Mohd Khan Ayob

Citric acid modified kenaf core fibres for removal of methylene blue from aqueous solution.

Chemically modified kenaf core fibres were prepared via esterification in the presence of citric acid (CA). The adsorption kinetics and isotherm studies were carried out under different conditions to examine the adsorption efficiency of CA-treated kenaf core fibres towards methylene blue (MB). The adsorption capacity of the kenaf core fibres increased significantly after the citric acid treatment. The values of the correlation coefficients indicated that the Langmuir isotherm fitted the experimental data better than the Freundlich isotherm. The maximum adsorption capacity of the CA-treated kenaf core fibres was found to be 131.6mg/g at 60°C. Kinetic models, pseudo-first-order, pseudo-second-order and intraparticle diffusion, were employed to describe the adsorption mechanism. The kinetic data were found to fit pseudo-second-order model equation as compared to pseudo-first-order model. The adsorption of MB onto the CA-treated kenaf core fibres was spontaneous and endothermic.

Antibacterial performance of Ag nanoparticles and AgGO nanocomposites prepared via rapid microwave-assisted synthesis method

Silver nanoparticles and silver-graphene oxide nanocomposites were fabricated using a rapid and green microwave irradiation synthesis method. Silver nanoparticles with narrow size distribution were formed under microwave irradiation for both samples. The silver nanoparticles were distributed randomly on the surface of graphene oxide. The Fourier transform infrared and thermogravimetry analysis results showed that the graphene oxide for the AgNP-graphene oxide (AgGO) sample was partially reduced during the in situ synthesis of silver nanoparticles. Both silver nanoparticles and AgGO nanocomposites exhibited stronger antibacterial properties against Gram-negative bacteria (Salmonella typhi and Escherichia coli) than against Gram-positive bacteria (Staphyloccocus aureus and Staphyloccocus epidermidis). The AgGO nanocomposites consisting of approximately 40 wt.% silver can achieve antibacterial performance comparable to that of neat silver nanoparticles.

Purification and characterisation of antibacterial peptide-containing compound derived from palm kernel cake

Palm kernel cake (PKC), the most useful by-product resulted from palm kernel oil production. In this study, PKC-derived protein product was found suitable for use as an antimicrobial agent with potent antibacterial activity, particularly against Bacillus species, after enzymatic hydrolysis with alcalase. The hydrolysate was further purified by gel filtration chromatography. The purified fraction was found to have 14.63±0.70% (w/w) protein, a molecular mass of 2.4kDa and low hemolytic activity (<50% hemolysis of human erythrocytes at concentration of 1000μg/ml). The presence of lysine and the major component lauric acid derivative, as indicated by electrospray ionisation-mass spectrometry (ESI-MS) direct infusion and nuclear magnetic resonance (NMR) spectroscopy, may have contributed to the antibacterial effect of purified PKC fraction. This study suggests that the antibacterial PKC compound may be not a pure peptide but instead a peptide-containing compound high in lauric acid derivative.

A graphene oxide facilitated a highly porous and effective antibacterial regenerated cellulose membrane containing stabilized silver nanoparticles

Abstract Regenerated nanocomposite cellulose membranes embedded with silver nanoparticles (AgNP) and AgNP-graphene oxide (AgGO) were prepared in this study. The as-synthesized AgNP and AgGO were added respectively to a cellulose solution that was prepared by dissolving cellulose in a precooled NaOH/urea (NU) solvent. The solution mixtures were further regenerated into nanocomposite membranes through coagulation in an acidic solution. UV-Vis and TEM results revealed the improved stability of the AgGO compared to that of the AgNP in NU solutions. As revealed by FESEM, the AgGO nanocomposite membrane possessed a more porous structure than a membrane containing AgNP. Antibacterial tests demonstrated that the cellulose membrane of AgGO inhibited the growth of both Staphylococcus aureus and Escherichia coli more effectively than the AgNP nanocomposite membrane, with a lower concentration of AgGO. This work provides a proven and effective method to prepare novel functional cellulose membranes with antibacterial properties, thus broadening the applications of cellulose.

Antibacterial activity of different degree of hydrolysis of palm kernel expeller peptides against spore-forming and non-spore-forming bacteria.

Aims:  The goal of this study was to determine inhibitory effect of palm kernel expeller (PKE) peptides of different degree of hydrolysis (DH %) against spore‐forming bacteria Bacillus cereus, Bacillus circulans, Bacillus coagulans, Bacillus licheniformis, Bacillus megaterium, Bacillus pumilus, Bacillus stearothermophillus, Bacillus subtilis, Bacillus thuringiensis, Clostridium perfringens; and non‐spore‐forming bacteria Escherichia coli, Lisinibacillus sphaericus, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella Typhimurium and Staphylococcus aureus.

Effects of encapsulation on the viability of potential probiotic Lactobacillus plantarum exposed to high acidity condition and presence of bile salts

This study investigated the survival of encapsulated potential probiotic Lactobacillus plantarum which isolated from fermented cocoa beans. κ-Carrageenan was used to encapsulate the probiotic. Encapsulation techniques such as emulsification, freeze-drying or extrusion were adopted to encapsulate the probiotic. Freeze-drying and extrusion methods showed higher (p < 0.05) efficiency (89.48 ± 3.21 and 92.26 ± 1.45%, respectively) in encapsulating the probiotic compared to the emulsification method (82.19 ± 0.71% efficiency). Freeze-dried encapsulated probiotic L. plantarum was selected for further survival analysis as greater amount of beads were produced compared to the extrusion method. Freeze-dried probiotic was found to have significantly (p < 0.05) higher tolerance to acid at pH 2 with higher survival percentage compared to non-encapsulated probiotic. However, freeze-drying encapsulation was proven not to enhance the resistance of the probiotic to bile salt as evidenced by the one log colony reduction as for the non-encapsulated probiotic. Further modification of freeze-drying encapsulation technique is needed to enhance the survival of the encapsulated potential probiotic L. plantarum toward bile salt in the future.

Silver Nanoparticles - Graphene Oxide Nanocomposite for Antibacterial Purpose

Graphene oxide (GO) sheets, a single layer of carbon atoms which can be served as substrates for fabricating metallic nanoparticles-GO nanocomposites. In this study, the nanocomposite of silver nanoparticles and graphene oxide were produced via in-situ synthesis and with the addition of chitosan to investigate the formation of silver nanoparticles on the graphene oxide sheets. XRD and UV-Vis studies confirmed the formation of silver nanoparticles on GO sheets, while TEM and FESEM images presented the loading of silver nanoparticles on the GO sheets. The degree of loading and distribution of the silver nanoparticles on the graphene oxide were depend on the method during the formation of silver nanoparticles. The nanocomposites can be potentially used in food packaging and biomedical applications.

Optimization of hexametaphosphate-assisted extraction and functional characterization of palm kernel cake protein:

Response surface methodology was applied to study the optimization of palm kernel cake protein (PKCP) hexametaphosphate-assisted extraction. The optimum PKCP yield (28.37%) when extracted using 1.50% sodium hexametaphosphate (SHMP) of pH 10, at 50 °C, and the 1:70 (w/v) ratio of cake-to-solvent was significantly (P < 0.05) higher than the protein yield from an alkaline (pH 10) extraction (8.12 ± 0.24%). Differential scanning calorimetry (DSC) analysis showed a higher denatured temperature (99.78 °C) for PKCP as compared with alkaline extracted one (96.96 °C), suggesting that a less denatured protein population is obtained. Electrophoresis of the PKCP revealed that the protein has 11 bands with MW ranging from 2.11 to 83.19 kDa. Relative to soy protein isolate, PKCP showed higher surface hydrophobicity (165.96 vs. 51.51), better solubility at pH 7 (87.65% vs. 41.21%), oil-binding capacity (7.73 vs. 2.96 g/g) and emulsifying activity (178.50 vs. 32.57 m2/g), but lower water-binding capacity (0.36 vs. 11.70 g/g), emulsifying stability (32.24% vs. 43.08%), foaming capacity (20.8% vs. 100.0%) and foam stability (3.80 vs. 19.20 ml). PKCP contained the highest amount of glutamic acid (16.86 g/100 g protein) and followed by arginine (10.78 g/100 g protein). With respect to the 1991 standard of the FAO/WHO for preschool children, PKCP’s essential amino acid profile showed deficiencies. Therefore, it can be used as a complementary protein source by supplementing with a tryptophan-rich source, as this was the limiting amino acid.