Displaying publications 1 - 20 of 36 in total

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  1. Valorization of Dacryodes rostrata fruit through the characterization of its oil
    Tee LH, Yang B, Tey BT, Chan ES, Azlan A, Ismail A, et al.
    Food Chem, 2017 Nov 15;235:257-264.
    PMID: 28554634 DOI: 10.1016/j.foodchem.2017.05.021
    Dacryodes rostrata (kembayau) is an important food and oil resource for local communities in Borneo, but it is not commonly known to wider community. The objective of this work is to valorize kembayau fruit by evaluating the characteristics of the oil from the fruit. In this study, the physicochemical characteristics and the lipophilic essential nutrient; the fatty acid composition, vitamin E and beta-carotene content of oils obtained from the peel, pulp and seeds of kembayau fruits were studied. The pulp of the kembayau fruit contained highest proportion of oil, followed by peel and seed. Kembayau fruit contained vitamin E and had trace amount of beta-carotene. Besides, kembayau fruit oils were not toxic to BRL3A cells, provided hepatoprotection and reversed lipid peroxidation in paracetamol-induced toxicity. Our results suggest that kembayau can be a potential source for cooking oil as the physicochemical characteristics are comparable with commercial source such as oil palm.
  2. Underutilised palm stearin as hard stock for deep-frying medium and its performance for oil uptake in instant noodles
    Ooi EZH, Ab Karim NA, Chan ES, Wang Y, Tang TK, Tong SC, et al.
    J Sci Food Agric, 2024 May;104(7):3958-3970.
    PMID: 38284502 DOI: 10.1002/jsfa.13278
    BACKGROUND: As a by-product of the palm oil industry, palm stearin is often overlooked despite having several beneficial properties, such as excellent stability, which is critically essential to meet the demand of the global food trend in producing safer processed food. Specifically, deep frying of food is often associated with the production of toxic compounds that could potentially migrate into the food system when oils are degraded under continuous heating. The incorporation of palm stearin is regarded as a cost-effective and efficient method to modify the fatty acid composition of oils, enhance the frying qualities and lower the degradation rate.

    RESULTS: This study blended 5% and 10% palm stearin into palm oil to investigate the deep-frying performance and impact on food quality. Increasing the palm stearin content improved the frying oil's oxidative and hydrolytic stability, evidenced by reduction of total polar material, free fatty acid and total oxidation value. Addition of palm stearin increased the slip melting point which improved the oil's oxidative stability but no significant increase in oil content of instant noodles was observed. Scanning electron microscopy and fluorescence microscopy showed the formation of larger pores in the noodle structure that facilitated oil retention.

    CONCLUSION: Blending palm stearin into frying oil enhanced the frying stability and minimally affected the oil uptake in instant noodles. This article presents the viability of blending palm stearin into frying oils to develop longer-lasting frying oils. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

  3. Fulltext Towards an alcohol-free process for the production of palm phytonutrients via enzymatic hydrolysis of crude palm oil using liquid lipases
    Adiiba SH, Chan ES, Lee YY, Amelia, Chang MY, Song CP
    J Sci Food Agric, 2022 Dec;102(15):6921-6929.
    PMID: 35662022 DOI: 10.1002/jsfa.12053
    BACKGROUND: Crude palm oil (CPO) is rich with phytonutrients such as carotenoids and tocols which possesses many health benefits. The aim of this research was to develop a methanol-free process to produce palm phytonutrients via enzymatic hydrolysis. In this work, triacylglycerol was hydrolyzed into free fatty acids (FFAs) using three different types of liquid lipases derived from Aspergillus oryzae (ET 2.0), Aspergillus niger (Habio) and Candida antartica (CALB).

    RESULTS: ET 2.0 was found to be the best enzyme for hydrolysis. Under the optimum condition, the FFA content achievable was 790 g kg-1 after 24 h of reaction with 1:1 water-to-oil mass ratio at 50 °C and stirring speed of 9 × g. Furthermore, with the addition of 2 g kg-1 ascorbic acid, it was found that 98% of carotenoids and 96% of tocols could be retained after hydrolysis.

    CONCLUSION: This work shows that enzymatic hydrolysis, which is inherently safer, cleaner and sustainable is feasible to replace the conventional methanolysis for the production of palm phytonutrients. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

  4. Thermo-responsive adsorbent for size-selective protein adsorption
    Lee MF, Chan ES, Tam KC, Tey BT
    J Chromatogr A, 2015 May 15;1394:71-80.
    PMID: 25836051 DOI: 10.1016/j.chroma.2015.03.034
    A thermo-responsive random copolymer, POEGMA (poly(oligoethylene glycol) methacrylate) grafted on cationized agarose adsorbent was used for size selective protein adsorption. The effects of OEGMA300 ((oligoethylene glycol) methyl ether methacrylate, Mn=300g/mol) content and temperature on the adsorption of bovine serum albumin (BSA) were evaluated. Increasing the content of OEGMA300 resulted a reduction in BSA adsorption due to the enhanced shielding effect of OEGMA300 chains. Grafting of POEGMA chains onto cationized agarose adsorbent reduced the BSA adsorption by more than 95% at 26.5°C, which is below the LCST (lower critical solution temperature) of POEGMA. The BSA adsorption capacities for adsorbents grafted with 10 and 20mol% of OEGMA300 decreased by 48% and 46% respectively at 38°C, a temperature higher than their LCSTs. The temperature-dependent adsorption of BSA on the adsorbents was attributed to changes in the polymer conformation. The thermal transition of grafted POEGMA conformation exposed the ligand when the temperature was increased. Myoglobin (Myo), which was smaller than BSA, its adsorption behavior was less dependent on the polymer conformation. The adsorption of myoglobin onto the adsorbent with and without POEGMA showed similar percentage of reduction whereas the adsorption of BSA onto the adsorbent with POEGMA decreased by 7.6 times compared to the one without POEGMA. The packed bed of POEGMA grafted adsorbent was used for flow through separation of a protein mixture consisted of virus-like particle, Hepatitis B virus-like particle (HBVLP), BSA and insulin aspart. The recovery of HBVLP in 20mol% of OEGMA300 grafted adsorbent was increased by 19% compared to ungrafted adsorbent. The flow through of BSA can be reduced by increasing the operating temperature above LCST of 20mol% of OEGMA300 while the smaller protein, insulin aspart, remained adsorbed onto the cationized surface. Hence, this thermo-responsive adsorbent has a potential for size-selective separation of protein especially for the recovery of large biomolecule.
  5. Surgical training for anatomical endoscopic enucleation of the prostate
    Teoh JY, Cho CL, Wei Y, Isotani S, Tiong HY, Ong TA, et al.
    Andrologia, 2020 Sep;52(8):e13708.
    PMID: 32557751 DOI: 10.1111/and.13708
    Anatomical endoscopic enucleation of the prostate has been proposed as a potentially superior benign prostatic hyperplasia surgery than conventional transurethral resection of prostate. However, the learning curve of the procedure is steep, hence limiting its generalisability worldwide. In order to overcome the learning curve, a proper surgical training is extremely important. This review article discussed about various aspects of surgical training in anatomical endoscopic enucleation of the prostate. In summary, no matter what surgical technique or energy modality you use, the principle of anatomical enucleation should be followed. When one starts to perform prostate enucleation, a 50 to 80 g prostate appears to be the 'best case' to begin with. Mentorship is extremely important to shorten the learning curve and to prevent drastic complications from the procedure. A proficiency-based progression training programme with the use of simulation and training models should be the best way to teach and learn about prostate enucleation. Enucleation ratio efficacy is the preferred measure for assessing skill level and learning curve of prostate enucleation. Morcellation efficiency is commonly used to assess morcellation performance, but the importance of safety rather than efficiency must be emphasised.
  6. Fulltext Stabilization and Release of Palm Tocotrienol Emulsion Fabricated Using pH-Sensitive Calcium Carbonate
    Tan PY, Tey BT, Chan ES, Lai OM, Chang HW, Tan TB, et al.
    Foods, 2021 Feb 07;10(2).
    PMID: 33562391 DOI: 10.3390/foods10020358
    Calcium carbonate (CaCO3) has been utilized as a pH-responsive component in various products. In this present work, palm tocotrienols-rich fraction (TRF) was successfully entrapped in a self-assembled oil-in-water (O/W) emulsion system by using CaCO3 as the stabilizer. The emulsion droplet size, viscosity and tocotrienols entrapment efficiency (EE) were strongly affected by varying the processing (homogenization speed and time) and formulation (CaCO3 and TRF concentrations) parameters. Our findings indicated that the combination of 5000 rpm homogenization speed, 15 min homogenization time, 0.75% CaCO3 concentration and 2% TRF concentration resulted in a high EE of tocotrienols (92.59-99.16%) and small droplet size (18.83 ± 1.36 µm). The resulting emulsion system readily released the entrapped tocotrienols across the pH range tested (pH 1-9); with relatively the highest release observed at pH 3. The current study presents a potential pH-sensitive emulsion system for the entrapment and delivery of palm tocotrienols.
  7. Spray-dried alginate-coated Pickering emulsion stabilized by chitosan for improved oxidative stability and in vitro release profile
    Surjit Singh CK, Lim HP, Tey BT, Chan ES
    Carbohydr Polym, 2021 Jan 01;251:117110.
    PMID: 33142647 DOI: 10.1016/j.carbpol.2020.117110
    The commercial application of liquid-state Pickering emulsions in food systems remains a major challenge. In this study, we developed a spray-dried Pickering emulsion powder using chitosan as a Pickering emulsifier and alginate as a coating material. The functionality of the powder was evaluated in terms of its oxidative stability, pH-responsiveness, mucoadhesivity, and lipid digestibility. The Pickering emulsion powder was oxidatively more stable than the conventional emulsion powder stabilized by gum Arabic. The powder exhibited pH-responsiveness, whereby it remained intact in acidic pH, but dissolved to release the emulsion in 'Pickering form' at near-neutral pH. The Pickering emulsion powder was also mucoadhesive and could be digested by lipase in a controlled manner. These findings suggested that the multi-functional Pickering emulsion powder could be a potential delivery system for applications in the food industry.
  8. Size-selective purification of hepatitis B virus-like particle in flow-through chromatography: Types of ion exchange adsorbent and grafted polymer architecture
    Ng HW, Lee MFX, Chua GK, Gan BK, Tan WS, Ooi CW, et al.
    J Sep Sci, 2018 May;41(10):2119-2129.
    PMID: 29427396 DOI: 10.1002/jssc.201700823
    Hepatitis B virus-like particles expressed in Escherichia coli were purified using anion exchange adsorbents grafted with polymer poly(oligo(ethylene glycol) methacrylate) in flow-through chromatography mode. The virus-like particles were selectively excluded, while the relatively smaller sized host cell proteins were absorbed. The exclusion of virus-like particles was governed by the accessibility of binding sites (the size of adsorbents and the charge of grafted dextran chains) as well as the architecture (branch-chain length) of the grafted polymer. The branch-chain length of grafted polymer was altered by changing the type of monomers used. The larger adsorbent (90 μm) had an approximately twofold increase in the flow-through recovery, as compared to the smaller adsorbent (30 μm). Generally, polymer-grafted adsorbents improved the exclusion of the virus-like particles. Overall, the middle branch-chain length polymer grafted on larger adsorbent showed optimal performance at 92% flow-through recovery with a purification factor of 1.53. A comparative study between the adsorbent with dextran grafts and the polymer-grafted adsorbent showed that a better exclusion of virus-like particles was achieved with the absorbent grafted with inert polymer. The grafted polymer was also shown to reduce strong interaction between binding sites and virus-like particles, which preserved the particles' structure.
  9. Fulltext Recent development and challenges in extraction of phytonutrients from palm oil
    Hoe BC, Chan ES, Nagasundara Ramanan R, Ooi CW
    Compr Rev Food Sci Food Saf, 2020 11;19(6):4031-4061.
    PMID: 33337051 DOI: 10.1111/1541-4337.12648
    Phytonutrients are plant-derived bioactives which are widely utilized as colorants or supplements in food, cosmetic, and pharmaceutical products. To meet the global demand for phytonutrients, oil palm has emerged as a promising source of phytonutrients on account of its large-scale plantation worldwide and high oil productivity. Phytonutrients including carotenoids, tocols, sterols, squalene, phospholipids, coenzyme Q10, and polyphenols can be found in crude palm oil as well as in the byproducts (e.g. palm oil mill effluent and palm-pressed fiber oil) generated from the palm oil milling process. However, the high viscosity and semisolid properties of palm oil are problematic in phytonutrient extraction. Another major challenge is the retention of the sensitive phytonutrients during the extraction process. Over the years, the advances in the extraction methods have improved the extractability of phytonutrients. The emerging extraction methods can operate under mild conditions to mitigate the risk of phytonutrient degradation. This review outlines the types of phytonutrient in palm oil and their extraction strategies. The working principles and operating conditions of extraction methods are discussed along with their potential and limitations in terms of extraction efficiency and practicability. The methods for pretreatment of feedstocks for improving extraction efficiency are also highlighted. The challenges in the extraction of phytonutrient from palm oil feedstock are summarized. Lastly, we provide suggestions for overcoming the limitations and improving the performances of phytonutrient extraction.
  10. Recent advances of characterization techniques for the formation, physical properties and stability of Pickering emulsion
    Low LE, Siva SP, Ho YK, Chan ES, Tey BT
    Adv Colloid Interface Sci, 2020 Mar;277:102117.
    PMID: 32035999 DOI: 10.1016/j.cis.2020.102117
    Recently, there have been increasing demand for the application of Pickering emulsions in various industries due to its combined advantage in terms of cost, quality and sustainability. This review aims to provide a complete overview of the available methodology for the physical characterization of emulsions that are stabilized by solid particles (known as Pickering emulsion). Current approaches and techniques for the analysis of the formation and properties of the Pickering emulsion were outlined along with the expected results of these methods on the emulsions. Besides, the application of modelling techniques has also been elaborated for the effective characterization of Pickering emulsions. Additionally, approaches to assess the stability of Pickering emulsions against physical deformation such as coalescence and gravitational separation were reviewed. Potential future developments of these characterization techniques were also briefly discussed. This review can act as a guide to researchers to better understand the standard procedures of Pickering emulsion assessment and the advanced methods available to date to study these emulsions, down to the minute details.
  11. Production of biodiesel using immobilized lipase--a critical review
    Jegannathan KR, Abang S, Poncelet D, Chan ES, Ravindra P
    Crit Rev Biotechnol, 2008;28(4):253-64.
    PMID: 19051104 DOI: 10.1080/07388550802428392
    Increase in volume of biodiesel production in the world scenario proves that biodiesel is accepted as an alternative to conventional fuel. Production of biodiesel using alkaline catalyst has been commercially implemented due to its high conversion and low production time. For the product and process development of biodiesel, enzymatic transesterification has been suggested to produce a high purity product with an economic, environment friendly process at mild reaction conditions. The enzyme cost being the main hurdle can be overcome by immobilization. Immobilized enzyme, which has been successfully used in various fields over the soluble counterpart, could be employed in biodiesel production with the aim of reducing the production cost by reusing the enzyme. This review attempts to provide an updated compilation of the studies reported on biodiesel production by using lipase immobilized through various techniques and the parameters, which affect their functionality.
  12. Prediction models for shape and size of ca-alginate macrobeads produced through extrusion-dripping method
    Chan ES, Lee BB, Ravindra P, Poncelet D
    J Colloid Interface Sci, 2009 Oct 1;338(1):63-72.
    PMID: 19604515 DOI: 10.1016/j.jcis.2009.05.027
    The aim of this work was to develop prediction models for shape and size of ca-alginate macrobeads produced through extrusion-dripping method. The relationship between the process variables on the shape and size of the alginate drops before and after gelation was established with the aid of image analysis. The results show that a critical Ohnersorge number (Oh)>0.24 was required to form spherical beads. The shape transition of ca-alginate beads could be typically distinguished into three phases along the collecting distance and it was affected by the combined influence of the solution properties, the collecting distance and the drop size. Mathematical equations and a master shape diagram were developed to reveal a clear operating region and the overall process limits within which spherical ca-alginate beads could be formed. In terms of bead size, the overall size correction factor (K) which accounted for the liquid loss factor (k(LF)) and the shrinkage factor (k(SF)), varied between 0.73 and 0.85 under the experimental conditions. The size prediction model correlated well with the experimental data. The approach and the outcome could be used as a model to develop prediction tools for similar bead production systems.
  13. Pickering emulsion-templated ionotropic gelation of tocotrienol microcapsules: effects of alginate and chitosan concentrations and gelation process parameters
    Tan PY, Tan TB, Chang HW, Mwangi WW, Tey BT, Chan ES, et al.
    J Sci Food Agric, 2021 Nov;101(14):5963-5971.
    PMID: 33840091 DOI: 10.1002/jsfa.11249
    BACKGROUND: Throughout the past decade, Pickering emulsion has been increasingly utilized for the encapsulation of bioactive compounds due to its high stability and biocompatibility. In the present work, palm tocotrienols were initially encapsulated in a calcium carbonate Pickering emulsion, which was then subjected to alginate gelation and subsequent chitosan coating. The effects of wall material (alginate and chitosan) concentrations, gelation pH and time, and chitosan coating time on the encapsulation efficiency of palm tocotrienols were explored.

    RESULTS: Our findings revealed that uncoated alginate microcapsules ruptured upon drying and exhibited low encapsulation efficiency (13.81 ± 2.76%). However, the addition of chitosan successfully provided a more complex and rigid external wall structure to enhance the stability of the microcapsules. By prolonging the crosslinking time from 5 to 30 min and increasing the chitosan concentration from 0.1% to 0.5%, the oil encapsulation efficiency was increased by 28%. Under the right gelation pH (pH 4), the extension of gelation time from 1 to 12 h resulted in an increase in alginate-Ca2+ crosslinkings, thus strengthening the microcapsules.

    CONCLUSION: With the optimum formulation and process parameters, a high encapsulation efficiency (81.49 ± 1.75%) with an elevated oil loading efficiency (63.58 ± 2.96%) were achieved. The final product is biocompatible and can potentially be used for the delivery of palm tocotrienols. © 2021 Society of Chemical Industry.

  14. Fulltext Physicochemical and antioxidative properties of ultrasound-assisted extraction of mahua (Madhuca longifolia) seed oil in comparison with conventional Soxhlet and mechanical extractions
    Thilakarathna RCN, Siow LF, Tang TK, Chan ES, Lee YY
    Ultrason Sonochem, 2023 Jan;92:106280.
    PMID: 36587443 DOI: 10.1016/j.ultsonch.2022.106280
    Ultrasound-assisted solvent extraction (UAE) was applied to extract underutilized Madhuca longifolia seed oil. The effect of extraction time, temperature, solvent type, solvent/sample ratio, and amplitude on the oil yield and recovery were investigated. Approximately 56.97% of oil yield and 99.54% of oil recovery were attained using mild conditions of 35 min, 35 °C, 40% amplitude, isopropanol to acetone (1:1), and solvent to sample (20 mL/g). UAE oil yield and recovery were comparable with Soxhlet extraction (SXE) whilst mechanical pressing (ME) yielded 
  15. Particle designs for the stabilization and controlled-delivery of protein drugs by biopolymers: a case study on insulin
    Lim HP, Tey BT, Chan ES
    J Control Release, 2014 Jul 28;186:11-21.
    PMID: 24816070 DOI: 10.1016/j.jconrel.2014.04.042
    Natural biopolymers have attracted considerable interest for the development of delivery systems for protein drugs owing to their biocompatibility, non-toxicity, renewability and mild processing conditions. This paper offers an overview of the current status and future perspectives of particle designs using biopolymers for the stabilization and controlled-delivery of a model protein drug--insulin. We first describe the design criteria for polymeric encapsulation and subsequently classify the basic principles of particle fabrication as well as the existing particle designs for oral insulin encapsulation. The performances of these existing particle designs in terms of insulin stability and in vitro release behavior in acidic and alkaline media, as well as their in vivo performance are compared and reviewed. This review forms the basis for future works on the optimization of particle design and material formulation for the development of an improved oral delivery system for protein drugs.
  16. Palm olein-in-water Pickering emulsion stabilized by Fe3O4-cellulose nanocrystal nanocomposites and their responses to pH
    Low LE, Tey BT, Ong BH, Chan ES, Tang SY
    Carbohydr Polym, 2017 Jan 02;155:391-399.
    PMID: 27702526 DOI: 10.1016/j.carbpol.2016.08.091
    We studied the formation of palm olein-in-water (O/W) Pickering emulsion stabilized by Fe3O4-cellulose nanocrystals (MCNC) nanocomposites obtained by ultrasound assisted in-situ co-precipitation method. The synthesized MCNC nanocomposites successfully stabilized Pickering emulsion with dual responses. The magnetic tests revealed a direct-relation between attractability of MCNC-stabilized Pickering emulsions and the emulsion droplet diameter. The Pickering emulsions were stable under pH ranging from 3 to 6. The stability substantially reduced around pH 8-10, and regained slowly when approaching pH 13. From microscopic and mastersizer analysis, monodisperse emulsion droplets were noticed at pH 3-6, and 13, while polydisperse emulsion were obtained at pH 8-12. The Pickering emulsions prepared at pH 6 are stable up to 14 days, while Pickering emulsions at pH 8 experienced coalescence. In this study, the dual stimuli-responsive Pickering emulsion stabilized by MCNC may hold potentials for biomedical and drug delivery as new generation of smart nanotherapeutic carrier.
  17. Over-expression of the X-linked inhibitor of apoptosis protein (XIAP) delays serum deprivation-induced apoptosis in CHO-K1 cells
    Liew JC, Tan WS, Alitheen NB, Chan ES, Tey BT
    J Biosci Bioeng, 2010 Sep;110(3):338-44.
    PMID: 20547346 DOI: 10.1016/j.jbiosc.2010.02.017
    Serum deprivation inhibits cell growth and initiates apoptosis cell death in mammalian cell cultures. Since apoptosis is a genetically controlled cell death pathway, over-expression of anti-apoptotic proteins may provide a way to delay apoptosis. This study investigated the ability of the X-linked inhibitor of apoptosis protein (XIAP) to inhibit apoptosis induced by serum deprivation. Study includes evaluation of the ability of XIAP to prolong culture period and its effect on cell proliferation in serum-deprived media. The full length human XIAP was introduced into CHO-K1 cell lines and the effects of XIAP over-expression on the inhibition of apoptosis induced by serum-deprived conditions were examined. In batch cultures, cells over-expressing XIAP showed decreased levels of apoptosis and a higher number of viable cell under serum-deprived conditions compared to the control cell lines. The viability of control cells dropped to 40% after 2days of serum deprivation, the XIAP expressing cells still maintained at a viability higher than 90%. Further investigation revealed that the caspase-3 activity of the CHO-K1 cell line was inhibited as a result of XIAP expression.
  18. Nutritional compositions and bioactivities of Dacryodes species: a review
    Tee LH, Yang B, Nagendra KP, Ramanan RN, Sun J, Chan ES, et al.
    Food Chem, 2014 Dec 15;165:247-55.
    PMID: 25038673 DOI: 10.1016/j.foodchem.2014.05.084
    Dacryodes species are evergreen, perennial trees with fleshy fruits and belong to the family Buseraseae. Many Dacryodes species are underutilized but are widely applied in traditional folk medicine to treat malaria, fever and skin diseases. The nutritional compositions, phytochemicals and biological activities of Dacryodes edulis, Dacryodes rostrata, Dacryodes buettneri, Dacryodes klaineana and Dacryodes hexandra are presented. The edible fruits of D. edulis are rich in lipids, proteins, vitamins, fatty acids and amino acids. Its extracts (leaf, fruit and resin) exhibit antioxidant, anti-microbial, anti-carcinogenic and other bioactivities. D. rostrata fruit has significant nutrient content, and is rich in proteins, lipids and minerals. These fruits are also highly rich in polyphenols, anthocyanins and antioxidant activities. This comprehensive review will assist the reader in understanding the nutritional benefits of Dacryodes species and in identifying current research needs.
  19. Nozzleless Fabrication of Oil-Core Biopolymeric Microcapsules by the Interfacial Gelation of Pickering Emulsion Templates
    Leong JY, Tey BT, Tan CP, Chan ES
    ACS Appl Mater Interfaces, 2015 Aug 5;7(30):16169-76.
    PMID: 26148344 DOI: 10.1021/acsami.5b04486
    Ionotropic gelation has been an attractive method for the fabrication of biopolymeric oil-core microcapsules due to its safe and mild processing conditions. However, the mandatory use of a nozzle system to form the microcapsules restricts the process scalability and the production of small microcapsules (<100 μm). We report, for the first time, a nozzleless and surfactant-free approach to fabricate oil-core biopolymeric microcapsules through ionotropic gelation at the interface of an O/W Pickering emulsion. This approach involves the self-assembly of calcium carbonate (CaCO3) nanoparticles at the interface of O/W emulsion droplets followed by the addition of a polyanionic biopolymer into the aqueous phase. Subsequently, CaCO3 nanoparticles are dissolved by pH reduction, thus liberating Ca(2+) ions to cross-link the surrounding polyanionic biopolymer to form a shell that encapsulates the oil droplet. We demonstrate the versatility of this method by fabricating microcapsules from different types of polyanionic biopolymers (i.e., alginate, pectin, and gellan gum) and water-immiscible liquid cores (i.e., palm olein, cyclohexane, dichloromethane, and toluene). In addition, small microcapsules with a mean size smaller than 100 μm can be produced by selecting the appropriate conventional emulsification methods available to prepare the Pickering emulsion. The simplicity and versatility of this method allows biopolymeric microcapsules to be fabricated with ease by ionotropic gelation for numerous applications.
  20. Negative chromatography purification of hepatitis B virus-like particles using poly(oligo(ethylene glycol) methacrylate) grafted cationic adsorbent
    Lee MF, Chan ES, Tan WS, Tam KC, Tey BT
    J Chromatogr A, 2015 Oct 9;1415:161-5.
    PMID: 26358561 DOI: 10.1016/j.chroma.2015.08.056
    Poly(oligo(ethylene glycol) methacrylate) (POEGMA), an inert polymer was grafted onto an anion exchange adsorbent for the exclusion of relatively larger hepatitis B virus-like particles (HB-VLPs) from the anion exchange ligand (Q) and at the same time this process allowed the selective adsorption of smaller size Escherichia coli host cell proteins (HCPs). The chain lengths of the POEGMA grafted were modulated by varying the amount of monomers used in the polymer grafting. The purification factor and yield of the HB-VLPs obtained from the flow-through of negative chromatography were 2.3 and 66.0±3.1%, respectively, when shorter chain length of POEGMA (SQ) was grafted. Adsorbent grafted with longer chain of POEGMA (LQ) excluded some HCPs that are larger in size together with the HB-VLPs, reducing the purity of the recovered HB-VLPs. Further heat-treatment of the flow-through pool from SQ followed by centrifugation increased the purity of heat stable HB-VLPs to 87.5±1.1%. Heat-treatment of the flow through sample resulted in thermal denaturation and aggregation of HCPs, while the heat stable HB-VLPs still remained intact as observed under a transmission electron microscope. The performance of the negative chromatography together with heat treatment in the purification of HB-VLPs is far better than the reported bind-and-elute techniques.
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