Displaying publications 21 - 40 of 75 in total

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  1. Insights into the stereospecificity of the d-specific dehalogenase from Rhizobium sp. RC1 toward d- and l-2-chloropropionate
    Sudi IY, Hamid AA, Shamsir MS, Jamaluddin H, Wahab RA, Huyop F
    Biotechnology, biotechnological equipment, 2014 Jul 04;28(4):608-615.
    PMID: 26740767
    Halogenated compounds are recalcitrant environmental pollutants prevalent in agricultural fields, waste waters and industrial by-products, but they can be degraded by dehalogenase-containing microbes. Notably, 2-haloalkanoic acid dehalogenases are employed to resolve optically active chloropropionates, as exemplified by the d-specific dehalogenase from Rhizobium sp. RCI (DehD), which acts on d-2-chloropropionate but not on its l-enantiomer. The catalytic residues of this dehalogenase responsible for its affinity toward d-2-chloropropionate have not been experimentally determined, although its three-dimensional crystal structure has been solved. For this study, we performed in silico docking and molecular dynamic simulations of complexes formed by this dehalogenase and d- or l-2-chloropropionate. Arg134 of the enzyme plays the key role in the stereospecific binding and Arg16 is in a position that would allow it to activate a water molecule for hydrolytic attack on the d-2-chloropropionate chiral carbon for release of the halide ion to yield l-2-hydroxypropionate. We propose that within the DehD active site, the NH group of Arg134 can form a hydrogen bond with the carboxylate of d-2-chloropropionate with a strength of ∼4 kcal/mol that may act as an acid-base catalyst, whereas, when l-2-chloropropionate is present, this bond cannot be formed. The significance of the present work is vital for rational design of this dehalogenase in order to confirm the involvement of Arg16 and Arg134 residues implicated in hydrolysis and binding of d-2-chloropropionate in the active site of d-specific dehalogenase from Rhizobium sp. RC1.
  2. Fulltext Combination of oxyanion Gln114 mutation and medium engineering to influence the enantioselectivity of thermophilic lipase from Geobacillus zalihae
    Wahab RA, Basri M, Rahman MB, Rahman RN, Salleh AB, Leow TC
    Int J Mol Sci, 2012;13(9):11666-80.
    PMID: 23109876 DOI: 10.3390/ijms130911666
    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.
  3. Manipulation of the conformation and enzymatic properties of T1 lipase by site-directed mutagenesis of the protein core
    Wahab RA, Basri M, Rahman RN, Salleh AB, Rahman MB, Chor LT
    Appl Biochem Biotechnol, 2012 Jun;167(3):612-20.
    PMID: 22581079 DOI: 10.1007/s12010-012-9728-2
    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.
  4. An overview of technologies for immobilization of enzymes and surface analysis techniques for immobilized enzymes
    Mohamad NR, Marzuki NH, Buang NA, Huyop F, Wahab RA
    Biotechnology, biotechnological equipment, 2015 Mar 04;29(2):205-220.
    PMID: 26019635
    The current demands of sustainable green methodologies have increased the use of enzymatic technology in industrial processes. Employment of enzyme as biocatalysts offers the benefits of mild reaction conditions, biodegradability and catalytic efficiency. The harsh conditions of industrial processes, however, increase propensity of enzyme destabilization, shortening their industrial lifespan. Consequently, the technology of enzyme immobilization provides an effective means to circumvent these concerns by enhancing enzyme catalytic properties and also simplify downstream processing and improve operational stability. There are several techniques used to immobilize the enzymes onto supports which range from reversible physical adsorption and ionic linkages, to the irreversible stable covalent bonds. Such techniques produce immobilized enzymes of varying stability due to changes in the surface microenvironment and degree of multipoint attachment. Hence, it is mandatory to obtain information about the structure of the enzyme protein following interaction with the support surface as well as interactions of the enzymes with other proteins. Characterization technologies at the nanoscale level to study enzymes immobilized on surfaces are crucial to obtain valuable qualitative and quantitative information, including morphological visualization of the immobilized enzymes. These technologies are pertinent to assess efficacy of an immobilization technique and development of future enzyme immobilization strategies.
  5. Interactions of non-natural halogenated substrates with D-specific dehalogenase (DehD) mutants using in silico studies
    Sudi IY, Shamsir MS, Jamaluddin H, Wahab RA, Huyop F
    Biotechnology, biotechnological equipment, 2014 Sep 03;28(5):949-957.
    PMID: 26019583
    The D-2-haloacid dehalogenase of D-specific dehalogenase (DehD) from Rhizobium sp. RC1 catalyses the hydrolytic dehalogenation of D-haloalkanoic acids, inverting the substrate-product configuration and thereby forming the corresponding L-hydroxyalkanoic acids. Our investigations were focused on DehD mutants: R134A and Y135A. We examined the possible interactions between these mutants with haloalkanoic acids and characterized the key catalytic residues in the wild-type dehalogenase, to design dehalogenase enzyme(s) with improved potential for dehalogenation of a wider range of substrates. Three natural substrates of wild-type DehD, specifically, monochloroacetate, monobromoacetate and D,L-2,3-dichloropropionate, and eight other non-natural haloalkanoic acids substrates of DehD, namely, L-2-chloropropionate; L-2-bromopropionate; 2,2-dichloropropionate; dichloroacetate; dibromoacetate; trichloroacetate; tribromoacetate; and 3-chloropropionate, were docked into the active site of the DehD mutants R134A and Y135A, which produced altered catalytic functions. The mutants interacted strongly with substrates that wild-type DehD does not interact with or degrade. The interaction was particularly enhanced with 3-chloropropionate, in addition to monobromoacetate, monochloroacetate and D,L-2,3-dichloropropionate. In summary, DehD variants R134A and Y135A demonstrated increased propensity for binding haloalkanoic acid and were non-stereospecific towards halogenated substrates. The improved characteristics in these mutants suggest that their functionality could be further exploited and harnessed in bioremediations and biotechnological applications.
  6. Candida rugosa Lipase Immobilized onto Acid-Functionalized Multi-walled Carbon Nanotubes for Sustainable Production of Methyl Oleate
    Che Marzuki NH, Mahat NA, Huyop F, Buang NA, Wahab RA
    Appl Biochem Biotechnol, 2015 Oct;177(4):967-84.
    PMID: 26267406 DOI: 10.1007/s12010-015-1791-z
    The chemical production of methyl oleate using chemically synthesized fatty acid alcohols and other toxic chemicals may lead to significant environmental hazards to mankind. Being a highly valuable fatty acid replacement raw material in oleochemical industry, the mass production of methyl oleate via environmentally favorable processes is of concern. In this context, an alternative technique utilizing Candida rugosa lipase (CRL) physically adsorbed on multi-walled carbon nanotubes (MWCNTs) has been suggested. In this study, the acid-functionalized MWCNTs prepared using a mixture of HNO3 and H2SO4 (1:3 v/v) was used as support for immobilizing CRL onto MWCNTs (CRL-MWCNTs) as biocatalysts. Enzymatic esterification was performed and the efficiency of CRL-MWCNTs was evaluated against the free CRL under varying conditions, viz. temperature, molar ratio of acid/alcohol, solvent log P, and enzyme loading. The CRL-MWCNTs resulted in 30-110 % improvement in the production of methyl oleate over the free CRL. The CRL-MWCNTs attained its highest yield (84.17 %) at 50 °C, molar ratio of acid/alcohol of 1:3, 3 mg/mL of enzyme loading, and iso-octane (log P 4.5) as solvent. Consequently, physical adsorption of CRL onto acid-functionalized MWCNTs has improved the activity and stability of CRL and hence provides an environmentally friendly means for the production of methyl oleate.
  7. Fulltext An S188V mutation alters substrate specificity of non-stereospecific α-haloalkanoic acid dehalogenase E (DehE)
    Hamid AA, Hamid TH, Wahab RA, Omar MS, Huyop F
    PLoS One, 2015;10(3):e0121687.
    PMID: 25816329 DOI: 10.1371/journal.pone.0121687
    The non-stereospecific α-haloalkanoic acid dehalogenase E (DehE) degrades many halogenated compounds but is ineffective against β-halogenated compounds such as 3-chloropropionic acid (3CP). Using molecular dynamics (MD) simulations and site-directed mutagenesis we show here that introducing the mutation S188V into DehE improves substrate specificity towards 3CP. MD simulations showed that residues W34, F37, and S188 of DehE were crucial for substrate binding. DehE showed strong binding ability for D-2-chloropropionic acid (D-2CP) and L-2-chloropropionic acid (L-2CP) but less affinity for 3CP. This reduced affinity was attributed to weak hydrogen bonding between 3CP and residue S188, as the carboxylate of 3CP forms rapidly interconverting hydrogen bonds with the backbone amide and side chain hydroxyl group of S188. By replacing S188 with a valine residue, we reduced the inter-molecular distance and stabilised bonding of the carboxylate of 3CP to hydrogens of the substrate-binding residues. Therefore, the S188V can act on 3CP, although its affinity is less strong than for D-2CP and L-2CP as assessed by Km. This successful alteration of DehE substrate specificity may promote the application of protein engineering strategies to other dehalogenases, thereby generating valuable tools for future bioremediation technologies.
  8. Fulltext Progress of Interfacial Polymerization Techniques for Polyamide Thin Film (Nano)Composite Membrane Fabrication: A Comprehensive Review
    Seah MQ, Lau WJ, Goh PS, Tseng HH, Wahab RA, Ismail AF
    Polymers (Basel), 2020 Nov 27;12(12).
    PMID: 33261079 DOI: 10.3390/polym12122817
    In this paper, we review various novel/modified interfacial polymerization (IP) techniques for the fabrication of polyamide (PA) thin film composite (TFC)/thin film nanocomposite (TFN) membranes in both pressure-driven and osmotically driven separation processes. Although conventional IP technique is the dominant technology for the fabrication of commercial nanofiltration (NF) and reverse osmosis (RO) membranes, it is plagued with issues of low membrane permeability, relatively thick PA layer and susceptibility to fouling, which limit the performance. Over the past decade, we have seen a significant growth in scientific publications related to the novel/modified IP techniques used in fabricating advanced PA-TFC/TFN membranes for various water applications. Novel/modified IP lab-scale studies have consistently, so far, yielded promising results compared to membranes made by conventional IP technique, in terms of better filtration efficiency (increased permeability without compensating solute rejection), improved chemical properties (crosslinking degree), reduced surface roughness and the perfect embedment of nanomaterials within selective layers. Furthermore, several new IP techniques can precisely control the thickness of the PA layer at sub-10 nm and significantly reduce the usage of chemicals. Despite the substantial improvements, these novel IP approaches have downsides that hinder their extensive implementation both at the lab-scale and in manufacturing environments. Herein, this review offers valuable insights into the development of effective IP techniques in the fabrication of TFC/TFN membrane for enhanced water separation.
  9. Haloadaptation: insights from comparative modeling studies between halotolerant and non-halotolerant dehalogenases
    Edbeib MF, Aksoy HM, Kaya Y, Wahab RA, Huyop F
    J Biomol Struct Dyn, 2020 Aug;38(12):3452-3461.
    PMID: 31422756 DOI: 10.1080/07391102.2019.1657498
    Halophiles are extremophilic microorganisms that grow optimally at high salt concentrations by producing a myriad of equally halotolerant enzymes. Structural haloadaptation of these enzymes adept to thriving under high-salt environments, though are not fully understood. Herein, the study attempts an in silico investigation to identify and comprehend the evolutionary structural adaptation of a halotolerant dehalogenase, DehHX (GenBank accession number: KR297065) of the halotolerant Pseudomonas halophila, over its non-halotolerant counterpart, DehMX1 (GenBank accession number KY129692) produced by Pseudomonas aeruginosa. GC content of the halotolerant DehHX DNA sequence was distinctively higher (58.9%) than the non-halotolerant dehalogenases (55% average GC). Its acidic residues, Asp and Glu were 8.27% and 12.06%, respectively, compared to an average 5.5% Asp and 7% Glu, in the latter; but lower contents of basic and hydrophobic residues in the DehHX. The secondary structure of DehHX interestingly revealed a lower incidence of α-helix forming regions (29%) and a higher percentage of coils (57%), compared to 49% and 29% in the non-halotolerant homologues, respectively. Simulation models showed the DehHX is stable under a highly saline environment (25% w/v) by adopting a highly negative-charged surface with a concomitant weakly interacting hydrophobic core. The study thus, established that a halotolerant dehalogenase undergoes notable evolutionary structural changes related to GC content over its non-halotolerant counterpart, in order to adapt and thrive under highly saline environments.Communicated by Ramaswamy H. Sarma.
  10. In silico mutation on a mutant lipase from Acinetobacter haemolyticus towards enhancing alkaline stability
    Anuar NFSK, Wahab RA, Huyop F, Halim KBA, Hamid AAA
    J Biomol Struct Dyn, 2020 Sep;38(15):4493-4507.
    PMID: 31630644 DOI: 10.1080/07391102.2019.1683074
    Alkaline-stable lipases are highly valuable biocatalysts that catalyze reactions under highly basic conditions. Herein, computational predictions of lipase from Acinetobacter haemolyticus and its mutant, Mut-LipKV1 was performed to identify functionally relevant mutations that enhance pH performance under increasing basicity. Mut-LipKV1 was constructed by in silico site directed mutagenesis of several outer loop acidic residues, aspartic acid (Asp) into basic ones, lysine (Lys) at positions 51, 122 and 247, followed by simulation under extreme pH conditions (pH 8.0-pH 12.0). The energy minimized Mut-LipKV1 model exhibited good quality as shown by PROCHECK, ERRAT and Verify3D data that corresponded to 79.2, 88.82 and 89.42% in comparison to 75.2, 86.15, and 95.19% in the wild-type. Electrostatic surface potentials and charge distributions of the Mut-LipKV1 model was more stable and better adapted to conditions of elevated pHs (pH 8.0 - 10.0). Mut-LipKV1 exhibited a mixture of neutral and positive surface charge distribution compared to the predominantly negative charge in the wild-type lipase at pH 8.0. Data of molecular dynamics simulations also supported the increased alkaline-stability of Mut-LipKV1, wherein the lipase was more stable at a higher pH 9.0 (RMSD = ∼0.3 nm, RMSF = ∼0.05-0.2 nm), over the optimal pH 8.0 of the wild-type lipase (RMSD = 0.3 nm, RMSF = 0.05-0.20 nm). Thus, the adaptive strategy of replacing surface aspartic acid to lysine in lipase was successful in yielding a more alkaline-stable Mut-LipKV1 under elevated basic conditions.Communicated by Ramaswamy H. Sarma.
  11. Structure and properties of lipase activated by cellulose-silica polyethersulfone membrane for production of pentyl valerate
    Elias N, Wahab RA, Chandren S, Jamalis J, Mahat NA, Jye LW
    Carbohydr Polym, 2020 Oct 01;245:116549.
    PMID: 32718641 DOI: 10.1016/j.carbpol.2020.116549
    Herein, this study extracted nanocrystalline cellulose (NC) and silica (SiO2) from raw oil palm leaves (OPL), and employed as nanofillers in polyethersulfone (PES) to produce NC-SiO2-PES as support to immobilize Candida rugosa lipase (CRL) (NC-SiO2-PES/CRL). XRD, TGA-DTG and FTIR-ATR data affirmed that NC and SiO2 were isolated from OPL with corresponding crystallinity indices of 68 % and 70 %. A 0.02 cm membrane size with 5% (w/v) of NC-SiO2 without PVP K30 was optimal for membrane fabrication. CRL immobilized on the Glut-AP-NC-SiO2-PES membrane gave a higher conversion of pentyl valerate (PeVa) (91.3 %, p < 0.05) compared to Glut-NC-SiO2-PES (73.9 %) (p < 0.05). Characterization of the NC-SiO2-PES/CRL biocatalyst verified the presence of CRL. Hence, raw OPL is a proven good source of NC and SiO2, as reinforcement nanofillers in PES. The overall findings envisage the promising use of NC-SiO2-PES/CRL to catalyze an expedient and high yield of PeVa, alongside the suitability of NC-SiO2-PES for activating other enzymes.
  12. Potassium Alum [KAl(SO4)2∙12H2O] solid catalyst for effective and selective methoxylation production of alpha-pinene ether products
    Wijayati N, Lestari LR, Wulandari LA, Mahatmanti FW, Rakainsa SK, Cahyono E, et al.
    Heliyon, 2021 Jan;7(1):e06058.
    PMID: 33553744 DOI: 10.1016/j.heliyon.2021.e06058
    Methoxylation is a relevant technological process applied in the production of high-value α-pinene derivatives. This report investigates the use of potassium alum [KAl(SO4)2 · 12H2O] as a catalyst in the methoxylation of α-pinene. In this study, the methoxylation reaction was optimized for the highest conversion of α-pinene and selectivity, assessed for the factors, catalyst loading (0.5; 1.0; and 1.5 g), volume ratio of α-pinene: methanol (1:4, 1:7, 1:10), reaction temperature (50, 55, 60 and 65 °C), and reaction time (72, 144, 216, 288, 360 min). The highest selectivity of KAl(SO4)2∙12H2O in the methoxylation of α-pinene was achieved under an optimal condition of 1 g of catalyst loading, volume ratio of 1:10, as well as the reaction temperature and incubation time of 65 °C and 6 h, respectively. GC-MS results revealed the yields of the methoxylated products from the 98.2% conversion of α-pinene, to be 59.6%, 8.9%, and 7.1% for α-terpinyl methyl ether (TME), fenchyl methyl ether (FME), bornyl methyl ether (BME), respectively. It was apparent that a lower KAl(SO4)2∙12H2O loading (0.5-1.5 g) was more economical for the methoxylation reaction. The findings seen here indicated the suitability of the KAl(SO4)2 · 12H2O to catalyze the methoxylation of α-pinene to produce an commercially important ethers.
  13. Effect of operative variables and kinetic study of butyl butyrate synthesis by Candida rugosa lipase activated by chitosan-reinforced nanocellulose derived from raw oil palm leaves
    Elias N, Wahab RA, Chandren S, Abdul Razak FI, Jamalis J
    Enzyme Microb Technol, 2019 Nov;130:109367.
    PMID: 31421729 DOI: 10.1016/j.enzmictec.2019.109367
    Currently, the chemically-assisted esterification to manufacture butyl butyrate employs corrosive homogeneous acid catalyst and liberates enormous quantities of hazardous by-products which complicate downstream treatment processes. This study aimed to identify the optimized esterification conditions, and the kinetic aspects of the enzyme-assisted synthesis of butyl butyrate using immobilized Candida rugosa lipase activated by chitosan-reinforced nanocellulose derived from raw oil palm leaves (CRL/CS-NC). The best process variables that gave the maximum conversion degree of butyl butyrate by CRL/CS-NC (90.2%) in just 3 h, as compared to free CRL (62.9%) are as follows: 50 °C, 1:2 M ratio of acid/alcohol, stirring rate of 200 rpm and a 3 mg/mL enzyme load. The enzymatic esterification followed the ping pong bi-bi mechanism with substrate inhibition, revealing a ˜1.1-fold higher Ki for CRL/CS-NC (55.55 mM) over free CRL (50.68 mM). This indicated that CRL/CS-NC was less inhibited by the substrates. Butanol was preferred over butyric acid as reflected by the higher apparent Michaelis-Menten constant of CRL/CS-NC for butanol (137 mM) than butyric acid (142.7 mM). Thus, the kinetics data conclusively showed that CRL/CS-NC (Vmax 0.48 mM min-1, Keff 0.07 min-1 mM-1) was catalytically more efficient than free CRL (Vmax 0.35 mM min-1, Keff 0.06 min-1 mM-1).
  14. Enzymatic esterification of eugenol and benzoic acid by a novel chitosan-chitin nanowhiskers supported Rhizomucor miehei lipase: Process optimization and kinetic assessments
    Manan FMA, Attan N, Zakaria Z, Keyon ASA, Wahab RA
    Enzyme Microb Technol, 2018 Jan;108:42-52.
    PMID: 29108626 DOI: 10.1016/j.enzmictec.2017.09.004
    A biotechnological route via enzymatic esterification was proposed as an alternative way to synthesize the problematic anti-oxidant eugenyl benzoate. The new method overcomes the well-known drawbacks of the chemical route in favor of a more sustainable reaction process. The present work reports a Box-Behnken design (BBD) optimization process to synthesize eugenyl benzoate by esterification of eugenol and benzoic acid catalyzed by the chitosan-chitin nanowhiskers supported Rhizomucor miehei lipase (RML-CS/CNWs). Effects of four reaction parameters: reaction time, temperature, substrate molar ratio of eugenol: benzoic acid and enzyme loading were assessed. Under optimum conditions, a maximum conversion yield as high as 66% at 50°C in 5h using 3mg/mL of RML-CS/CNWs, and a substrate molar ratio (eugenol: benzoic acid) of 3:1. Kinetic assessments revealed the RML-CS/CNWs catalyzed the reaction via a ping-pong bi-bi mechanism with eugenol inhibition, characterized by a Vmax of 3.83mMmin-1. The Michaelis-Menten constants for benzoic acid (Km,A) and eugenol (Km,B) were 34.04 and 138.28mM, respectively. The inhibition constant for eugenol (Ki,B) was 438.6mM while the turnover number (kcat) for the RML-CS/CNWs-catalyzed esterification reaction was 40.39min-1. RML-CS/CNWs were reusable up to 8 esterification cycles and showed higher thermal stability than free RML.
  15. Fulltext The promise of zebrafish as a model of metabolic syndrome
    Benchoula K, Khatib A, Jaffar A, Ahmed QU, Sulaiman WMAW, Wahab RA, et al.
    Exp Anim, 2019 Nov 06;68(4):407-416.
    PMID: 31118344 DOI: 10.1538/expanim.18-0168
    Metabolic syndrome is a cluster including hyperglycaemia, obesity, hypertension, and hypertriglyceridaemia as a result of biochemical and physiological alterations and can increase the risk of cardiovascular disease and diabetes. Fundamental research on this disease requires validated animal models. One potential animal model that is rapidly gaining in popularity is zebrafish (Danio rerio). The use of zebrafish as an animal model conveys several advantages, including high human genetic homology, transparent embryos and larvae that allow easier visualization. This review discusses how zebrafish models contribute to the development of metabolic syndrome studies. Different diseases in the cluster of metabolic syndrome, such as hyperglycaemia, obesity, diabetes, and hypertriglyceridaemia, have been successfully studied using zebrafish; and the model is promising for hypertension and cardiovascular metabolic-related diseases due to its genetic similarity to mammals. Genetic mutation, chemical induction, and dietary alteration are among the tools used to improve zebrafish models. This field is expanding, and thus, more effective and efficient techniques are currently developed to fulfil the increasing demand for thorough investigations.
  16. Fulltext Occurrence of Intestinal Parasitic Contamination in Select Consumed Local Raw Vegetables and Fruits in Kuantan, Pahang
    Yusof AM, Mohammad M, Abdullahi MA, Mohamed Z, Zakaria R, Wahab RA
    Trop Life Sci Res, 2017 Jan;28(1):23-32.
    PMID: 28228914 MyJurnal DOI: 10.21315/tlsr2017.28.1.2
    Intestinal parasitic infections are one of the most common causes of human diseases that result in serious health and economic issues in many developing and developed countries. Raw vegetables and fruits play an important role in transmitting parasites to humans. Hence, the aim of this study was to investigate the parasitological contamination of select commonly consumed local leafy vegetables and fruits in Kuantan, Malaysia. One kilogram of locally consumed raw vegetables and fruits were collected randomly from the Kuantan wet market (Pasar Tani) during the monsoon season (November 2014-January 2015) and the dry season (February 2015-April 2015). A standard wet mount procedure and modified Ziehl-Neelsen staining were used for the detection of parasites. In the present study, the examination of vegetables revealed five different parasite species. The vegetable samples collected from Kuantan's wet market were positive for both helminthes and protozoa. However, the fruits samples were negative for parasitic contamination. Pegaga was the most contaminated leafy vegetable in this study, and Strongyloides was the parasite found most frequently. Furthermore, there was a high diversity in the type of parasites observed during the dry season compared to the monsoon season. Therefore, further action should be taken to reduce the occurrence of parasitic contamination in vegetables by implementing the principles of good agricultural practice and improving water treatment efficacy.
  17. Molecular docking and molecular dynamics simulations studies on β-glucosidase and xylanase Trichoderma asperellum to predict degradation order of cellulosic components in oil palm leaves for nanocellulose preparation
    Bahaman AH, Wahab RA, Abdul Hamid AA, Abd Halim KB, Kaya Y
    J Biomol Struct Dyn, 2021 Apr;39(7):2628-2641.
    PMID: 32248752 DOI: 10.1080/07391102.2020.1751713
    Literature has shown that oil palm leaves (OPL) can be transformed into nanocellulose (NC) by fungal lignocellulosic enzymes, particularly those produced by the Trichoderma species. However, mechanism of β-glucosidase and xylanase selectivity to degrade lignin, hemicellulose and cellulose in OPL for NC production remains relatively vague. The study aimed to comprehend this aspect by an in silico approach of molecular docking, molecular dynamics (MD) simulation and Molecular-mechanics Poisson-Boltzmann surface area (MM-PBSA) analysis, to compare interactions between the β-glucosidase- and xylanase from Trichoderma asperellum UC1 in complex with each substrate. Molecular docking of the enzyme-substrate complex showed residues Glu165-Asp226-Glu423 and Arg155-Glu210-Ser160 being the likely catalytic residues of β-glucosidase and xylanase, respectively. The binding affinity of β-glucosidase for the substrates are as follows: cellulose (-8.1 kcal mol-1) > lignin (-7.9 kcal mol-1) > hemicellulose (-7.8 kcal mol-1), whereas, xylanase showed a corresponding preference for; hemicellulose (-6.7 kcal mol-1) > cellulose (-5.8 kcal mol-1) > lignin (-5.7 kcal mol-1). Selectivity of both enzymes was reiterated by MD simulations where interactions between β-glucosidase-cellulose and xylanase-hemicellulose were the strongest. Notably low free-binding energy (ΔGbind) of β-glucosidase and xylanase in complex with cellulose (-207.23 +/- 47.13 kJ/mol) and hemicellulose (-131.48 +/- 24.57 kJ/mol) were observed, respectively. The findings thus successfully identified the cellulose component selectivity of the polymer-acting β-glucosidase and xylanase of T. asperellum UC1.Communicated by Ramaswamy H. Sarma.
  18. Statistical optimization and operational stability of Rhizomucor miehei lipase supported on magnetic chitosan/chitin nanoparticles for synthesis of pentyl valerate
    Rahman INA, Attan N, Mahat NA, Jamalis J, Abdul Keyon AS, Kurniawan C, et al.
    Int J Biol Macromol, 2018 Aug;115:680-695.
    PMID: 29698760 DOI: 10.1016/j.ijbiomac.2018.04.111
    The chemical-catalyzed transesterification process to produce biofuels i.e. pentyl valerate (PeVa) is environmentally unfriendly, energy-intensive with tedious downstream treatment. The present work reports the use of Rhizomucor miehei lipase (RML) crosslinked onto magnetic chitosan/chitin nanoparticles (RML-CS/CH/MNPs). The approach used to immobilize RML onto the CS/CH/MNPs yielded RML-CS/CH/MNPs with an immobilized protein loading and specific activity of 7.6 mg/g and 5.0 U·g-1, respectively. This was confirmed by assessing data of field emission scanning electron microscopy, X-ray diffraction, thermal gravimetric analysis and Fourier transform infrared spectroscopy. A three-level-four-factor Box-Behnken design (incubation time, temperature, substrate molar ratio, and enzyme loading) was used to optimize the RML-CS/CH/MNP-catalyzed esterification synthesis of PeVa. Under optimum condition, the maximum yield of PeVa (97.8%) can be achieved in 5 h at 50 °C using molar ratio valeric acid:pentanol (1:2) and an enzyme load of 2 mg/mL. Consequently, operational stability experiments showed that the protocol adopted to prepare the CS/CH/MNP nanoparticles had increased the durability of RML. The RML-CS/CH/MNP could catalyze up to eight successive esterification cycles to produce PeVa. The study also demonstrated the functionality of CS/CH/MNP nanoparticles as an eco-friendly support matrix for improving enzymatic activity and operational stability of RML to produce PeVa.
  19. Characterization, optimization and stability studies on Candida rugosa lipase supported on nanocellulose reinforced chitosan prepared from oil palm biomass
    Elias N, Chandren S, Razak FIA, Jamalis J, Widodo N, Wahab RA
    Int J Biol Macromol, 2018 Jul 15;114:306-316.
    PMID: 29578010 DOI: 10.1016/j.ijbiomac.2018.03.095
    The contribution of chitosan/nanocellulose (CS-NC) to the enzymatic activity of Candida rugosa lipase covalently bound on the surface of CS-NC (CRL/CS-NC) was investigated. Cellulosic material from oil palm frond leaves (OPFL) were bleached, alkaline treated and acid hydrolyzed to obtain the purified NC and used as nano-fillers in CS. XRD, Raman spectroscopy and optical fluorescence microscopic analyses revealed existence of strong hydrogen bonds between CS and the NC nanofillers. The CRLs were successfully conjugated to the surface of the CS-NC supports via imine bonds that occurred through a Schiff's based mechanism. Process parameters for the immobilization of CRL were assessed for factors temperature, concentration of glutaraldehyde and pH, to afford the highest enzyme activity to achieve maximum conversion of butyl butyrate within 3h of incubation. Conversion as high as 88% was reached under an optimized condition of 25°C, 0.3% glutaraldehyde concentration and buffer at pH7. Thermal stability of CRL/CS-NCs was 1.5-fold greater than that of free CRL, with biocatalysts reusability for up to 8 successive esterification cycles. This research provides a promising approach for expanding the use of NC from OPFL for enhancing enzyme activity in favour of an alternative eco-friendly means to synthesize butyl butyrate.
  20. Application of Box-Behnken design for ultrasound-assisted extraction and recycling preparative HPLC for isolation of anthraquinones from Cassia singueana
    Jibril S, Basar N, Sirat HM, Wahab RA, Mahat NA, Nahar L, et al.
    Phytochem Anal, 2019 Jan;30(1):101-109.
    PMID: 30288828 DOI: 10.1002/pca.2795
    INTRODUCTION: Cassia singueana Del. (Fabaceae) is a rare medicinal plant used in the traditional medicine preparations to treat various ailments. The root of C. singueana is a rich source of anthraquinones that possess anticancer, antibacterial and antifungal properties.

    OBJECTIVE: The objective of this study was to develop an ultrasound-assisted extraction (UAE) method for achieving a high extraction yield of anthraquinones using the response surface methodology (RSM), Box-Behnken design (BBD), and a recycling preparative high-performance liquid chromatography (HPLC) protocol for isolation of anthraquinones from C. singueana.

    METHODOLOGY: Optimisation of UAE was performed using the Box-Behnken experimental design. Recycling preparative HPLC was employed to isolate anthraquinones from the root extract of C. singueana.

    RESULTS: The BBD was well-described by a quadratic polynomial model (R2  = 0.9751). The predicted optimal UAE conditions for a high extraction yield were obtained at: extraction time 25.00 min, temperature 50°C and solvent-sample ratio of 10 mL/g. Under the predicted conditions, the experimental value (1.65 ± 0.07%) closely agreed to the predicted yield (1.64%). The obtained crude extract of C. singueana root was subsequently purified to afford eight anthraquinones.

    CONCLUSION: The extraction protocol described here is suitable for large-scale extraction of anthraquinones from plant extracts.

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