36 research outputs found

    Enzymatic biodiesel production from sludge palm oil (SPO) using locally produced Candida cylindracea lipase

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    Biodiesel is a non-toxic, renewable and environmental friendly fuel. This study involved the production of biodiesel from sludge palm oil (SPO), a low-cost waste oil via enzymatic catalysis. The enzyme catalyst was a Candida cylindracea lipase, locally-produced using palm oil mill effluent as the low cost based medium. The results in solvent system for biodiesel production showed that ethanol gave higher yield of biodiesel as compared to methanol. One-factor-at-a time (OFAT) method was applied to investigate several factors for enzymatic biodiesel production. The optimum levels of ethanol-to-SPO molar ratio, enzyme loading, reaction temperature, mixing speed and reaction time were 4:1, 10 U, 40°C, 250 rpm and 24 h, respectively with maximum yield of biodiesel of 62.3% (w/w SPO). The SPO had a promising potential for enzymatic biodiesel production using locally-produced lipase.Keywords: Biodiesel, sludge palm oil, lipase, free fatty acid, fatty acid alkyl esterAfrican Journal of Biotechnology Vol. 12(31), pp. 4966-497

    Roles of thiolate ligands in the synthesis, properties and catalytic application of gold nanoclusters

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    Ultrasmall (<2 nm) ligand-protected metal nanoclusters (NCs) have been an emerging class of functional materials with rich coordination chemistry, finding increasing acceptance in both basic and applied research owing to their atomic precision, well-defined molecular structure, and intriguing molecular-like properties. The presence of ligands on metal NCs is crucial not only for maintaining their atomic precision and well-defined structure, but also for their rich coordination chemistry with noble metals, influencing the synthesis, and physicochemical and catalytic properties of metal NCs. In this review, we discuss the important roles of ligands to metal NCs, taking water-soluble gold nanoclusters (Au NCs) as an exampl e. The review covers the fundamental understandings (and advances) on the roles of ligands to water-soluble Au NCs in the synthesis (e.g., influencing the size and formation rate, and revealing the growth mechanisms), physicochemical properties (e.g., geometrical structure, chirality, stability, solubility, and electronic, photoluminescence and biological properties) and catalytic applications (e.g., accessibility, activity, selectivity, and coordination of catalytic mechanism of quasi-homogeneous catalysts and immobilization of heterogeneous catalysts). The review also highlights some challenging issues on how ligands and ligand engineering could expand the scope of metal NCs in the synthesis, physicochemical properties, and catalytic application

    Statistical optimization of ethanol-based biodiesel production from sludge palm oil using locally produced candida cylindracea lipase

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    Face centered central composite design was used to optimize the enzyme loading, reaction temperature and mixing speed of sludge palm oil (SPO) transesterification reaction using locally produced Candida cylindracea lipase. The developed quadratic model was found to be significant at p < 0.05. The highest biodiesel yield of 57.5 % (w/w SPO) and 15.22 % free fatty acids (FFA) conversion to biodiesel with coefficient of determination R2 of 0.91 and 0.93, respectively were obtained at enzyme loading of 0.4 U/g SPO, 41 °C and 250 rpm mixing speed. Enzyme loading (U/g) gave little effect on the %FFA conversion to biodiesel and total biodiesel yield compared to temperature and mixing speed due to high FFA and water content, thus further studies are required for improvement. The study shows the low cost SPO and locally produced lipase have a promising potential in the utilization of waste for low cost biodiesel production

    Enhancing catalytic properties of ligand-protected gold-based 25-metal atom nanoclusters by silver doping

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    Herein, engineering metal composition of metal nanoclusters (NCs) by foreign metal doping was used as an approach to synthesize gold (Au)-based 25-metal NC catalysts, without compromising the presence of their ligands and unique structure of 25 metal atoms. The Au-based 25-metal atom NCs with silver doping which can also be called as bimetallic AuAg NCs (i.e., Au25-xAgx(SR)18 NCs with x = 4–12) were successfully synthesized by co-reduction method with various feeding ratios (RAu/Ag = 24/1, 22/3 and 18/7). The Ag dopants favorably replaced Au(0) atom on the vertex of the icosahedral core and enhanced the catalytic activity of bimetallic Au25-xAgx(SR)18 NCs due to combination of several factors. As compared to monometallic Au25(SR)18 NCs, Au25-xAgx(SR)18 NCs have (1) synergistic effects of Au and Ag atoms; (2) better ligands removal's and active sites exposure due to weaker Ag-SR bond than Au-SR bond based on DFT analysis; (3) weaker Ag-H than Au-H bond based on DFT analysis; and (4) better stability as smaller metal NCs during the catalytic reaction. The study reveals a wider opportunity to tailor the catalytic properties of atomically precise Au-based 25-metal atom NC by engineering its metal composition

    The importance of a standardized Islamic manufacturing (IMP) for food and pharmaceutical productions

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    As Muslims, the search for lawful (halal) and wholesome (tayyib) products such as food and medicines is not only a part of ibadah and to get pleasure of Allah SWT. In fact, it can also nourish the bodies and souls due to the permissibility and purity of the products. Currently, the awareness of some doubtful and questionable ingredients in the food and pharmaceutical products in the market has increased. Since the 23rd meeting of the Standing Committee for Economic and Commercial Cooperation (COMCEC) on November 2007, OIC has organized a conference and its sequential meeting on The OIC Halal Food Standard. Three main documents – OIC General Guidelines on Halal Food, Guidelines for Bodies Providing Halal Certification, and Guidelines for the Authorized Accreditation Body Accrediting Halal Certification Bodies – have been finalized. However, the concern is now wider and more complex in nature incorporating not only the traditional aspects but also the biopharmaceutical manufacturing processes and other relevant processes. Thus, there is an urgent need for a comprehensive guideline. The concept of Islamic Manufacturing Practice (IMP) has been introduced in Malaysia to fill this void but unfortunately, the contents of the IMP are still equivocal and limited. This paper discusses about some aspects of manufacturing processes in food and pharmaceutical industries that reflect the importance of a standardized IMP

    Golden carbon nanotube membrane for continuous flow catalysis

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    In this work, a high-performance catalytic membrane, composed of ultrasmall gold nanoclusters (AuNCs) and high aspect-ratio carbon nanotubes (CNTs), was designed for the continuous-flow catalytic reactions. In this hybrid catalytic membrane, the Au core of the NCs serves as high-performance catalyst, and the ligand of the NCs plays two key roles: (1) as a well-defined surfactant assembly to effectively dissolve CNTs in aqueous solution and (2) as an efficient protecting ligand for Au core to avoid agglomeration. Due to the above-mentioned features, a homogeneous 3D self-support catalytic membrane can be readily fabricated by vacuum filtration of the hybrid AuNCs/CNTs. The catalytic activity of the as-designed catalytic membrane was evaluated using 4-nitrophenol hydrogenation as a model catalytic reaction. The data suggest that the continuous flow catalytic reactor could achieve complete conversion of the substrate (i.e., 4-nitrophenol) within a single flow through the membrane with a hydraulic residence time (τ) of 3.0 s. The catalytic membrane also showed enhanced catalytic kinetics as compared to the conventional batch reactor due to the convectively enhanced mass transfer. In addition, three important parameters, including the Au loading amount, substrate concentration, and flow rate, were identified as key factors that could affect the performance of the catalytic membrane

    Heating or cooling: temperature effects on the synthesis of atomically precise gold nanoclusters

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    Developing an efficient, well-controlled synthesis strategy for gold nanoclusters (Au NCs) is crucial for delivering their expected applications in many fields; and such development requires fundamental understandings on the synthetic chemistry. The synthesis of Au NCs typically consists of a pair of reversible reactions: a fast reduction-growth reaction and a slow size-focusing reaction. Here we demonstrate that the above two reactions can be well-balanced while accelerated in a heated synthesis protocol, thus providing an efficient and scalable synthesis method to obtain thermodynamically favorable Au25(SR)18 NCs (SR denotes thiolate ligand) with high yield (>95% on gold atom basis) and fast kinetics. By investigating the Au NC formation behavior at different temperature, we identified the endothermic nature of the reductive formation of Au25(SR)18 NCs from Au(I)-thiolate complex precursors. More interestingly, if overheated, after the formation of Au25(SR)18, there exists an irreversible first-order reaction, which could transform Au25(SR)18 into Au NCs of mixed sizes. As a result, 40 °C is identified as the optimal temperature to synthesize Au25(SR)18 in aqueous solution, as the half-life of the transformation reaction (67.8 h) is much longer than the time needed to obtain high yield Au25(SR)18. The detailed understandings on the temperature effects of Au NC synthesis would facilitate the development of efficient synthesis strategies for atomically precise Au NCs with predesigned size, composition and structure

    Toward greener synthesis of gold nanomaterials: from biological to biomimetic synthesis

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    In the past two decades, the use of biomolecules, either from biological or biomimetic systems (or so-called biological or biomimetic synthesis), has emerged as a promising green approach to synthesize gold nanomaterials (Au NMs). Here, we describe recent progress on the biological and biomimetic syntheses of Au NMs. We focus our discussions on the selection principles of biomolecules, synthesis mechanisms involving biomolecules, recent evolution from biological to biomimetic synthesis, and the contributions of bioinspired synthesis to green production of Au NMs. We hope this review will provide a guideline for the green synthesis of Au NMs and other metal NMs, further paving their way toward practical applications in the field of biomedicine

    Evaluating the potential of chitin extracted from shrimp shell wastes as support material of gold nanoclusters (AuNCs) for catalysis

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    Thiolate-protected gold nanoclusters (AuNCs) have been intensively studied due to their appealing physicochemical properties that can be used in various applications, especially catalysis. However, thiolate-protected AuNCs in a free suspension form, tend to aggregate during catalytic reaction due to the high surface reactivity of its ultrasmall size, hence, reducing the rate of their catalytic reaction. Their recovery and reusability are also difficult. Therefore, several support materials have been studied to immobilize the thiolate-protected AuNCs for a better recovery, reusability and stability in solution and during a catalytic reaction. Herein, chitin extracted from shrimp shell waste was used as support material for the immobilization of the AuNCs protected by p-mercaptobenzoic acid ligands, using the deposition-precipitation method. The free chitin and chitin immobilized with thiolate-protected AuNCs (abbreviated as AuNCs/Chitin) were characterized using FTIR. The catalytic properties of the AuNCs/Chitin were then evaluated in the hydrogenation of 4-nitrophenol in solution as the model reaction. It was found that the chitin extracted from SSW has a good potential to be support materials of thiolate-protected AuNCs because of the shorter reaction time it took (12 minutes) as compared to the reaction without catalyst (60 minutes) and it can be recovered and reused twice

    Rational design of high-performance continuous-flow microreactors based on gold nanoclusters and graphene for catalysis

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    In this work, we rationally designed a high-performance microreactor system for continuous-flow catalysis. The membrane consists of ultrasmall gold nanoclusters (AuNCs) and two-dimensional graphene. The Au cores of the NCs act as catalysts, while their ligands have two functions: (1) protecting the Au cores to avoid agglomeration and (2) providing a well-defined surfactant assembly to disperse graphene in aqueous solution. Hydrogenation of 4-nitrophenol (4-NP) was employed as model reaction to evaluate catalytic activity. The catalytic membrane microreactor demonstrated excellent catalytic activity and stability, where complete 4-NP conversion was readily achieved via a single pass through the membrane. This desirable performance was maintained over 12 h of continuous operation, although a certain amount of organic buildup on the membrane was observed. The catalytic membrane microreactor outperforms conventional batch reactors due to its improved mass transport. 4-NP-spiked real water samples were also completely converted. This study provides new insights for the rational design of membrane reactors for industrial applications
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