pH of 8.0 for 24 h incubation

The effect of oxygen mobility/vacancy on carbon gasification in nano catalytic dry reforming of methane: A review

Dry reforming of methane (DRM) remains challenging due to catalyst deactivation driven primarily by carbon deposition and metal sintering. Nanocatalytic materials offer great activity and stability in the DRM reaction due to the high dispersion of ultrasmall metal nanoparticles. Here we present a designated review on the role of the catalyst’s oxygen mobility/vacancy in carbon gasification during the DRM reaction. The presence of mobile oxygen and/or oxygen vacancy in nanocatalysts is significantly beneficial to react with the deposited carbon in-situ during the DRM reaction. This review first discusses the state-of-the-art nanocatalysts being applied in the DRM reaction. Then, the effects of the type and physicochemical properties of the nanocatalysts on their catalytic performance in the DRM are outlined, followed by the elaboration of carbon gasification route/mechanism in the DRM reaction. Finally, a critical discussion on the kinetics of carbon gasification is detailed. This review can serve as a current knowledge base to encourage the continuous development of in-depth study of this promising catalytic field, especially the development of active yet stable nanocatalysts, which can contribute to valorization of carbon emissions