Publications by authors named "Chew Tin Lee"

20 Publications

  • Page 1 of 1

Uncovering the dynamics in global carbon dioxide utilization research: a bibliometric analysis (1995-2019).

Environ Sci Pollut Res Int 2020 Nov 16. Epub 2020 Nov 16.

School of Chemical and Energy Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, 81310, Skudai, Johor, Malaysia.

The anthropogenic emission of carbon dioxide (CO) into the atmosphere is recognized as the main contributor to global climate change. To date, scientists have developed various strategies, including CO utilization technologies, to reduce global carbon emissions. This paper presents the global scientific landscape of the CO utilization research from 1995 to 2019 based on a bibliometric analysis of 1875 publications extracted from Web of Science. The findings indicate a major increase in the number of publications and citations received from 2015 to 2019, denoting a fast-emerging research trend. The dynamics of global CO utilization research is partly driven by China's policies and research funding to promote low-carbon economic development. Applied Energy is recognized as a core journal in this research topic. The utilization of CO is a multidisciplinary topic that has progressed by multidimensional collaborations at the country and organizations levels, while the formation of co-authorship networks at the individual level is mostly influenced by the authors' affiliations. Keyword co-occurrence analysis reveals a rapid evolution in the CO utilization strategies from chemical fixation in carbonates and epoxides to pilot-scale testing of power-to-gas technologies in Europe and the USA. The development of efficient power-to-fuel technologies and biological utilization routes (using microalgae and bacteria) will probably be the next research priorities in CO utilization research.
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http://dx.doi.org/10.1007/s11356-020-11643-wDOI Listing
November 2020

Microplastics and nanoplastics in global food webs: A bibliometric analysis (2009-2019).

Mar Pollut Bull 2020 Sep 8;158:111432. Epub 2020 Jul 8.

School of Chemical and Energy Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia.

This paper presents the research landscape on microplastics and nanoplastics (M/NPs) in global food webs based on a bibliometric analysis of 330 publications published in 2009-2019 extracted from Web of Science. The publications increased tremendously since 2013. Marine Pollution Bulletin is one of the top productive journals for this topic. The publication landscape related to M/NPs in global food webs, as interdisciplinary research, is highly dependent on the funding availability. The high productivities of England, China, USA and European countries are attributed to the funding from the agencies at regional or national levels. Keyword analysis reveals the shift of research hotspots from investigations on M/NPs absorbed by various organisms in the ecosystems to studies on the trophic transfer of M/NPs and sorbed contaminants in the food webs and their associated adverse impacts. Funding agencies play important roles in leading the future development of this topic.
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http://dx.doi.org/10.1016/j.marpolbul.2020.111432DOI Listing
September 2020

Effect of aquaculture salinity on nitrification and microbial community in moving bed bioreactors with immobilized microbial granules.

Bioresour Technol 2020 Feb 14;297:122427. Epub 2019 Nov 14.

School of Environmental Science & Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. Electronic address:

The novel immobilized microbial granules (IMG) shows a significant effect of nitrification for freshwater aquaculture. However, there is lack of evaluation study on the performance of nitrification at high salinity due to the concentration of recycled water or seawater utilization. A laboratory scale moving bed bioreactor (MBBR) with IMG was tested on recycled synthetic aquaculture wastewater for the nitrification at 2.5 mg/L NH-N daily. The results indicated that IMG showed a high salinity tolerance and effectively converted ammonia to nitrate up to 92% at high salinity of 35.0 g/L NaCl. As salinity increased from near zero to 35.0 g/L, the microbial activity of nitrite oxidation bacteria (NOB) in the IMG decreased by 86.32%. The microbial community analysis indicated that salinity significantly influenced the community structure. It was found that Nitrosomonas sp. and Nitrospira sp. were the dominant genera for ammonia oxidation bacteria (AOB) and NOB respectively at different salinity levels.
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http://dx.doi.org/10.1016/j.biortech.2019.122427DOI Listing
February 2020

Environmental and economic feasibility of an integrated community composting plant and organic farm in Malaysia.

J Environ Manage 2019 Aug 29;244:431-439. Epub 2019 May 29.

Sustainable Process Integration Laboratory - SPIL, NETME Centre, Faculty of Mechanical Engineering, Brno University of Technology, - VUT Brno, Tachnická 2896/2, 616 00, Brno, Czech Republic.

Waste prevention and management become a significant issue worldwide to achieve sustainable development. Similar to many developing countries, Malaysia has faced severe problems in waste management due to its rapid economic growth and urbanisation. The municipal solid waste (MSW) production rate in Malaysia had increased significantly in a recent year, ranging from 0.8 to 1.25 kg/person∙d. The wastes generated contain a high amount of organic portion with high moisture content. Improper MSW management practice or delayed in waste collection and transportation can lead to severe health issues. This paper presents a case study in Johor Bahru, Malaysia (FOLO Farm), in which a composting prototype is used as the waste management technology to recycle the food and vegetable wastes. The greenhouse gases (GHG) mitigation and economic feasibility of the integrated composting and organic farming in this study are reported. This study showed a reduction of 27% of GHG by diverting the food and vegetable wastes from open dumping to the composting plant. Higher reduction rate (∼44%) can be achieved with better planning of waste collection route and applying the mitigation strategies during the composting process. By adapting the membership concept, this project not only ensures the economic feasibility of running a composting plant but also secures a channel for the growth of vegetable distribution. This study provides an insight into the feasibility and desirability to implement a pilot-scale composting for organic waste management to achieve the low carbon and self-sustain community.
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http://dx.doi.org/10.1016/j.jenvman.2019.05.050DOI Listing
August 2019

Raw oil palm frond leaves as cost-effective substrate for cellulase and xylanase productions by Trichoderma asperellum UC1 under solid-state fermentation.

J Environ Manage 2019 Aug 13;243:206-217. Epub 2019 May 13.

Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Malaysia; Enzyme Technology and Green Synthesis Group, Faculty of Science, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Malaysia. Electronic address:

Production of cellulases and xylanase by a novel Trichoderma asperellum UC1 (GenBank accession no. MF774876) under solid state fermentation (SSF) of raw oil palm frond leaves (OPFL) was optimized. Under optimum fermentation parameters (30 °C, 60-80% moisture content, 2.5 × 10 spores/g inoculum size) maximum CMCase, FPase, β-glucosidase and xylanase activity were recorded at 136.16 IU/g, 26.03 U/g, 130.09 IU/g and 255.01 U/g, respectively. Cellulases and xylanase were produced between a broad pH range of pH 6.0-12.0. The enzyme complex that comprised of four endo-β-1,4-xylanases and endoglucanases, alongside exoglucanase and β-glucosidase showed thermophilic and acidophilic characteristics at 50-60 °C and pH 3.0-4.0, respectively. Glucose (16.87 mg/g) and fructose (18.09 mg/g) were among the dominant sugar products from the in situ hydrolysis of OPFL, aside from cellobiose (105.92 mg/g) and xylose (1.08 mg/g). Thermal and pH stability tests revealed that enzymes CMCase, FPase, β-glucosidase and xylanase retained 50% residual activities for up to 15.18, 4.06, 17.47 and 15.16 h of incubation at 60 °C, as well as 64.59, 25.14, 68.59 and 19.20 h at pH 4.0, respectively. Based on the findings, it appeared that the unique polymeric structure of raw OPFL favored cellulases and xylanase productions.
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http://dx.doi.org/10.1016/j.jenvman.2019.04.113DOI Listing
August 2019

Anaerobic digestion of lignocellulosic waste: Environmental impact and economic assessment.

J Environ Manage 2019 Feb 24;231:352-363. Epub 2018 Oct 24.

Department of Bioprocess Engineering, Faculty of Chemical and Energy Engineering Universiti Teknologi Malaysia (UTM), 81310, UTM, Johor Bahru, Johor, Malaysia.

Lignocellulosic waste (LW) is abundant in availability and is one of the suitable substrates for anaerobic digestion (AD). However, it is a complex solid substrate matrix that hinders the hydrolysis stage of anaerobic digestion. This study assessed various pre-treatment and post-treatments of lignocellulosic waste for anaerobic digestion benefiting from advanced P-graph and GaBi software (Thinkstep, Germany) from the perspective of cost and environmental performances (global warming potential, human toxicity, ozone depletion potential, particulate matter, photochemical oxidant creation, acidification and eutrophication potential). CaO pre-treatment (P4), HS removal with membrane separation post-treatment (HSR MS) and without the composting of digestate is identified as the cost-optimal pathway. The biological (P7- Enzyme, P8- Microbial Consortium) and physical (P1- Grinding, P2- Steam Explosion, P3- Water Vapour) pre-treatments alternatives have lower environmental impacts than chemical pre-treatments (P4- CaO, P5- NaOH, P6- HSO) however they are not part of the near cost optimal solutions. For post-treatment, the near cost optimal alternatives are HS removal with organic physical scrubbing (HSR OPS) and HS removal with amine scrubbing (HSR AS). HSR AS has a better performance in the overall environmental impacts followed by HSR MS and HSR OPS. In general, the suggested cost-optimal solution is still having relatively lower environmental impacts and feasible for implementation (cost effective). There is very complicated to find a universal AD solution. Different scenarios (the type of substrate, the scale, product demand, policies) have different constraints and consequently solutions. The trade-offs between cost and environment performances should be a future extension of this work.
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http://dx.doi.org/10.1016/j.jenvman.2018.10.020DOI Listing
February 2019

Anaerobic digestion of municipal solid waste: Energy and carbon emission footprint.

J Environ Manage 2018 Oct 8;223:888-897. Epub 2018 Jul 8.

Centre for Process Integration, School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, M13 9PL, United Kingdom.

Anaerobic digestion (AD) serves as a promising alternative for waste treatment and a potential solution to improve the energy supply security. The feasibility of AD has been proven in some of the technologically and agriculturally advanced countries. However, development is still needed for worldwide implementation, especially for AD process dealing with municipal solid waste (MSW). This paper reviews various approaches and stages in the AD of MSW, which used to optimise the biogas production and quality. The assessed stages include pre-treatment, digestion process, post-treatment as well as the waste collection and transportation. The latest approaches and integrated system to improve the AD process are also presented. The stages were assessed in a relatively quantitative manner. The range of energy requirement, carbon emission footprint and the percentage of enhancement are summarised. Thermal hydrolysis pre-treatment is identified to be less suitable for MSW (-5% to +15.4% enhancement), unless conducted in the two-phase AD system. Microwave pre-treatment shows consistent performance in elevating the biogas production of MSW, but the energy consumption (114.24-8,040 kWh t) and carbon emission footprint (59.93-4,217.78 kg CO t waste) are relatively high. Chemical (∼0.43 kWh m) and membrane-based (∼0.45 kWh m) post-treatments are suggested to be a lower energy consumption approach for upgrading the biogas. The feasibility in terms of cost (scale up) and other environmental impacts (non-CO footprint) needs to be further assessed. This study provides an overview to facilitate further development and extended implementation of AD.
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http://dx.doi.org/10.1016/j.jenvman.2018.07.005DOI Listing
October 2018

Effects of different vermicompost extracts of palm oil mill effluent and palm-pressed fiber mixture on seed germination of mung bean and its relative toxicity.

Environ Sci Pollut Res Int 2018 Dec 17;25(36):35805-35810. Epub 2018 Apr 17.

Faculty of Environment and Energy, Science and Research Branch, Islamic Azad University, Tehran, Iran.

Several treatment technologies are available for the treatment of palm oil mill wastes. Vermicomposting is widely recognized as efficient, eco-friendly methods for converting organic waste materials to valuable products. This study evaluates the effect of different vermicompost extracts obtained from palm oil mill effluent (POME) and palm-pressed fiber (PPF) mixtures on the germination, growth, relative toxicity, and photosynthetic pigments of mung beans (Vigna radiata) plant. POME contains valuable nutrients and can be used as a liquid fertilizer for fertigation. Mung bean seeds were sown in petri dishes irrigated with different dilutions of vermicomposted POME-PPF extracts, namely 50, 60, and 70% at varying dilutions. Results showed that at lower dilutions, the vermicompost extracts showed favorable effects on seed germination, seedling growth, and total chlorophyll content in mung bean seedlings, but at higher dilutions, they showed inhibitory effects. The carotenoid contents also decreased with increased dilutions of POME-PPF. This study recommends that the extracts could serve as a good source of fertilizer for the germination and growth enhancement of mung bean seedlings at the recommended dilutions.
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http://dx.doi.org/10.1007/s11356-018-1875-8DOI Listing
December 2018

Evaluation of Effective Microorganisms on home scale organic waste composting.

J Environ Manage 2018 Jun 17;216:41-48. Epub 2017 Apr 17.

Department of Bioprocess Engineering, Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia (UTM), 81310, UTM Johor Bahru, Johor, Malaysia.

Home composting can be an effective way to reduce the volume of municipal solid waste. The aim of this study is to evaluate the effect of Effective Microorganism™ (EM) for the home scale co-composting of food waste, rice bran and dried leaves. A general consensus is lacking regarding the efficiency of inoculation composting. Home scale composting was carried out with and without EM (control) to identify the roles of EM. The composting parameters for both trials showed a similar trend of changes during the decomposition. As assayed by Fourier Transform Infrared Spectroscopy (FTIR), the functional group of humic acid was initially dominated by aliphatic structure but was dominated by the aromatic in the final compost. The EM compost has a sharper peak of aromatic CC bond presenting a better degree of humification. Compost with EM achieved a slightly higher temperature at the early stage, with foul odour suppressed, enhanced humification process and a greater fat reduction (73%). No significant difference was found for the final composts inoculated with and without EM. The properties included pH (∼7), electric conductivity (∼2), carbon-to-nitrogen ratio (C: N < 14), colour (dark brown), odour (earthy smell), germination index (>100%), humic acid content (4.5-4.8%) and pathogen content (no Salmonella, <1000 Most Probable Number/g E. coli). All samples were well matured within 2 months. The potassium and phosphate contents in both cases were similar however the EM compost has a higher nitrogen content (+1.5%). The overall results suggested the positive effect provided by EM notably in odour control and humification.
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http://dx.doi.org/10.1016/j.jenvman.2017.04.019DOI Listing
June 2018

Towards low carbon society in Iskandar Malaysia: Implementation and feasibility of community organic waste composting.

J Environ Manage 2017 Dec 3;203(Pt 2):679-687. Epub 2016 Jun 3.

Solid Waste Management Research Center, Graduate School of Environmental Science, Okayama University, Okayama, Japan.

Rapid population growth and urbanisation have generated large amount of municipal solid waste (MSW) in many cities. Up to 40-60% of Malaysia's MSW is reported to be food waste where such waste is highly putrescible and can cause bad odour and public health issue if its disposal is delayed. In this study, the implementation of community composting in a village within Iskandar Malaysia is presented as a case study to showcase effective MSW management and mitigation of GHG emission. The selected village, Felda Taib Andak (FTA), is located within a palm oil plantation and a crude palm oil processing mill. This project showcases a community-composting prototype to compost food and oil palm wastes into high quality compost. The objective of this article is to highlight the economic and environment impacts of a community-based composting project to the key stakeholders in the community, including residents, oil palm plantation owners and palm oil mill operators by comparing three different scenarios, through a life cycle approach, in terms of the greenhouse gas emission and cost benefit analysis. First scenario is the baseline case, where all the domestic waste is sent to landfill site. In the second scenario, a small-scale centralised composting project was implemented. In the third scenario, the data obtained from Scenario 2 was used to do a projection on the GHG emission and costing analysis for a pilot-scale centralised composting plant. The study showed a reduction potential of 71.64% on GHG emission through the diversion of food waste from landfill, compost utilisation and significant revenue from the compost sale in Scenario 3. This thus provided better insight into the feasibility and desirability in implementing a pilot-scale centralised composting plant for a sub-urban community in Malaysia to achieve a low carbon and self-sustainable society, in terms of environment and economic aspects.
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http://dx.doi.org/10.1016/j.jenvman.2016.05.033DOI Listing
December 2017

Physicochemical profile of microbial-assisted composting on empty fruit bunches of oil palm trees.

Environ Sci Pollut Res Int 2015 Dec 19;22(24):19814-22. Epub 2015 Aug 19.

Department of Bioprocess Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor Bahru, Johor, Malaysia.

This study was carried out to investigate the physicochemical properties of compost from oil palm empty fruit bunches (EFB) inoculated with effective microorganisms (EM∙1™). The duration of microbial-assisted composting was shorter (∼7 days) than control samples (2 months) in a laboratory scale (2 kg) experiment. The temperature profile of EFB compost fluctuated between 26 and 52 °C without the presence of consistent thermophilic phase. The pH of compost changed from weak acidic (pH ∼5) to mild alkaline (pH ∼8) because of the formation of nitrogenous ions such as ammonium (NH4 (+)), nitrite (NO2 (-)), and nitrate (NO3 (-)) from organic substances during mineralization. The pH of the microbial-treated compost was less than 8.5 which is important to prevent the loss of nitrogen as ammonia gas in a strong alkaline condition. Similarly, carbon mineralization could be determined by measuring CO2 emission. The microbial-treated compost could maintain longer period (∼13 days) of high CO2 emission resulted from high microbial activity and reached the threshold value (120 mg CO2-C kg(-1) day(-1)) for compost maturity earlier (7 days). Microbial-treated compost slightly improved the content of minerals such as Mg, K, Ca, and B, as well as key metabolite, 5-aminolevulinic acid for plant growth at the maturity stage of compost. Graphical Abstract Microbial-assisted composting on empty fruit bunches.
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http://dx.doi.org/10.1007/s11356-015-5156-5DOI Listing
December 2015

Edible Bird's nest extract as a chondro-protective agent for human chondrocytes isolated from osteoarthritic knee: in vitro study.

BMC Complement Altern Med 2013 Jan 22;13:19. Epub 2013 Jan 22.

Department of Physiology, University Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, Kuala Lumpur, Malaysia.

Background: Osteoarthritis (OA) is a degenerative joint disease that results in the destruction of cartilage. Edible Bird's Nest (EBN) extract contains important components, which can reduce the progression of osteoarthritis and helps in the regeneration of the cartilage. The present study aimed to investigate the effect of EBN extract on the catabolic and anabolic activities of the human articular chondrocytes (HACs) isolated from the knee joint of patients with OA.

Methods: A single batch of EBN extract was prepared with hot-water extraction and coded as HMG. HACs were isolated from the knee joint cartilage removed during surgery. The optimum concentration of HMG for HAC cultures was determined using MTT assay. The effect of HMG on the catabolic and anabolic genes' expression in HACs was measured by real-time PCR. The total amount of prostaglandin E2 (PGE2) production was determined by ELISA method, and the total sulphated glycosaminoglycan (GAGs) production was quantified by 1,9-dimethylmethylene blue (DMMB) assay.

Results: MTT assay showed 0.50% - 1.00% HMG supplementation promoted HACs proliferation. HMG supplementation was able to reduce the catabolic genes' expression in cultured HACs such as matrix metalloproteinases (MMP1 & MMP3), Interleukin 1, 6 and 8 (IL-1, IL-6 & IL-8), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). Prostaglandin E2 (PGE2) production was significantly reduced in HAC cultures supplemented with HMG. With regard to anabolic activity assessment, type II collagen, Aggrecan and SOX-9 gene expression as well as sGAG production was increased in the HMG supplemented groups.

Conclusion: Edible Bird's Nest extract coded as HMG demonstrated chondro-protection ability on human articular chondrocytes in vitro. It reduced catabolic activities and increased cartilage extracellular matrix synthesis. It is concluded that HMG is a potential agent in the treatment of osteoarthritis.
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http://dx.doi.org/10.1186/1472-6882-13-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3558384PMC
January 2013

Hydrolysis of virgin coconut oil using immobilized lipase in a batch reactor.

Enzyme Res 2012 16;2012:542589. Epub 2012 Aug 16.

Metabolites Profiling Laboratory, Institute of Bioproduct Development, Universiti Teknologi Malaysia, Johor, 81310 Johor Bahru, Malaysia.

Hydrolysis of virgin coconut oil (VCO) had been carried out by using an immobilised lipase from Mucor miehei (Lipozyme) in a water-jacketed batch reactor. The kinetic of the hydrolysis was investigated by varying the parameters such as VCO concentration, enzyme loading, water content, and reaction temperature. It was found that VCO exhibited substrate inhibition at the concentration more than 40% (v/v). Lipozyme also achieved the highest production of free fatty acids, 4.56 mM at 1% (w/v) of enzyme loading. The optimum water content for VCO hydrolysis was 7% (v/v). A relatively high content of water was required because water was one of the reactants in the hydrolysis. The progress curve and the temperature profile of the enzymatic hydrolysis also showed that Lipozyme could be used for free fatty acid production at the temperature up to 50°C. However, the highest initial reaction rate and the highest yield of free fatty acid production were at 45 and 40°C, respectively. A 100 hours of initial reaction time has to be compensated in order to obtain the highest yield of free fatty acid production at 40°C.
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http://dx.doi.org/10.1155/2012/542589DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3431091PMC
September 2012

Plant proteins, minerals and trace elements of Eurycoma longifolia (Tongkat Ali).

Nat Prod Res 2013 Mar 3;27(4-5):314-8. Epub 2012 Apr 3.

Metabolites Profiling Laboratory, Institute of Bioproduct Development, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia.

A water extraction method has been used to extract plant proteins from the roots of Eurycoma longifolia harvested from Perak and Pahang, Malaysia. On the basis of the spectroscopic Bradford assay, Tongkat Ali Perak and Pahang contained 0.3868 and 0.9573 mg mL(-1) of crude protein, respectively. The crude proteins were separated by one dimensional 15% sodium dodecyl sulphate polyacrylamide gel electrophoresis into two (49.8 and 5.5 kD) and four (49.8, 24.7, 21.1 and 5.5 kD) protein spots for Tongkat Ali Perak and Pahang, respectively. Isoleucine was present in the highest concentration significantly. Both plant samples showed differences in the mineral and trace element profiles, but the minerals calcium, magnesium and potassium were present in the highest concentration. The highly concerned toxic metals such as arsenic and lead were not detected.
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http://dx.doi.org/10.1080/14786419.2012.676552DOI Listing
March 2013

LC-MS/MS-based metabolites of Eurycoma longifolia (Tongkat Ali) in Malaysia (Perak and Pahang).

J Chromatogr B Analyt Technol Biomed Life Sci 2011 Dec 9;879(32):3909-19. Epub 2011 Nov 9.

Institute of Bioproduct Development, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia.

A number of three LC-MS/MS hybrid systems (QTof, TripleTof and QTrap) has been used to profile small metabolites (m/z 100-1000) and to detect the targeted metabolites such as quassinoids, alkaloids, triterpene and biphenylneolignans from the aqueous extracts of Eurycoma longifolia. The metabolite profiles of small molecules showed four significant clusters in the principle component analysis for the aqueous extracts of E. longifolia, which had been collected from different geographical terrains (Perak and Pahang) and processed at different extraction temperatures (35°C and 100°C). A small peptide of leucine (m/z 679) and a new hydroxyl methyl β-carboline propionic acid have been identified to differentiate E. longifolia extracts that prepared at 35°C and 100°C, respectively. From the targeted metabolites identification, it was found that 3,4ɛ-dihydroeurycomanone (quassinoids) and eurylene (squalene-type triterpene) could only be detected in the Pahang extract, whereas canthin-6-one-3N-oxide could only be detected in the Perak extract. Overall, quassinoids were present in the highest concentration, particularly eurycomanone and its derivatives compared to the other groups of metabolites. However, the concentration of canthin-6-one and β-carboline alkaloids was significantly increased when the roots of the plant samples were extracted at 100°C.
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http://dx.doi.org/10.1016/j.jchromb.2011.11.002DOI Listing
December 2011

Flavonoids and phenolic acids from Labisia pumila (Kacip Fatimah).

Food Chem 2011 Aug 1;127(3):1186-92. Epub 2011 Feb 1.

Metabolites Profiling Laboratory, Chemical Engineering Pilot Plant, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia.

Both total phenolic content (TPC) and total flavonoid content (TFC) of Labisia pumila extracts were determined spectrophotometrically. L. pumila leaves extracted in 60% methanol (MeOH) were fractionated on C18 cartridge and the antioxidant property of each fraction was determined by measuring free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity. The 40% MeOH fraction exhibited the highest scavenging activity. Nine flavonols (quercetin, myricetin and kaempferol), two flavanols (catechin and epigallocatechin) and nine phenolic acids were identified from this active fraction by UPLC-ESI-MS/MS, and confirmed by comparison with the mass spectra of standard aglycones, theoretical fragments generated from MS Fragmenter software, and literature values.
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http://dx.doi.org/10.1016/j.foodchem.2011.01.122DOI Listing
August 2011

Modeling of oscillatory bursting activity of pancreatic beta-cells under regulated glucose stimulation.

Mol Cell Endocrinol 2009 Aug 24;307(1-2):57-67. Epub 2009 Mar 24.

Faculty of Science, Engineering and Technology (FSET), Perak Campus, Universiti Tunku Abdul Rahman, Jalan Universiti, Perak, Malaysia.

A mathematical model to describe the oscillatory bursting activity of pancreatic beta-cells is combined with a model of glucose regulation system in this work to study the bursting pattern under regulated extracellular glucose stimulation. The bursting electrical activity in beta-cells is crucial for the release of insulin, which acts to regulate the blood glucose level. Different types of bursting pattern have been observed experimentally in glucose-stimulated islets both in vivo and in vitro, and the variations in these patterns have been linked to changes in glucose level. The combined model in this study enables us to have a deeper understanding on the regime change of bursting pattern when glucose level changes due to hormonal regulation, especially in the postprandial state. This is especially important as the oscillatory components of electrical activity play significant physiological roles in insulin secretion and some components have been found to be lost in type 2 diabetic patients.
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http://dx.doi.org/10.1016/j.mce.2009.03.005DOI Listing
August 2009

Modeling of glucose regulation and insulin-signaling pathways.

Mol Cell Endocrinol 2009 May 7;303(1-2):13-24. Epub 2009 Feb 7.

Department of Bioprocess Engineering, Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia.

A model of glucose regulation system was combined with a model of insulin-signaling pathways in this study. A feedback loop was added to link the transportation of glucose into cells (by GLUT4 in the insulin-signaling pathways) and the insulin-dependent glucose uptake in the glucose regulation model using the Michaelis-Menten kinetic model. A value of K(m) for GLUT4 was estimated using Genetic Algorithm. The estimated value was found to be 25.3 mM, which was in the range of K(m) values found experimentally from in vivo and in vitro human studies. Based on the results of this study, the combined model enables us to understand the overall dynamics of glucose at the systemic level, monitor the time profile of components in the insulin-signaling pathways at the cellular level and gives a good estimate of the K(m) value of glucose transportation by GLUT4. In conclusion, metabolic modeling such as displayed in this study provides a good predictive method to study the step-by-step reactions in an organism at different levels and should be used in combination with experimental approach to increase our understanding of metabolic disorders such as type 2 diabetes.
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http://dx.doi.org/10.1016/j.mce.2009.01.018DOI Listing
May 2009

Differential interactions of plasmid DNA, RNA and endotoxin with immobilised and free metal ions.

J Chromatogr A 2007 Feb 20;1141(2):226-34. Epub 2006 Dec 20.

Department of Chemical and Biomolecular Engineering, National University of Singapore, 10 Kent Ridge Crescent, 117576 Singapore.

Separation of negatively charged molecules, such as plasmid DNA (pDNA), RNA and endotoxin forms a bottleneck for the development of pDNA vaccine production process. The use of affinity interactions of transition metal ions with these molecules may provide an ideal separation methodology. In this study, the binding behaviour of pDNA, RNA and endotoxin to transition metal ions, either in immobilised or free form, was investigated. Transition metal ions: Cu2+, Ni2+, Zn2+, Co2+ and Fe3+, typically employed in the immobilised metal affinity chromatography (IMAC), showed very different binding behaviour depending on the type of metal ions and their existing state, i.e. immobilised or free. In the alkaline cell lysate, pDNA showed no binding to any of the IMAC chemistries tested whereas RNA interacted significantly with Cu2+-iminodiacetic acid (IDA) and Ni2+-IDA but showed no substantial binding to the rest of the IMAC chemistries. pDNA and RNA, however, interacted to varying degrees with free metal ions in the solution. The greatest selectivity in terms of pDNA and RNA separation was achieved with Zn2+ which enabled almost full precipitation of RNA while keeping pDNA soluble. For both immobilised and free metal ions, ionic strength of solution affected the metal ion-nucleic acid interaction significantly. Endotoxin, being more flexible, was able to interact better with the immobilised metal ions than the nucleic acids and showed binding to all the IMAC chemistries. The specific interactions of immobilised and/or free metal ions with pDNA, RNA and endotoxin showed a good potential, by selectively removing RNA and endotoxin at high efficiency, to develop a simplified pDNA purification process with improved process economics.
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http://dx.doi.org/10.1016/j.chroma.2006.12.023DOI Listing
February 2007

Combined in-fermenter extraction and cross-flow microfiltration for improved inclusion body processing.

Biotechnol Bioeng 2004 Jan;85(1):103-13

Department of Chemical Engineering, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom.

In this study we demonstrate a new in-fermenter chemical extraction procedure that degrades the cell wall of Escherichia coli and releases inclusion bodies (IBs) into the fermentation medium. We then prove that cross-flow microfiltration can be used to remove 91% of soluble contaminants from the released IBs. The extraction protocol, based on a combination of Triton X-100, EDTA, and intracellular T7 lysozyme, effectively released most of the intracellular soluble content without solubilising the IBs. Cross-flow microfiltration using a 0.2 microm ceramic membrane successfully recovered the granulocyte macrophage-colony stimulating factor (GM-CSF) IBs with removal of 91% of the soluble contaminants and virtually no loss of IBs to the permeate. The filtration efficiency, in terms of both flux and transmission, was significantly enhanced by in-fermenter Benzonase digestion of nucleic acids following chemical extraction. Both the extraction and filtration methods exerted their efficacy directly on a crude fermentation broth, eliminating the need for cell recovery and resuspension in buffer. The processes demonstrated here can all be performed using just a fermenter and a single cross-flow filtration unit, demonstrating a high level of process intensification. Furthermore, there is considerable scope to also use the microfiltration system to subsequently solubilise the IBs, to separate the denatured protein from cell debris, and to refold the protein using diafiltration. In this way refolded protein can potentially be obtained, in a relatively pure state, using only two unit operations.
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http://dx.doi.org/10.1002/bit.10878DOI Listing
January 2004