Abu Bakar Salleh

Putra University, Malaysia, Putrajaya, Putrajaya, Malaysia

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Publications (236)400.99 Total impact

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    ABSTRACT: N-trans feruloyltyramine amide was successfully synthesized from 4-hydroxy-3-methoxycinnamic acid and tyramine hydrochloride in a one-step lipase catalysed reaction. The use of immobilized lipase, lipozyme TL IM as the catalyst in the reaction allowed simple isolation of the enzyme from the products and other components in the reaction mixture. N-feruloyltyramine amide was characterized using Fourier Transform Infrared (FTIR) Spectroscopy, Proton Nuclear Magnetic Resonance (1H NMR) and elemental analysis. Under optimized conditions 93.5% yield was obtained when the process was carried out for 48 h using a molar ratio of cinnamic acid:tyramine HCl, 6:1 at 40°C. In addition, a rapid simple and sensitive HPLC-UV method was developed for the determination of N-feruloyltyramine using an ®Rp-8 endcapped column. The optimum mobile phase used was acetonitrile:disodium hydrogen phosphate, 30:70(v/v.). N-feruloyltyramine amide was detected at a retention time of 12 min. The calibration curve was linear over the range of 5.27–12.30 × 10−4 M with correlation factor r = 0.9958. Consequently, the method was considered valid for quantitative analysis samples of N-trans-feruloyltyramine amide.
    Biocatalysis and Biotransformation 09/2012; 30(4). DOI:10.3109/10242422.2012.701623 · 1.09 Impact Factor
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    ABSTRACT: The substitution of the oxyanion Q114 with Met and Leu was carried out to investigate the role of Q114 in imparting enantioselectivity on T1 lipase. The mutation improved enantioselectivity in Q114M over the wild-type, while enantioselectivity in Q114L was reduced. The enantioselectivity of the thermophilic lipases, T1, Q114L and Q114M correlated better with log p as compared to the dielectric constant and dipole moment of the solvents. Enzyme activity was good in solvents with log p < 3.5, with the exception of hexane which deviated substantially. Isooctane was found to be the best solvent for the esterification of (R,S)-ibuprofen with oleyl alcohol for lipases Q114M and Q114L, to afford E values of 53.7 and 12.2, respectively. Selectivity of T1 was highest in tetradecane with E value 49.2. Solvents with low log p reduced overall lipase activity and dimethyl sulfoxide (DMSO) completely inhibited the lipases. Ester conversions, however, were still low. Molecular sieves employed as desiccant were found to adversely affect catalysis in the lipase variants, particularly in Q114M. The higher desiccant loading also increased viscosity in the reaction and further reduced the efficiency of the lipase-catalyzed esterifications.
    International Journal of Molecular Sciences 09/2012; 13(9):11666-80. DOI:10.3390/ijms130911666 · 2.34 Impact Factor
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    ABSTRACT: PpCHS is a member of the type III polyketide synthase family and catalyses the synthesis of the flavonoid precursor naringenin chalcone from p-coumaroyl-CoA. Recent research reports the production of pyrone derivatives using either hexanoyl-CoA or butyryl-CoA as starter molecule. The Cys-His-Asn catalytic triad found in other plant chalcone synthase predicted polypeptides is conserved in PpCHS. Site directed mutagenesis involving these amino acids residing in the active-site cavity revealed that the cavity volume of the active-site plays a significant role in the selection of starter molecules as well as product formation. Substitutions of Cys 170 with Arg and Ser amino acids decreased the ability of the PpCHS to utilize hexanoyl-CoA as a starter molecule, which directly effected the production of pyrone derivatives (products). These substitutions are believed to have a restricted number of elongations of the growing polypeptide chain due to the smaller cavity volume of the mutant's active site.
    International Journal of Molecular Sciences 08/2012; 13(8):9673-91. DOI:10.3390/ijms13089673 · 2.34 Impact Factor
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    ABSTRACT: Enzymatic production of fatty acid esters from the esterification of oleyl alcohol with various fatty acids was investigated by using two new tetraethylammonium amino acid ionic liquids-coated Candida rugosa lipase (ILs-CRL) as biocatalysts in hexane. Both enzyme derivatives were prepared by mixing Candida rugosa lipase with tetraethylammonium l-histidinate (IL1) and tetraethylammonium l-asparaginate (IL2). The ILs-CRL system containing the equivalent protein concentration as in CRL showed higher esterification activity especially on medium chain fatty acids (C 12 –C 16) as compared to non-coated CRL. Hydrophilicity of ILs may play an important role in hydrogen bonding with enzyme surface and consequently stabilize the ILs-CRL.
    Journal of Molecular Catalysis B Enzymatic 07/2012; 79:61-65. DOI:10.1016/j.molcatb.2012.03.003 · 2.75 Impact Factor
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    ABSTRACT: An electrochemical biosensor was developed based on formaldehyde dehydrogenase immobilized with Nafion membrane for determination of formaldehyde in fish. The enzyme was immobilized through the entrapment technique and measured based on the reduction of -nicotinamide adenine dinucleotide. The response time of the formaldehyde biosen-sor was <1 min, with an optimum pH of 8. The optimum enzyme loading and NAD + concentrations were found at 30 mg/mL and 0.5 mM, respectively. Using the formaldehyde biosensor, a linear response of formaldehyde showed a range of 0.1 to 10 ppm and a detection limit of 0.016 ppm. In application of Nash method, the samples were stored at 4 o C ± 1 for 10 days. With the two combined methods, a linear correlation coefficient with R 2 = 0.9982 (y = 0.956x -0.014) was found. The developed formaldehyde biosensor showed a good reproducibility, long storage stability (more than 6 months stored at 4 o C), and also effective monitoring of formaldehyde level in Indian mackerel (Rastrelliger kanagurta) fish.
    Current Analytical Chemistry 07/2012; 8(2.134). DOI:10.2174/157341112803216843 · 1.19 Impact Factor
  • Chemical Product and Process Modeling 07/2012; DOI:10.1515/1934-2659.1483
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    ABSTRACT: Purpose – The purpose of this paper is to describe a capacitive biosensor device consisting of an enzyme electrode and a simple detector which has been developed for histamine measurement. Design/methodology/approach – In this analysis, degradation of histamine through enzymatic reaction produces signal that is monitored using a simple detector equipped with “astable” multivibrator operation circuit (in capacitor-resistor circuit). Findings – Different frequency (f) readings have been obtained for glucose, alcohol and histamine in different concentration levels, showing the ability of this simple device system to measure their dielectric constant (k) as formulated by the equation f=(1.44d)/ [kA (R1+2R2)]. The analysis using smaller electrode gap (d) produces higher value of f, indicating that d, is directly proportional to f. For histamine, by using immobilized enzyme electrode, the results show that the change of dielectric properties during the 300-second reaction period could also be monitored. A linear relationship is obtained between concentration and frequency from 50 to 200?ppm. Practical implications – Based on this result, an enzyme electrode and “astable” operation circuits have the potential to be used in the development of a simple capacitive biosensor device. Originality/value – The paper is an outcome of experimental work carried out to observe capacitive sensing behavior using an immobilized enzyme, to measure biological samples, especially histamine.
    Sensor Review 06/2012; 32(3):245-250. DOI:10.1108/02602281211233241 · 0.62 Impact Factor
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    ABSTRACT: The activation of lipases has been postulated to proceed by interfacial activation, temperature switch activation, or aqueous activation. Recently, based on molecular dynamics (MD) simulation experiments, the T1 lipase activation mechanism was proposed to involve aqueous activation in addition to a double-flap mechanism. Because the open conformation structure is still unavailable, it is difficult to validate the proposed theory unambiguously to understand the behavior of the enzyme. In this study, we try to validate the previous reports and uncover the mystery behind the activation process using structural analysis and MD simulations. To investigate the effects of temperature and environmental conditions on the activation process, MD simulations in different solvent environments (water and water-octane interface) and temperatures (20, 50, 70, 80, and 100°C) were performed. Based on the structural analysis of the lipases in the same family of T1 lipase (I.5 lipase family), we proposed that the lid domain comprises α6 and α7 helices connected by a loop, thus forming a helix-loop-helix motif involved in interfacial activation. Throughout the MD simulations experiments, lid displacements were only observed in the water-octane interface, not in the aqueous environment with respect to the temperature effect, suggesting that the activation process is governed by interfacial activation coupled with temperature switch activation. Examining the activation process in detail revealed that the large structural rearrangement of the lid domain was caused by the interaction between the hydrophobic residues of the lid with octane, a nonpolar solvent, and this conformation was found to be thermodynamically favorable.
    Protein Science 06/2012; 21(8):1210-21. DOI:10.1002/pro.2108 · 2.86 Impact Factor
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    ABSTRACT: BACKGROUND: Pesticides are developed with carriers to improve their physicochemical properties and, accordingly, the bioefficacy of the applied formulation. For foliar-applied herbicide, generally less than 0.1% of the active ingredient reaching the target site could reduce pesticide performance. Recently, a carrier of nanoemulsion consisting of oil, surfactant and water, with a particle size of less than 200 nm, has been shown to enhance drug permeability for skin penetration in pharmaceutical delivery systems. In the present work, the aim was to formulate a water-soluble herbicide, glyphosate isopropylamine (IPA), using a green nanoemulsion system for a biological activity study against the weeds creeping foxglove, slender button weed and buffalo grass. RESULTS: The nanoemulsion formulations displayed a significantly lower spray deposition on creeping foxglove (2.9-3.5 ng cm(-2) ), slender button weed (2.6-2.9 ng cm(-2) ) and buffalo grass (1.8-2.4 ng cm(-2) ) than Roundup(®) (3.7-5.1 ng cm(-2) ). The visible injury rates of weeds treated with the nanoemulsion formulations were statistically equivalent to those relating to Roundup(®) at 14 days after treatment, with a control range of 86.67-96.67%. CONCLUSION: It was hypothesised that the significant difference in spray deposition with equal injury rates can be attributed to enhanced bioactivity of the nanoemulsion formulations. This initial discovery could be the platform for developing better penetration of agrochemical formulations in the future. Copyright © 2012 Society of Chemical Industry.
    Pest Management Science 05/2012; DOI:10.1002/ps.3371 · 2.74 Impact Factor
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    ABSTRACT: In silico and experimental investigations were conducted to explore the effects of substituting hydrophobic residues, Val, Met, Leu, Ile, Trp, and Phe into Gln 114 of T1 lipase. The in silico investigations accurately predicted the enzymatic characteristics of the mutants in the experimental studies and provided rationalization for some of the experimental observations. Substitution with Leu successfully improved the conformational stability and enzymatic characteristics of T1 lipase. However, replacement of Gln114 with Trp negatively affected T1 lipase and resulted in the largest disruption of protein stability, diminished lipase activity and inferior enzymatic characteristics. These results suggested that the substitution of a larger residue in a densely packed area of the protein core can have considerable effects on the structure and function of an enzyme. This is especially true when the residue is next to the catalytic serine as demonstrated with the Phe and Trp mutation.
    Applied biochemistry and biotechnology 05/2012; 167(3):612-20. DOI:10.1007/s12010-012-9728-2 · 1.74 Impact Factor
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    ABSTRACT: Yeasts are a convenient platform for many applications. They have been widely used as the expression hosts. There is a need to have a new yeast expression system to contribute the molecular cloning demands. Eight yeast isolates were screened from various environment sources and identified through ribosomal DNA (rDNA) Internal Transcribed Spacer (ITS). Full sequence of the rDNA ITS region for each isolate was BLASTed and phylogenetic study was constructed by using MEGA4. Among the isolates, isolate WB from 'ragi' (used to ferment carbohydrates) could be identified as a new species in order Saccharomycetales according to rDNA ITS region, morphology and biochemical tests. Isolate SO (from spoiled orange), RT (rotten tomato) and RG (different type of 'ragi') were identified as Pichia sp. Isolates R1 and R2, S4 and S5 (from the surrounding of a guava tree) were identified as Issatchenkia sp. and Hanseniaspora sp., respectively. Geneticin, 50 µg/mL, was determined to be the antibiotic marker for all isolates excepted for isolates RT and SO which used 500 µg/mL and 100 µg/mL Zeocin, respectively. Intra-extracellular proteins were screened for lipolytic activity at 30°C and 70°C. Thermostable lipase activity was detected in isolates RT and R1 with 0.6 U/mg and 0.1 U/mg, respectively. In conclusion, a new yeast-vector system for isolate WB can be developed by using phleomycin or geneticin as the drugs resistance marker. Moreover, strains RT and R1 can be investigated as a novel source of a thermostable lipase.
    Acta biochimica Polonica 05/2012; 59(2):225-9. · 1.39 Impact Factor
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    ABSTRACT: The present invention discloses biologically pure cultures of Geobacillussp. strain ARM and Aneurinibacillus thermoaerophilus strain AFNA isolated from soil contaminated with oil; whereby the Geobacillus spstrain ARM is deposited under the accession number DSM 21496 at DeutscheSammlung von Mikroorganismen und Zellkulturen (DSMZ) and NCIMB 41583 at The National Collection of Industrial, Marine and Food Bacteria (NCIMB), UK, and Aneurinibacillus thermoaerophilusstrain AFNA is deposited under the accession number DSM 21497 at DeutscheSammlung von Mikroorganismen und Zellkulturen (DSMZ) Germany and NCIMB 41584 at The National Collection of Industrial, Marine and Food Bacteria (NCIMB), UK. Moreover, the Geobacillus sp. strain ARM and Aneurinibacillus thermoaerophilus strain AFNA is capable to produce a novel thermostable enzyme isolated and characterized from Geobacillus sp. Strain ARM and Aneurinibacillus thermoaerophilus strain AFNA. In addition, the present invention provides the use of Geobacillus sp. strain ARM and Aneurinibacillus thermoaerophilus strain AFNA producing thermostable lipase, for industrial applications such as in food industry, oil processing, and production of surfactants, oil processing, detergents, pesticides, environmental management and leather industry. In particular the use of ARM lipase for industrial applications such as in food industry, oil processing, production of surfactants, oil processing, detergents, pesticides, environmental management and leather industry.
    Ref. No: EP2450458, Year: 05/2012
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    Asian Journal of Chemistry 05/2012; 24(10):4601-4605. · 0.36 Impact Factor
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    ABSTRACT: A three-electrode system amperometric biosensor that consisted of screen-printed carbon paste working electrode (SPE), a commercial platinum rod counter electrode vs Ag/AgCl reference electrode was developed for rapid determination of histamine in prawns. The biosensor was designed from entrapping diamine oxidase (DAO) enzyme in a poly(2-hydroxyethyl methacrylate) (photoHEMA) film prepared via a simple and one-step direct photocuring process on a carbon paste screen-printed electrode (SPE). The photoHEMA film exhibited water absorption of 34.14% after four hours exposure to water and no leaching of DAO was observed from the hydrogel film. The histamine biosensor showed response time of < 50 s with a linear response range from 0 to 60 ppm histamine (R2 of 0.9946). The sensitivity of the biosensor was of 5.56 nAppm-1, with a limit detection of 0.65 ppm histamine. The performance of the fabricated biosensor in the analysis of histamine in tiger prawn (Penaeus monodon) samples was comparable to high performance liquid chromatography (HPLC). The three-electrode system was then converted to an all-screen-printed histamine biosensor by printing onto a polyester substrate with carbon paste to form the working and counter electrodes and Ag/AgCl paste as the reference electrode. The performance of all-screen-printed histamine biosensor was evaluated using potassium hexacyanoferrate (III) as a mediator deposited electrochemically on the carbon-paste SPE. The presence of this mediator demonstrated improvement to the response of the allscreen- printed histamine biosensor.
    International journal of electrochemical science 04/2012; 7(2.808):4702 - 4715. · 1.96 Impact Factor
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    ABSTRACT: Enzyme immobilisation technology is an effective means to improve sugar ester production through the employment of biocatalysts. In the present study, immobilisation of Candida rugosa (CRL) lipase onto amino-activated mica is performed via covalent bonding (namely Amino-CRL) and the cross-linking of lipases into nano-reactors through physical adsorption (namely NER-CRL). Free and immobilised lipases were tested for their esterification activities. Specific activities for Amino-CRL and NER-CRL increased by 2.4 and 2.6-fold, respectively, upon immobilisation. Extending this work, immobilised lipases have novel capabilities in the synthesis of sugar esters. The optimised conditions for sugar fatty acid ester syntheses are 48 h at 2:1 of molar ratio of lactose sugar to capric acid at 55 °C. Furthermore, a high operational stability with half-lives of over 13 and 10 runs was achieved for NER-CRL and Amino-CRL, respectively, indicating the efficiency of the immobilisation process.
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    ABSTRACT: A mutant of the lipase from Geobacillus sp. strain T1 with a phenylalanine to leucine substitution at position 16 was overexpressed in Escherichia coli strain BL21(De3)pLysS. The crude enzyme was purified by two-step affinity chromatography with a final recovery and specific activity of 47.4 and 6,315.8 U/mg, respectively. The molecular weight of the purified F16L lipase was approximately 43 kDa by 12% SDS-PAGE analysis. The F16L lipase was demonstrated to be a thermophilic enzyme due its optimum temperature at 70 °C and showed stability over a temperature range of 40-60 °C. The enzyme exhibited an optimum pH 7 in phosphate buffer and was relatively stable at an alkaline pH 8-9. Metal ions such as Ca(2+), Mn(2+), Na(+), and K(+) enhanced the lipase activity, but Mg(2+), Zn(2+), and Fe(2+) inhibited the lipase. All surfactants tested, including Tween 20, 40, 60, 80, Triton X-100, and SDS, significantly inhibited the lipolytic action of the lipase. A high hydrolytic rate was observed on long-chain natural oils and triglycerides, with a notable preference for olive oil (C18:1; natural oil) and triolein (C18:1; triglyceride). The F16L lipase was deduced to be a metalloenzyme because it was strongly inhibited by 5 mM EDTA. Moderate inhibition was observed in the presence of PMSF at a similar concentration, indicating that serine residues are involved in its catalytic action. Further, the activity was not impaired by water-miscible solvents, including methanol, ethanol, and acetone.
    The Protein Journal 02/2012; 31(3):229-37. DOI:10.1007/s10930-012-9395-8 · 1.04 Impact Factor
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    ABSTRACT: Mutant D311E and K344R were constructed using site-directed mutagenesis to introduce an additional ion pair at the inter-loop and the intra-loop, respectively, to determine the effect of ion pairs on the stability of T1 lipase isolated from Geobacillus zalihae. A series of purification steps was applied, and the pure lipases of T1, D311E and K344R were obtained. The wild-type and mutant lipases were analyzed using circular dichroism. The T(m) for T1 lipase, D311E lipase and K344R lipase were approximately 68.52 °C, 70.59 °C and 68.54 °C, respectively. Mutation at D311 increases the stability of T1 lipase and exhibited higher T(m) as compared to the wild-type and K344R. Based on the above, D311E lipase was chosen for further study. D311E lipase was successfully crystallized using the sitting drop vapor diffusion method. The crystal was diffracted at 2.1 Å using an in-house X-ray beam and belonged to the monoclinic space group C2 with the unit cell parameters a = 117.32 Å, b = 81.16 Å and c = 100.14 Å. Structural analysis showed the existence of an additional ion pair around E311 in the structure of D311E. The additional ion pair in D311E may regulate the stability of this mutant lipase at high temperatures as predicted in silico and spectroscopically.
    International Journal of Molecular Sciences 01/2012; 13(1):943-60. DOI:10.3390/ijms13010943 · 2.34 Impact Factor
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    ABSTRACT: A fast and improved lipase-catalyzed synthesis of galactose oleate ester was performed in 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF 4 ]) ionic liquid with the addition of dimethylsulfoxide (DMSO) as a solubilizing agent and co-solvent; and Lipozyme RM IM (lipase from Rhizomucor miehei immobilized on macroporous anion exchange resin) as the biocatalyst. Different reaction parameters (type of solvent, type of enzyme, amount of enzyme, reaction time, temperature, stirring rate and sub-strate molar ratio) were studied. A high conversion (87%) was obtained after only 2 h at optimal synthesis conditions (1:20 DMSO:[Bmim][BF 4 ] ratio with 2% (w/w) Lipozyme RM IM, temperature 60 • C, stirring rate of 300 rpm and a molar ratio of galactose to oleic acid of 1:3).
    Journal of Molecular Catalysis B Enzymatic 01/2012; 76:37-43. DOI:10.1016/j.molcatb.2011.12.004 · 2.75 Impact Factor
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    ABSTRACT: A thermophilic Bacillus stearothermophilus F1 produces an extremely thermostable serine protease. The F1 protease sequence was used to predict its three-dimensional (3D) structure to provide better insights into the relationship between the protein structure and biological function and to identify opportunities for protein engineering. The final model was evaluated to ensure its accuracy using three independent methods: Procheck, Verify3D, and Errat. The predicted 3D structure of F1 protease was compared with the crystal structure of serine proteases from mesophilic bacteria and archaea, and led to the identification of features that were related to protein stabilization. Higher thermostability correlated with an increased number of residues that were involved in ion pairs or networks of ion pairs. Therefore, the mutants W200R and D58S were designed using site-directed mutagenesis to investigate F1 protease stability. The effects of addition and disruption of ion pair networks on the activity and various stabilities of mutant F1 proteases were compared with those of the wild-type F1 protease.
    Journal of Microbiology and Biotechnology 01/2012; 22(1):34-45. · 1.32 Impact Factor
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    ABSTRACT: Palm oil esters (POEs), which are newly synthetic liquid wax esters with HLB value of 9.34, were proposed as a lipophilic phase for formation of nanoemulsion. Phase diagrams show domination of two-phase regions at all emulsification temperatures ranging from 30 to 80°C. Spontaneous and temperature-induced emulsification, high-shear and high pressure homogenization were utilized to form nanoemulsion. However, only high pressure homogenization successfully produced droplets sizes in the nano range. Thus, it was used to optimize the stability properties of POEs nanoemulsion. The manipulation of processing temperatures during the formation of emulsions could be used in lowering the droplets size of the emulsion.
    Journal of Dispersion Science and Technology 01/2012; 33(1-3). DOI:10.1080/01932691.2011.562440 · 0.71 Impact Factor

Publication Stats

2k Citations
400.99 Total Impact Points

Institutions

  • 1999–2015
    • Putra University, Malaysia
      • • Faculty of Biotechnology and Biomolecular Sciences
      • • Department of Biochemistry
      • • Faculty of Environmental Studies
      Putrajaya, Putrajaya, Malaysia
  • 2009–2012
    • Malaysia Genome Institute
      Kuala Lumpor, Kuala Lumpur, Malaysia
  • 2010
    • Institute of Microbial Technology
      Chandigarh, Chandigarh, India
  • 2003
    • National University of Malaysia
      • Department of Electrical, Electronic and Systems Engineering
      Putrajaya, Putrajaya, Malaysia