Miradatul Najwa Mohd Rodhi

Nanoclay Supporting Materials for Enzymes Immobilization: Kinetics Investigation of Free and Immobilized System

In this paper, the kinetic parameters of free and encapsulated enzymes in the calcium alginate-clay beads were determined using Lineweaver-Burk plot. The Michaelis constant, Km of free alpha-amylase, glucoamylase and cellulase were 2.0831, 1.8326 and 7.8592 mg/mL, respectively, whereas for the encapsulated system, the Km values were 3.1604, 2.1708 and 9.2791 mg/mL, respectively. The results showed encapsulation enzymes gave higher Km value than the free enzymes. Comparatively the encapsulated alpha-amylase was 1.5 times higher and the glucoamylase and cellulase were 1.18 times higher. This suggests that the affinity of encapsulated enzymes for substrate was lower which might be due to the diffusional limitation of the substrate and enzymes. Amongst the three in both systems, glucoamylase was determined to have highest affinity followed by alpha-amylase and cellulase enzymes.

Preparation and Characterization of Sg. Sayong Clay Material for Biocatalyst Immobilization

This study was conducted to characterize Sg. Sayong clay so that it can be applied as a supporting material for the immobilization of biocatalyst in the bioconversion of wastewater into biofuel. The clay sample was physically and chemically characterized using Nitrogen Adsorption, X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FTIR), Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Field Emission Scanning Electron Microscopy (FESEM). The results obtained showed that the clay composed of SiO2 (57.4%), followed by Al2O3 (32.5%), K2O (4.9%), Fe2O3 (3.8%) and traces amount of Ca, Mg, Ma, and Ti. The results also showed the clay type was kaolinite with some presence of quartz, illite, montmorillonite and microcline. The clay was also successfully coated onto the wire-mesh and immobilized with biocatalyst for further bioconversion study.

Heat effects from far-infrared source towards antioxidant activity in Aquilaria subintegra leaves

Aquilaria tree is known for its ability of producing high quality resin called agarwood or gaharu oil. The leaves of this tree were under utilized and it is also claimed to be useful for treating a certain diseases. This study was aimed to identify the present of antioxidant activities in Aquilariasubintegra leaves. In the meantime, the effect of drying temperature from far-infrared (FIR) sources on antioxidant activity of the plant leaves was studied. Leaves were dried at different temperatures (40 °C, 50 °C, 60 °C) by using a (FIR) dryer. DPPH method was used to identify the scavenging activity (IC50) of the methanolic leaves extracts. The result showed that methanol extract of the sample dried at 50 °C exhibited the highest antioxidant activity (IC50 of 619.89μg/ml). In the range of temperature studied, 50 °C is proposed to be an appropriate drying temperature when using FIR as the source of heating element. In conclusion, FIR helps in lowering the drying temperature of Aquilariasubintegra leaves that retain significant amount of antioxidant activities which could be beneficial for treating certain diseases as claimed by others.

The Effect of Natural Rubber and Plasticizer Addition on the Mechanical Properties of Tacca leontopetaloides Starch Based Polymer

The effect of natural rubber and glycerol addition on the mechanical performance of Tacca leontopetaloides biopolymer was investigated in this paper. The samples were formulated by varying blend ratios of latex natural rubber to glycerol; 40/30 (GM1), 50/5.85 (GM2), 60/30 (GM3), 40/10 (GM4) and 50/20 (GM5). The samples (GMs) were compounded by using two roll mill machine followed by vulcanization process with the presence of stearic acid and sulphur that act as curing agent. The sheet formed was cut into desired sizes, based on the analysis conducted. The mechanical performance of GMs was investigated by conducting tensile test, morphological structural analysis and water absorption test. The mechanical properties of GM2 showed a high tensile strength with low Young’s modulus compared to other GMs, thus indicating that GM2 was the superior combination of natural rubber to glycerol blend ratio. This, therefore, may be applied for the development of biopolymer with the properties of thermoplastic elastomer.

Chemical and Thermal Characterization of Dilute Sulfuric Acid Hydrolysis of Coconut Dregs

Coconut dregs that are commonly used for animal feed have the potential for glucose production due to high carbohydrate content. Nevertheless, no study found on understanding the properties of this biomass. Hence, the main purpose of this paper was to propose appropriate operational conditions for the dilute sulfuric acid hydrolysis of coconut dregs and to investigate the chemical and thermal properties of coconut dregs. The biomass was hydrolyzed with 1% sulfuric acid (v/v) at different residence times (30 and 60 min) and temperatures (110, 120 and 130°C). Higher glucose produced (0.29 g/L ) was obtained when the coconut dregs were hydrolyzed at temperature of 130°C and a residence time of 60 min. FTIR spectra revealed the degradation of the lignocelluloses chemical structure. The changes of the chemical structure of hemicelluloses and cellulose after hydrolysis obviously showed that the degradation of the polymer of carbohydrate in coconut dregs to glucose. These results of degradation of lignocelluloses compound were consistent with those from the TGA. The result from TGA analysis revealed a reduction in thermal stability of the hydrolyzed fraction compared to raw state of coconut dregs.

The Effect of Hydrochloric Acid on the Surface Area, Morphology and Physico-Chemical Properties of Sayong Kaolinite Clay

The effects of hydrochloric acid (HCL) modification of the surface area, morphology and physico-chemical properties of Sayong kaolinite clay was investigated in this study. Sayong kaolinite clay was refluxed with different concentration of HCL (1M, 5M and 10M) at 100 °C for 4 hours and followed by calcination at 500 °C at 1 hour. The samples of untreated and treated clay were characterized by different analytical equipment such as BET Surface Area Analyzer, X-Ray Fluorescence (XRF), Fourier Transform Infrared (FTIR), Thermogravimetric Analyzer (TGA) and Field Emission Scanning Electron Microscopy (FESEM). The acid treatment increased the surface area of the Sayong kaolinite clay almost three times from 24.46 m2/g to the maximum value which is 64.04 m2/g once treated with 5M HCL. The increasing of the surface area is due to the formation of amorphous silica phase and removal of the octahedral Al3+ cations and other impurities (such as Mg2+, K+, Ca+ etc.) when the acid strength is increasing as reported in XRF analysis. FTIR study shows the change of the peak intensity of several types of structural OH groups that presently in the untreated and acid treated samples. TGA-DTA profiles shows that acid treatment increased the amount of physisorbed water as the acid concentration is increased. There are three of endothermic peaks was observed in the untreated sample which centered at 49 °C, 275 °C and 520 °C. However, when the clay samples treated with acid, it has increased the physisorbed water and decreased the structural and coordinated water which caused the change in the endothermic curves in the treated sample.