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Search Results: 1 - 10 of 13852 matches for " Siew-Ling Hii "
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Equilibrium and Kinetic Studies for Basic Yellow 11 Removal by Sargassum binderi
Pei-Ling Tan,Ching-Lee Wong,Siew-Teng Ong,Siew-Ling Hii
Journal of Applied Sciences , 2009,
Abstract: Dyes have been widely used in many industries such as textile, paint and also ink industry. Discharge of dyes from these industries need to undergo treatment prior of disposal to avoid ecosystem to be devastated. Upon this, Sargassum binderi, a species of brown seaweed was used as a low cost biosorbent to remove a basic dye, Basic Yellow 11 (BY11). Various parameters such as pH, initial concentration and sorbent dosage were conducted using batch sorption process. In this study, S. binderi exhibited good performance (almost 100% of BY11 removal) with 1 g of sorbent dosage in 100 mg L-1 of dye solution. pH of the solution, however, does not seem to have high influence on removal of BY11. Langmuir, Freundlich and Temkin isotherm models were used to study sorption behaviors of S. binderi at equilibrium stage. From the analysis, the sorption of BY11 onto the S. binderi was found obeyed Freundlich model with coefficient correlation (R2) value of 0.9959 which indicates heterogeneous layers of sorption. The Freundlich constant, KF and n values obtained were 32.46 mg g-1 (L mg-1)1/n and 1.968, respectively. Value of Freundlich component, n, was more than 1 indicates favourable adsorption process of this system. The kinetic sorption of BY11 using S. binderi were analyzed by using pseudo-first-order, pseudo-second-order and intraparticular diffusion model. The sorption process followed pseudo-second-order kinetic which involved chemisorption. Calculated qe values from pseudo-second-order kinetic model were found fitted well with the experimental qe values. Each R2 values from linear regression line of pseudo-second-order kinetic model were more than 0.99. In this study, S. binderi was proven to have high sorption efficiency towards BY11 and thus, it can be categorized as one of the promising biosorbent to be applied in treating the effluent discharge from industries.
Production of Cyclodextrin Glycosyltransferase (CGTase) by Bacillus lehensis S8 using Sago Starch as Carbon Source
Pui-Woon Yap,Arbakariya B. Ariff,Kwan-Kit Woo,Siew-Ling Hii
Journal of Biological Sciences , 2010,
Abstract: Production of cyclodextrin glycosyltransferase (CGTase) is influenced by the reaction of the CGTase-producing strain towards various types of substrates. Variations in environmental factors such as concentrations of carbon and nitrogen sources possess significant effects on CGTase production. The present study was conducted with the prime purpose to optimise the cultivation medium in enhancing the CGTase production by a locally isolated alkalophilic Bacillus sp. The CGTase fermentation processes were performed in 250 mL Erlenmeyer flasks containing 200 mL of production medium with continuous shaking at 200 rpm and 37°C. Optimisation process was conducted by using change-a-factor-at-a-time method. From the study, an indigenous Malaysian carbon source, i.e., sago starch was found capable in improving the CGTase production with the CGTase yield of 18452 U g-1 at 0.1% w/v of starch. In addition to that, by using yeast extract as the sole nitrogen source in the medium, the CGTase excretion by the isolate is greatly enhanced as compared to the basal medium which employed two types of nitrogenous compounds. The optimised growth medium that has been successfully developed for high level of CGTase production by using the locally isolated Bacillus lehensis in 250 mL Erlenmeyer flask is comprised of (% w/v): 0.1% sago starch, 1% yeast extract, 1% sodium carbonate, 0.009% magnesium sulphate and 0.1% di-potassium hydrogen phosphate.
Pullulanase: Role in Starch Hydrolysis and Potential Industrial Applications
Siew Ling Hii,Joo Shun Tan,Tau Chuan Ling,Arbakariya Bin Ariff
Enzyme Research , 2012, DOI: 10.1155/2012/921362
Abstract: The use of pullulanase (EC has recently been the subject of increased applications in starch-based industries especially those aimed for glucose production. Pullulanase, an important debranching enzyme, has been widely utilised to hydrolyse the α-1,6 glucosidic linkages in starch, amylopectin, pullulan, and related oligosaccharides, which enables a complete and efficient conversion of the branched polysaccharides into small fermentable sugars during saccharification process. The industrial manufacturing of glucose involves two successive enzymatic steps: liquefaction, carried out after gelatinisation by the action of α-amylase; saccharification, which results in further transformation of maltodextrins into glucose. During saccharification process, pullulanase has been used to increase the final glucose concentration with reduced amount of glucoamylase. Therefore, the reversion reaction that involves resynthesis of saccharides from glucose molecules is prevented. To date, five groups of pullulanase enzymes have been reported, that is, (i) pullulanase type I, (ii) amylopullulanase, (iii) neopullulanase, (iv) isopullulanase, and (v) pullulan hydrolase type III. The current paper extensively reviews each category of pullulanase, properties of pullulanase, merits of applying pullulanase during starch bioprocessing, current genetic engineering works related to pullulanase genes, and possible industrial applications of pullulanase. 1. Introduction Starch is a major industrial raw material and is chemically and/or enzymatically processed into variety of products for subsequent use in various industries, ranging from food (especially high-fructose and glucose syrups) to washing detergent industries [1–3]. Starch is, after cellulose, one of the most abundant heterogeneous polysaccharide produced by plants in the form of water insoluble granules. It is a polymeric carbohydrate, composed of C, H, and O atoms in the ratio of 6?:?10?:?5, (C6H10O5)??. Molecules of starch are made of hundreds or thousands of glucose, corresponding to values of ?? that range from 50 to several thousands. Glucose units are linked to one another through C1 oxygen as glucosidic bond. Glucosidic bonds are stable under alkaline conditions while treatment of starch with acids or certain enzymes breaks the polymer into its constituent glucose molecules. The end unit of the polymeric chain has a latent aldehyde group and is known as the reducing end group. Most starches are mixture of two polymers with high molecular weight: (i) a linear chain molecule—amylose, and (ii) a branch
A High Molecular-Mass Anoxybacillus sp. SK3-4 Amylopullulanase: Characterization and Its Relationship in Carbohydrate Utilization
Ummirul Mukminin Kahar,Kok-Gan Chan,Madihah Md. Salleh,Siew Mee Hii,Kian Mau Goh
International Journal of Molecular Sciences , 2013, DOI: 10.3390/ijms140611302
Abstract: An amylopullulanase of the thermophilic Anoxybacillus sp. SK3-4 (ApuASK) was purified to homogeneity and characterized. Though amylopullulanases larger than 200 kDa are rare, the molecular mass of purified ApuASK appears to be approximately 225 kDa, on both SDS-PAGE analyses and native-PAGE analyses. ApuASK was stable between pH 6.0 and pH 8.0 and exhibited optimal activity at pH 7.5. The optimal temperature for ApuASK enzyme activity was 60 °C, and it retained 54% of its total activity for 240 min at 65 °C. ApuASK reacts with pullulan, starch, glycogen, and dextrin, yielding glucose, maltose, and maltotriose. Interestingly, most of the previously described amylopullulanases are unable to produce glucose and maltose from these substrates. Thus, ApuASK is a novel, high molecular-mass amylopullulanase able to produce glucose, maltose, and maltotriose from pullulan and starch. Based on whole genome sequencing data, ApuASK appeared to be the largest protein present in Anoxybacillus sp. SK3-4. The α-amylase catalytic domain present in all of the amylase superfamily members is present in ApuASK, located between the cyclodextrin (CD)-pullulan-degrading N-terminus and the α-amylase catalytic C-terminus (amyC) domains. In addition, the existence of a S-layer homology (SLH) domain indicates that ApuASK might function as a cell-anchoring enzyme and be important for carbohydrate utilization in a streaming hot spring.
Short Term Effects of Weather on Hand, Foot and Mouth Disease
Yien Ling Hii,Joacim Rockl?v,Nawi Ng
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016796
Abstract: Hand, foot, and mouth disease (HFMD) outbreaks leading to clinical and fatal complications have increased since late 1990s; especially in the Asia Pacific Region. Outbreaks of HFMD peaks in the warmer season of the year, but the underlying factors for this annual pattern and the reasons to the recent upsurge trend have not yet been established. This study analyzed the effect of short-term changes in weather on the incidence of HFMD in Singapore.
On the Design Preferences for Ebooks
Chong Pei,Lim Yan,Ling Siew
IETE Technical Review , 2009,
Abstract: While many academic libraries are increasingly providing e-book services, a barrier to the adoption of e-books, however, is their unsatisfactory design. This paper reports on a study that investigates the students′ preferences for the e-book designs, in an attempt to review what appeals to them in an ideal e-book. Comparison was made between three e-books in portable document format, all of which were non-fiction, but differed in contents and their styles of presentation. Based on the preliminary findings, some general guidelines were suggested for the improved design of e-books.
Genotoxic Potential of Shrimp Pastes (Belacan) Extracts Using Umu Test  [PDF]
Ahmad Rohi Ghazali, Yvonne Sipain, Nor Fadilah Rajab, Siew Ee Ling, Norain Ramli, Rozaini Abdullah, Zaliha Harun, Firdaus Kamarulzaman
Food and Nutrition Sciences (FNS) , 2012, DOI: 10.4236/fns.2012.34073
Abstract: This study was conducted to observe the genotoxic effects of aqueous, methanol, hexane and dichloromethane extracts of “belacan” (shrimp paste) taken from three local districts in Melaka, Malaysia (Kelemak, Batang Tiga & Pantai Puteri). The umu test which was used as the screening test was conducted with and without the presence of metabolic activation system. Without the presence of metabolic activation system, aqueous extracts from Kelemak showed mutagenicity activity at 5 mg/ml with IR (Induction Rate) = 1.52 ± 0.57 and the methanol extracts showed mutagenic activities at 0.625 mg/ml and 5 mg/ml, which the IR was the highest at 5 mg/ml (2.08 ± 0.09). On the other hand, samples from Batang Tiga, Melaka showed mutagenic effects at all five concentrations for the dichloromethane extract, with IR = 2.09 ± 0.64 as the highest value at 1.25 mg/ml. Methanol extracts also showed positive results at 1.25 mg/ml and 2.5 mg/ml with IR = 1.70 ± 0.33 and IR = 2.12 ± 0.51 respectively, and aqueous extract at 0.625 mg/ml with IR = 1.54 ± 0.48 and 5 mg/ml with IR = 1.74 ± 0.50. There was a significant difference of the mean values of IR between the four different types of “belacan” extracts from Batang Tiga (p < 0.05). All four “belacan” extracts from Pantai Puteri, Melaka did not show any mutagenic effect. With the presence of metabolic activation system, there was no mutagenic effect observed in all four extracts from the three districts. Further study to analyze the contents in the food samples should be done in the future to determine the possible contents in the food samples that might be responsible for the mutagenic activities.
Optimal Lead Time for Dengue Forecast
Yien Ling Hii ,Joacim Rockl?v,Stig Wall,Lee Ching Ng,Choon Siang Tang,Nawi Ng
PLOS Neglected Tropical Diseases , 2012, DOI: 10.1371/journal.pntd.0001848
Abstract: Background A dengue early warning system aims to prevent a dengue outbreak by providing an accurate prediction of a rise in dengue cases and sufficient time to allow timely decisions and preventive measures to be taken by local authorities. This study seeks to identify the optimal lead time for warning of dengue cases in Singapore given the duration required by a local authority to curb an outbreak. Methodology and Findings We developed a Poisson regression model to analyze relative risks of dengue cases as functions of weekly mean temperature and cumulative rainfall with lag times of 1–5 months using spline functions. We examined the duration of vector control and cluster management in dengue clusters > = 10 cases from 2000 to 2010 and used the information as an indicative window of the time required to mitigate an outbreak. Finally, we assessed the gap between forecast and successful control to determine the optimal timing for issuing an early warning in the study area. Our findings show that increasing weekly mean temperature and cumulative rainfall precede risks of increasing dengue cases by 4–20 and 8–20 weeks, respectively. These lag times provided a forecast window of 1–5 months based on the observed weather data. Based on previous vector control operations, the time needed to curb dengue outbreaks ranged from 1–3 months with a median duration of 2 months. Thus, a dengue early warning forecast given 3 months ahead of the onset of a probable epidemic would give local authorities sufficient time to mitigate an outbreak. Conclusions Optimal timing of a dengue forecast increases the functional value of an early warning system and enhances cost-effectiveness of vector control operations in response to forecasted risks. We emphasize the importance of considering the forecast-mitigation gaps in respective study areas when developing a dengue forecasting model.
Application of a high density adsorbent in expanded bed adsorption of lipase from Burkholderia pseudomallei
HS Yong, BT Tey, SL Hii, SMM Kamal, A Ariff, TC Ling
African Journal of Biotechnology , 2010,
Abstract: The application of STREAMLINE Direct HST adsorbent in expanded bed adsorption of lipase from Burkholderia pseudomallei was explored in this study. Scouting of optimum binding and elution condition was performed in batch binding mode. The addition of 0.2 M salt in acetate buffer (pH 5) during adsorption has increased the specificity and quantity of lipase binding onto the adsorbent. The addition of 0.4 M salt in phosphate buffer (pH 7) achieved the highest purification fold (2.5) in elution. The high density of the adsorbent allowed the EBA to be operated at linear velocity as high as 657 cm/h with feedstock containing 4.5% (w/v) wet biomass. The Richardson-Zaki correlation obtained for this EBA system at the presence of 4.5% (w/v) wet biomass is 5.14, a value closed to the laminar flow regime of 4.8, demonstrated that a stable bed is achieved under this operating condition. Meanwhile, a flow velocity of 343 cm/h with bed expansion of 3.2 gave highest dynamic binding capacity (4979.28 U/ml) and productivity (61.52 U/ml.min) for this EBA operation. It also demonstrated that biomass concentration up to 4.5% (w/v) wet weight showed slightly drop of sorption efficiency (0.82) compared to lower biomass concentration (0.94). Further increase of biomass concentration above 4.5% (w/v) wet weight has greatly decreased the equilibrium and dynamic capacity. Application of high density adsorbent tolerated to high density and biomass has reduced the processing time and increased the productivity.
Forecast of Dengue Incidence Using Temperature and Rainfall
Yien Ling Hii ,Huaiping Zhu,Nawi Ng,Lee Ching Ng,Joacim Rockl?v
PLOS Neglected Tropical Diseases , 2012, DOI: 10.1371/journal.pntd.0001908
Abstract: Introduction An accurate early warning system to predict impending epidemics enhances the effectiveness of preventive measures against dengue fever. The aim of this study was to develop and validate a forecasting model that could predict dengue cases and provide timely early warning in Singapore. Methodology and Principal Findings We developed a time series Poisson multivariate regression model using weekly mean temperature and cumulative rainfall over the period 2000–2010. Weather data were modeled using piecewise linear spline functions. We analyzed various lag times between dengue and weather variables to identify the optimal dengue forecasting period. Autoregression, seasonality and trend were considered in the model. We validated the model by forecasting dengue cases for week 1 of 2011 up to week 16 of 2012 using weather data alone. Model selection and validation were based on Akaike's Information Criterion, standardized Root Mean Square Error, and residuals diagnoses. A Receiver Operating Characteristics curve was used to analyze the sensitivity of the forecast of epidemics. The optimal period for dengue forecast was 16 weeks. Our model forecasted correctly with errors of 0.3 and 0.32 of the standard deviation of reported cases during the model training and validation periods, respectively. It was sensitive enough to distinguish between outbreak and non-outbreak to a 96% (CI = 93–98%) in 2004–2010 and 98% (CI = 95%–100%) in 2011. The model predicted the outbreak in 2011 accurately with less than 3% possibility of false alarm. Significance We have developed a weather-based dengue forecasting model that allows warning 16 weeks in advance of dengue epidemics with high sensitivity and specificity. We demonstrate that models using temperature and rainfall could be simple, precise, and low cost tools for dengue forecasting which could be used to enhance decision making on the timing, scale of vector control operations, and utilization of limited resources.
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