Displaying publications 1 - 20 of 95 in total

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  1. When paediatric facial nerve paralysis is not a Bell's palsy: A case of cerebellopontine angle tumour
    Ismail MT, Rahman RA, Idris NS
    J Taibah Univ Med Sci, 2022 Feb;17(1):141-145.
    PMID: 35140576 DOI: 10.1016/j.jtumed.2021.08.008
    Facial nerve paralysis in children is a rare clinical condition that can lead to serious complications. Due to their rare occurrence, tumours, especially in the cerebellopontine angle, may be overlooked. We report a case of cerebellopontine angle tumour in an 8-year-old boy who presented with a right-sided lower motor neuron type of facial nerve palsy. Further examination showed a mild bilateral nystagmus. However, misled by the initial diagnosis of Bell's palsy, there was a delay in performing diagnostic magnetic resonance imaging of the brain, which showed a large mass in the cerebellopontine. Subsequently, six weeks after his initial presentation, the boy succumbed to the disease. This case illustrates that careful clinical examination, even in a seemingly simple case, is imperative to avoid diagnostic errors.
  2. Fulltext Warpage Optimisation Using Recycled Polycar-bonates (PC) on Front Panel Housing
    Tamizi NAMA, Rahim SZA, Abdellah AE, Abdullah MMAB, Nabiałek M, Wysłocki JJ, et al.
    Materials (Basel), 2021 Mar 15;14(6).
    PMID: 33804036 DOI: 10.3390/ma14061416
    Many studies have been done using recycled waste materials to minimise environmental problems. It is a great opportunity to explore mechanical recycling and the use of recycled and virgin blend as a material to produce new products with minimum defects. In this study, appropriate processing parameters were considered to mould the front panel housing part using R0% (virgin), R30% (30% virgin: 70% recycled), R40% (40% virgin: 60% recycled) and R50% (50% virgin: 50% recycled) of Polycarbonate (PC). The manufacturing ability and quality during preliminary stage can be predicted through simulation analysis using Autodesk Moldflow Insight 2012 software. The recommended processing parameters and values of warpage in x and y directions can also be obtained using this software. No value of warpage was obtained from simulation studies for x direction on the front panel housing. Therefore, this study only focused on reducing the warpage in the y direction. Response Surface Methodology (RSM) and Genetic Algorithm (GA) optimisation methods were used to find the optimal processing parameters. As the results, the optimal ratio of recycled PC material was found to be R30%, followed by R40% and R50% materials using RSM and GA methods as compared to the average value of warpage on the moulded part using R0%. The most influential processing parameter that contributed to warpage defect was packing pressure for all materials used in this study.
  3. Uterine-conserving approach in ruptured intramyometrial ectopic pregnancy
    Esther LSY, Chew KT, Rahman RA, Zainuddin AA, Hing EY, Kampan N
    Horm Mol Biol Clin Investig, 2020 Mar 13;41(2).
    PMID: 32167930 DOI: 10.1515/hmbci-2020-0001
    Intramyometrial ectopic pregnancy (IMEP) is a rare form of ectopic pregnancy. It is defined as a conceptus implanted within the myometrium and is completely surrounded by myometrium with clear separation from both the uterine cavity and tubes. IMEP possesses not only diagnostic but also therapeutic challenge. The majority of reported cases were managed by hysterectomy. Early management of unruptured IMEP using methotrexate may help to preserve fertility. We, for the first time, report a case of ruptured IMEP managed successfully using suction and curettage followed by Bakri balloon tamponade and avoiding hysterectomy. Post-procedure, the patient received two doses of intramuscular methotrexate 50 mg/m2 due to plateauing serial beta human chorionic gonadotropin (β-hCG) levels and subsequently achieved undetectable level 10 weeks post-methotrexate. She also had complete resolution of the ectopic intramyometrial mass.
  4. Fulltext Use of the Arabin pessary in women at high risk for preterm birth: long-term experience at a single tertiary center in Malaysia
    Rahman RA, Atan IK, Ali A, Kalok AM, Ismail NAM, Mahdy ZA, et al.
    BMC Pregnancy Childbirth, 2021 May 10;21(1):368.
    PMID: 33971828 DOI: 10.1186/s12884-021-03838-x
    BACKGROUND: Spontaneous preterm birth is a global issue that contributed to perinatal morbidities and mortalities worldwide. The study aimed to describe the experience at UKM Medical Center in managing women at high risk for spontaneous preterm birth using the Arabin pessary.

    METHODS: This is a retrospective observational study involving 58 pregnancies from 1st January 2013 to 31st December 2019. Inclusion criteria were previous mid-trimester miscarriage and/or preterm birth, previous cervical surgery or short cervical length on routine sonogram. The demographic data, characteristics of each pregnancy and details of outcomes and management were described.

    RESULTS: The majority of women were Malay with mean age and body mass index of 32.9 ± 4.2 years and 27.1 ± 6.3 kg/m2 respectively. The most frequent indications for Arabin pessary insertion were previous mid-trimester miscarriage (46.4%) and early preterm birth (17.2%). A total of 73.4% of these women had the pessary inserted electively at a mean cervical length of 31.6 ± 9.1 mm at median gestation of 15.0 weeks. They were managed as outpatient (56.9%), inpatient (24.1%) or mixed (19.0%) with combination of progestogen (81.0%) and 53.4% received antenatal corticosteroids. Spontaneous preterm birth at or more than 34 weeks gestation occurred in 74.1% with birthweight at or more than 2000 g (82.4%). Despite cervical funneling in 12 women (20.7%), 66.7% delivered at or later than 34 weeks gestation and 2 (16.7%) resulted in miscarriage.

    CONCLUSIONS: Insertion of the Arabin pessary is beneficial to prevent spontaneous preterm birth in pregnant women who are at high risk. In particular, early insertion and close monitoring allows the best possible outcomes.

    TRIAL REGISTRATION: This study was retrospectively registered with ClinicalTrials.gov ( NCT04638023 ) on 20/11/2020.

  5. Transforming growth factor-alpha and nonsyndromic cleft lip with or without palate or cleft palate only in Kelantan, Malaysia
    Rahman RA, Ahmad A, Rahman ZA, Mokhtar KI, Lah NA, Zilfalil BA, et al.
    Cleft Palate Craniofac J, 2008 Nov;45(6):583-6.
    PMID: 18956930 DOI: 10.1597/07-020.1
    To determine the frequency of the transforming growth factor-alpha (TGFalpha) Taq1 polymorphism in nonsyndromic cleft lip with or without cleft palate (CL+/-P) and cleft palate only (CP) in Kelantan, Malaysia.
  6. Thermal Behavior of Selected Starches in Presence of Other Food Ingredients Studied by Differential Scanning Calorimetery (DSC)-Review
    Elgadir MA, Bakar J, Zaidul ISM, Rahman RA, Abbas KA, Hashim DM, et al.
    Compr Rev Food Sci Food Saf, 2009 Jul;8(3):195-201.
    PMID: 33467796 DOI: 10.1111/j.1541-4337.2009.00078.x
      This review article highlights the thermal behaviors of selected starches that were studied using differential scanning calorimetery (DSC) with data shown in various research publications. The starches of sago, potato, sweet potato, cassava, yam, and corn are included in this overview. Our examinations indicate that thermal properties are highly affected by the type of starch, its amylose/amylopectin content, and the presence of other food ingredients such as sugar, sodium chloride, water, milk, hydrocolloids, and meat. When the heating temperatures of the starches were increased, the DSC measurements also showed an increase in the temperatures of the gelatinization (onset [To ], peak [Tp ], and conclusion [Tc ]). This may be attributed to the differences in the degree of crystallinity of the starch, which provides structural stability and makes the granule more resistant to gelatinization.
  7. Fulltext The antibacterial properties of Malaysian tualang honey against wound and enteric microorganisms in comparison to manuka honey
    Tan HT, Rahman RA, Gan SH, Halim AS, Hassan SA, Sulaiman SA, et al.
    BMC Complement Altern Med, 2009;9:34.
    PMID: 19754926 DOI: 10.1186/1472-6882-9-34
    Antibiotic resistance of bacteria is on the rise, thus the discovery of alternative therapeutic agents is urgently needed. Honey possesses therapeutic potential, including wound healing properties and antimicrobial activity. Although the antimicrobial activity of honey has been effectively established against an extensive spectrum of microorganisms, it differs depending on the type of honey. To date, no extensive studies of the antibacterial properties of tualang (Koompassia excelsa) honey on wound and enteric microorganisms have been conducted. The objectives of this study were to conduct such studies and to compare the antibacterial activity of tualang honey with that of manuka honey.
  8. Fulltext The Short-Term Effect of Active Skeletonized Sutural Distractor Appliance on Temporomandibular Joint Morphology of Class III Malocclusion Subjects
    Huqh MZU, Hassan R, Rahman RA, Yusof A, Narmada IB, Ahmad WMAW
    Eur J Dent, 2021 Jul;15(3):523-532.
    PMID: 33622009 DOI: 10.1055/s-0040-1722483
    OBJECTIVES:  The purpose of this study was to evaluate the short-term effect of active skeletonized sutural distractor (ASSD) appliance on temporomandibular joint morphology of class III malocclusion subjects.

    MATERIALS AND METHODS:  This was a prospective interventional study. Cone-beam computerized tomography (CBCT) images of 22 patients were taken before and after treatment by using Planmeca Promax 3D CBCT machine version 2.9.2 (Planmeca OY Helsinki, Finland). The condylar width, height, length, roof of glenoid fossa thickness, and all joint spaces were measured. The condylar position was determined based on Pullinger and Hollander formula. The condylar shape was determined as per Kinzinger et al. The condylar volume was calculated by using Mimics software (Materialize, Belgium).

    STATISTICAL ANALYSIS:  Data analysis was performed by using SPSS software version 24. Wilcoxon paired signed-rank test was used to compare the difference in temporomandibular joint morphology and condylar volume between pre- and post-treatment measurements. Chi-square test was used to compare the condylar position and shape.

    RESULTS:  The superior (p = 0.000 on the right side, p = 0.005 on the left side) and posterior joint spaces (p = 0.000 on both sides) were decreased after the treatment, respectively. The condyles were rotated upward and backward, thereby increasing the anterior joint spaces (p = 0.000 on both sides) after the treatment. The condylar volume increases after treatment, but no significant differences were observed (p = 0.903 on the right side, p = 0.062 on the left side).

    CONCLUSION:  The significant changes were observed in joint spaces. The condyles were more anteriorly placed before treatment. Condylar position and shape alter in response to ASSD treatment. The condylar volume did not show any significant change.

  9. Fulltext The Role of Zinc Chloride in Enhancing Mechanical, Thermal and Electrical Performance of Ethylene Vinyl Acetate/Carbonized Wood Fiber Conductive Composite
    Mohd Pisal MH, Osman AF, Jin TS, Rahman RA, Alrashdi AA, Masa A
    Polymers (Basel), 2021 Feb 17;13(4).
    PMID: 33671304 DOI: 10.3390/polym13040600
    Carbonized natural filler can offer the production of low cost composites with an eco-friendliness value. The evolving field of electronics encourages the exploration of more functions and potential for carbonized natural filler, such as by modifying its surface chemistry. In this work, we have performed surface modification on carbonized wood fiber (CWF) prior to it being used as filler in the ethylene vinyl acetate (EVA) composite system. Zinc chloride (ZnCl2) with various contents (2 to 8 wt%) was used to surface modify the CWF and the effects of ZnCl2 composition on the surface morphology and chemistry of the CWF filler were investigated. Furthermore, the absorptive, mechanical, thermal, and electrical properties of the EVA composites containing CWF-ZnCl2 were also analyzed. SEM images indicated changes in the morphology of the CWF while FTIR analysis proved the presence of ZnCl2 functional groups in the CWF. EVA composites incorporating the CWF-ZnCl2 showed superior mechanical, thermal and electrical properties compared to the ones containing the CWF. The optimum content of ZnCl2 was found to be 6 wt%. Surface modification raised the electrical conductivity of the EVA/CWF composite through the development of conductive deposits in the porous structure of the CWF as a channel for ionic and electronic transfer between the CWF and EVA matrix.
  10. Fulltext The Mentakab hypertension study project. Part V--Drug compliance in hypertensive patients
    Lim TO, Ngah BA, Rahman RA, Suppiah A, Ismail F, Chako P, et al.
    Singapore Med J, 1992 Feb;33(1):63-6.
    PMID: 1598610
    Poor compliance with drug treatment is a barrier to effective management of hypertension. Drug compliance behaviour of 168 patients were studied, their drug compliance was measured by the pill-counting method. The prevalence of non-compliance with medication was 26%. Thirteen variables were examined for their association with compliance; these were age, sex, duration of hypertension since diagnosis, adequacy of blood pressure control, complexity of drug regimen and side-effect of drug, history of previous admission for hypertension related reason, patient's knowledge of hypertensive complications, patient's belief that drug was 'panas' or 'san', previous use of traditional treatment for hypertension, patient's fatalistic attitude, their social support and satisfaction with the health services. None of these variables were significantly related to compliance (p greater than 0.05) except adequacy of blood pressure control. The performance of patient self-report was compared with pill-count as a measure of drug compliance; it was poorly predictive of non-compliance (sensitivity = 71%, specificity = 50%). An inverse relationship was found between non-compliance with medication and patient subsequent drop-out rate. Patients who were compliant were more likely to remain on treatment and vice versa. As a measure of drug compliance, detection of drop-out compared well with pill-count (sensitivity 97%, specificity 66%, positive predictive value 89%, negative predictive value 88%).
    Study site: outpatient clinic, Hospital Mentakab, Pahang, Malaysia
  11. Fulltext Supercritical carbon dioxide extraction of seed oil from winter melon (Benincasa hispida) and its antioxidant activity and fatty acid composition
    Bimakr M, Rahman RA, Taip FS, Adzahan NM, Sarker MZ, Ganjloo A
    Molecules, 2013 Jan 15;18(1):997-1014.
    PMID: 23322066 DOI: 10.3390/molecules18010997
    In the present study, supercritical carbon dioxide (SC-CO(2)) extraction of seed oil from winter melon (Benincasa hispida) was investigated. The effects of process variables namely pressure (150-300 bar), temperature (40-50 °C) and dynamic extraction time (60-120 min) on crude extraction yield (CEY) were studied through response surface methodology (RSM). The SC-CO(2) extraction process was modified using ethanol (99.9%) as co-solvent. Perturbation plot revealed the significant effect of all process variables on the CEY. A central composite design (CCD) was used to optimize the process conditions to achieve maximum CEY. The optimum conditions were 244 bar pressure, 46 °C temperature and 97 min dynamic extraction time. Under these optimal conditions, the CEY was predicted to be 176.30 mg-extract/g-dried sample. The validation experiment results agreed with the predicted value. The antioxidant activity and fatty acid composition of crude oil obtained under optimized conditions were determined and compared with published results using Soxhlet extraction (SE) and ultrasound assisted extraction (UAE). It was found that the antioxidant activity of the extract obtained by SC-CO(2) extraction was strongly higher than those obtained by SE and UAE. Identification of fatty acid composition using gas chromatography (GC) showed that all the extracts were rich in unsaturated fatty acids with the most being linoleic acid. In contrast, the amount of saturated fatty acids extracted by SE was higher than that extracted under optimized SC-CO(2) extraction conditions.
  12. Studying the effects of nucleating agents on texture modification of puffed corn-fish snack
    Shahmohammadi HR, Bakar J, Rahman RA, Adzhan NM
    J Food Sci, 2014 Feb;79(2):E178-83.
    PMID: 24410375 DOI: 10.1111/1750-3841.12324
    To improve textural attributes of puffed corn-fish snack, the effects of 1%, 1.5%, and 2% of calcium carbonate, magnesium silicate (talc), sodium bicarbonate as well as 5% and 10% of wheat bran (as the nucleating materials) on textural attributes were studied. Sensory evaluation, bulk density, expansion ratio, maximum force, and count peaks were measured using the Kramer test. The results showed that all of the additives except bran significantly enhanced the texture. Among them, talc at 0.5% was the best to enhance the density and expansion ratio. Effects of using 0.5% talc on puffed corn-fish snack microstructure were studied using scanning electron microscopy. The average cell diameter of 109 ± 48 μm and cell numbers per square centimeter of 67.4 for talc-treated products were obtained, while for nontalc-treated extrudates, average cell diameter of 798 ± 361 μm and cell numbers per square centimeter of 13.9 were found. Incorporation of 0.5% w/w of magnesium silicate reduced (7-fold) the average cell diameter while increased (4-fold) the cell number.
  13. Simultaneous removal of AOX and COD from real recycled paper wastewater using GAC-SBBR
    Osman WH, Abdullah SR, Mohamad AB, Kadhum AA, Rahman RA
    J Environ Manage, 2013 May 30;121:80-6.
    PMID: 23524399 DOI: 10.1016/j.jenvman.2013.02.005
    A lab-scale granular activated carbon sequencing batch biofilm reactor (GAC-SBBR), a combined adsorption and biological process, was developed to treat real wastewater from a recycled paper mill. In this study, one-consortia of mixed culture (4000-5000 mg/L) originating from recycled paper mill activated sludge from Kajang, Malaysia was acclimatized. The GAC-SBBR was fed with real wastewater taken from the same recycled paper mill, which had a high concentration of chemical oxygen demand (COD) and adsorbable organic halides (AOX). The operational duration of the GAC-SBBR was adjusted from 48 h to 24, 12 and finally 8 h to evaluate the effect of the hydraulic retention time (HRT) on the simultaneous removal of COD and AOX. The COD and AOX removals were in the range of 53-92% and 26-99%, respectively. From this study, it was observed that the longest HRT (48 h) yielded a high removal of COD and AOX, at 92% and 99%, respectively.
  14. Simplified feeding strategies for the fed-batch cultivation of Kluyveromyces lactis GG799 for enhanced recombinant xylanase production
    Fuzi SF, Razali F, Jahim JM, Rahman RA, Illias RM
    Bioprocess Biosyst Eng, 2014 Sep;37(9):1887-98.
    PMID: 24633311 DOI: 10.1007/s00449-014-1163-z
    A xylanase gene (xyn2) from Trichoderma reesei ATCC 58350 was previously cloned and expressed in Kluyveromyces lactis GG799. The production of the recombinant xylanase was conducted in a developed medium with an optimised batch and with fed-batches that were processed with glucose. The glucose served as a carbon source for cell growth and as an inducer for xylanase production. In a 1-L batch system, a glucose concentration of 20 g L(-1) and 80 % dissolved oxygen were found to provide the best conditions for the tested ranges. A xylanase activity of 75.53 U mL(-1) was obtained. However, in the batch mode, glucose depletions reduced the synthesis of recombinant xylanase by K. lactis GG799. To maximise the production of xylanase, further optimisation was performed using exponential feeding. We investigated the effects of various nitrogen sources combined with the carbon to nitrogen (C/N) molar ratio on the production of xylanase. Of the various nitrogen sources, yeast extract was found to be the most useful for recombinant xylanase production. The highest xylanase production (110.13 U mL(-1)) was measured at a C/N ratio of 50.08. These conditions led to a 45.8 % increase in xylanase activity compared with the batch cultures. Interestingly, the further addition of 500 g L(-1) glucose led to a 6.2-fold increase (465.07 U mL(-1)) in recombinant xylanase activity. These findings, together with those of the exponential feeding strategy, indicate that the composition of the C/N molar ratio has a substantial impact on recombinant protein production in K. lactis.
  15. Silver/poly (lactic acid) nanocomposites: preparation, characterization, and antibacterial activity
    Shameli K, Ahmad MB, Yunus WM, Ibrahim NA, Rahman RA, Jokar M, et al.
    Int J Nanomedicine, 2010 Sep 07;5:573-9.
    PMID: 20856832
    In this study, antibacterial characteristic of silver/poly (lactic acid) nanocomposite (Ag/PLA-NC) films was investigated, while silver nanoparticles (Ag-NPs) were synthesized into biodegradable PLA via chemical reduction method in diphase solvent. Silver nitrate and sodium borohydride were respectively used as a silver precursor and reducing agent in the PLA, which acted as a polymeric matrix and stabilizer. Meanwhile, the properties of Ag/PLA-NCs were studied as a function of the Ag-NP weight percentages (8, 16, and 32 wt% respectively), in relation to the use of PLA. The morphology of the Ag/PLA-NC films and the distribution of the Ag-NPs were also characterized. The silver ions released from the Ag/PLA-NC films and their antibacterial activities were scrutinized. The antibacterial activities of the Ag/PLA-NC films were examined against Gram-negative bacteria (Escherichia coli and Vibrio parahaemolyticus) and Gram-positive bacteria (Staphylococcus aureus) by diffusion method using Muller-Hinton agar. The results indicated that Ag/PLA-NC films possessed a strong antibacterial activity with the increase in the percentage of Ag-NPs in the PLA. Thus, Ag/PLA-NC films can be used as an antibacterial scaffold for tissue engineering and medical application.
  16. Severity of Malaria cases reported in urban and rural hospitals in Malaysia
    Nimir AR, Isa NH, Eugene CB, Ghauth IM, Salleh FM, Rahman RA
    Southeast Asian J. Trop. Med. Public Health, 2006 Sep;37(5):831-7.
    PMID: 17333723
    The age distribution, types of infection and clinical patterns of malaria were compared in patients admitted to an urban and a rural hospital. Analysis of the cases seen in urban setting characteristically indicated a relatively low transmission rate of the disease, whereas the mean inoculation rate in patients from the rural hospital was found to be at least twenty folds higher. Plasmodium vivax was the predominant causative species in the urban hospital (p = 0.01), infecting mostly adult (p = 0.001) males (p = 0.01). The geometric mean parasite count at 3432/microl among the urban patients was significantly higher than that in the rural patients at 1422/microl (p = 0.04). Coma and death were more common among the cases seen in the urban hospital (p = 0.003), while severe anemia was the significant complication in the rural setting. Overall, the provisional diagnosis of malaria was relatively low in the urban hospital (p = 0.02). The results from this study highlighted the need to define the extent of malaria in urban areas. This report attempts to identify the non-climatic determinants of the infection and, furthermore, to provide a more informed basis to describe the burden of the disease.
  17. Second twin outcome at birth: retrospective analysis in a single tertiary centre in Malaysia
    Rahman RA, Mohammed Nawi A, Ishak S, Balaraman K, Abu MA, Abd Azman SH, et al.
    J Perinat Med, 2024 Mar 22.
    PMID: 38511669 DOI: 10.1515/jpm-2023-0449
    OBJECTIVES: To investigate factors associated with outcome of second twin during labour.

    METHODS: The study was a retrospective cohort study in a single tertiary centre in Malaysia from 2014 until 2018 involving all twin pregnancies delivered at or more than 24 weeks of gestation.

    RESULTS: Total of 409 twin pregnancies were included. Dichorionic twin comprises of 54.5 % (n=223) and 45.5 % (n=186) are monochorionic. Women with dichorionic pregnancies are significantly older (p<0.001), have more pre-existing medical disorders (p=0.011) and fetal structural anomalies (p=0.009). Monochorionic pregnancies are significantly more amongst Malay (p=0.01) and conceived spontaneously (p<0.001). There are significantly more fetuses both in cephalic presentation (p=0.026), birthweight discrepancy more than 20 % (p=0.038) and shorter mean inter-twin delivery duration (p=0.048) in monochorionic pregnancies. Second twin delivered with Apgar score <7 is significantly more in dichorionic pregnancies (p=0.006). The second twin is associated with lower birthweight, small for gestational age and arterial cord pH<7.25. Within the group of women who delivered both fetuses vaginally, there was significantly more second twins with intertwin delivery duration less than 30 min who were delivered vaginally without instrumentation (p=0.018). There was significantly more second twin with intertwin delivery duration of 30 min and more with arterial cord pH<7.25 (p=0.045). Those who delivered spontaneously had inter-twin delivery duration within 15-29 min. The outcome of second twin is not influenced by type of twin, gestational age at delivery, inter-twin delivery duration, mode of delivery and presentation at birth.

    CONCLUSIONS: The neonatal outcome for the second twin at birth is not influenced by type of twin, gestational age at delivery, inter-twin delivery duration, mode of delivery and presentation at birth in a cohort managed with non-active management of the second twin in Malaysia.

  18. Robust cross-linked cyclodextrin glucanotransferase from Bacillus lehensis G1 aggregates using an improved cross-linker and a new co-aggregant for the production of cyclodextrins
    Jailani N, Jaafar NR, Rahman RA, Illias RM
    Enzyme Microb Technol, 2023 Sep;169:110283.
    PMID: 37433237 DOI: 10.1016/j.enzmictec.2023.110283
    One of the potentials of carrier-free cross-linked enzyme aggregates (CLEA) immobilization is the ability to be separated and reuse. Yet, it might be impeded by the poor mechanical stability resulting low recyclability. CLEA of CGTase from Bacillus lehensis G1 (CGTase G1-CLEA) using chitosan (CS) as a cross-linker demonstrated high activity recovery however, displayed poor reusability. Therefore, the relationship between mechanical strength and reusability is studied by enhancing the CS mechanical properties and applying a new co-aggregation approach. Herein, CS was chemically cross-linked with glutaraldehyde (GA) and GA was introduced as a co-aggregant (coGA). CGTase G1-CLEA developed using an improved synthesized chitosan-glutaraldehyde (CSGA) cross-linker and a new coGA technique showed to increase its mechanical stability which retained 63.4% and 52.2%, respectively compared to using CS that remained 33.1% of their initial activity after stirred at 500 rpm. The addition of GA impacted the morphology and interaction consequently stabilizing the CLEAs durability in production of cyclodextrins. As a result, the reusability of CGTase G1-CLEA with CSGA and coGA increased by 56.6% and 42.8%, respectively compared to previous CLEA after 5 cycles for 2 h of reaction. This verifies that the mechanical strength of immobilized enzyme influences the improvement of its operational stability.
  19. Fulltext Response Surface Methodology for the Optimization of Preparation of Biocomposites Based on Poly(lactic acid) and Durian Peel Cellulose
    Penjumras P, Rahman RA, Talib RA, Abdan K
    ScientificWorldJournal, 2015;2015:293609.
    PMID: 26167523 DOI: 10.1155/2015/293609
    Response surface methodology was used to optimize preparation of biocomposites based on poly(lactic acid) and durian peel cellulose. The effects of cellulose loading, mixing temperature, and mixing time on tensile strength and impact strength were investigated. A central composite design was employed to determine the optimum preparation condition of the biocomposites to obtain the highest tensile strength and impact strength. A second-order polynomial model was developed for predicting the tensile strength and impact strength based on the composite design. It was found that composites were best fit by a quadratic regression model with high coefficient of determination (R (2)) value. The selected optimum condition was 35 wt.% cellulose loading at 165°C and 15 min of mixing, leading to a desirability of 94.6%. Under the optimum condition, the tensile strength and impact strength of the biocomposites were 46.207 MPa and 2.931 kJ/m(2), respectively.
  20. Quality of margarine: fats selection and processing parameters
    Miskandar MS, Man YC, Yusoff MS, Rahman RA
    Asia Pac J Clin Nutr, 2005;14(4):387-95.
    PMID: 16326646
    Optimum processing conditions on palm oil-based formulations are required to produce the desired quality margarine. As oils and fats contribute to the overall property of the margarine, this paper will review the importance of beta' tending oils and fats in margarine formulation, effects of the processing parameters -- emulsion temperature, flow-rate, product temperature and pin-worker speed -- on palm oil margarines produced and their subsequent behaviour in storage. Palm oil, which contributes the beta' crystal polymorph and the best alternative to hydrogenated liquid fats, and the processing conditions can affect the margarine consistency by influencing the solid fat content (SFC) and the types of crystal polymorph formed during production as well as in storage. Palm oil, or hydrogenated palm oil and olein, in mixture with oils of beta tending, can veer the product to the beta' crystal form. However, merely having beta' crystal tending oils is not sufficient as the processing conditions are also important. The emulsion temperature had no significant effect on the consistency and polymorphic changes of the product during storage, even though differences were observed during processing. The consistency of margarine during storage was high at low emulsion flow-rates and low at high flow rates. The temperature of the scraped-surface tube-cooler is the most important parameter in margarine processing. High temperature will produce a hardened product with formation of beta-crystals during storage. The speed of the pin-worker is responsible for inducing crystallization but, at the same time, destroys the crystal agglomerates, resulting in melting.
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