Publication

1.	Norhayati Abdullah; Ali Yuzir; Thomas P. Curtis, Adibah Yahya; Zaini Ujang Characterization of aerobic granular sludge treating high strength agro-based wastewater at different volumetric loadings. J Bioresource Technology 127 181-187, 2013 DOI:10.1016/j.biortech.2012.09.047 View abstract Understanding the relationship between microbial community and mechanism of aerobic granulation could enable wider applications of granules for high-strength wastewater treatment. The majority of granulation studies principally determine the engineering aspects of granules formation with little emphasis on the microbial diversity. In this study, three identical reactors namely R1, R2 and R3 were operated using POME at volumetric loadings of 1.5, 2.5 and 3.5 kg COD m3 d1, respectively. Aeration was provided at a volumetric flow rate of 2.5 cm s1. Aerobic granules were successfully developed in R2 and R3 while bioflocs dominated R1 until the end of experiments. Fractal dimension (Df) averaged at 1.90 suggesting good compactness of granules. The PCR–DGGE results indicated microbial evolutionary shift throughout granulation despite different operating OLRs based on decreased Raup and Crick similarity indices upon mature granule formation. The characteristics of aerobic granules treating high strength agro-based wastewater are determined at different volumetric loadings.
2.	Yi-Fan Goh a, Ammar Z. Alshemary a, Muhammad Akram a, Mohammed Rafiq Abdul Kadir b, Rafaqat Hussain In vitro study of nano-sized zinc doped bioactive glass. J Materials Chemistry and Physics 137 1031-1038, 2013 DOI:10.1016/j.matchemphys.2012.11.022 View abstract Surface reactivity in physiological fluid has been linked to bioactivity of a material. Past research has shown that bioactive glass containing zinc has the potential in bone regeneration field due to its enhanced bioactivity. However, results from literature are always contradictory. Therefore, in this study, surface reactivity of bioactive glass containing zinc was evaluated through the study of morphology and composition of apatite layer formed after immersion in simulated body fluid (SBF). Nano-sized bioactive glass with 5 and 10 mol% zinc were synthesized through quick alkali solegel method. The synthesized Zn ebioglass was characterized using field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrometer (EDX), X-ray diffractometer (XRD) and Fourier transform infrared spectrometer (FTIR). Samples after SBF immersion were characterized using scanning electron microscope (SEM) and EDX. Morphological study through SEM showed the formation of spherical apatite particles with Ca/P ratio closer to 1.67 on the surface of 5 mol% Znebioglass. Whereas, the 10 mol% Znebioglass samples induced the formation of flake-like structure of calcite in addition to the spherical apatite particles with much higher Ca/P ratio. Our results suggest that the higher Zn content increases the bioactivity through the formation of bone-bonding calcite as well as the spherical apatite particles.
3.	Hassan Jafari, Mohd Hasbullah Idris, Ali Ourdjini, Mohammed Rafiq Abdul Kadir An investigation on interfacial reaction between in-situ melted AZ91D magnesium alloy and ceramic shell mold during investment casting process. J Materials Chemistry and Physics xxx 1-1, 2013 DOI:10.1016/j.matchemphys.2012.12.037 View abstract The reaction between ceramic shell investment mold and AZ91D magnesium alloy as well as the related mechanism involved during investment casting process using in-situ melting technique were explored. AZ91D granules were melted in a ceramic shell investment casting mold at 750 C in an argon protected environment and a melting flux. The interface of adhered investment-AZ91D cast alloy and the residues that appeared on the surface of the castings, as the moldemetal reaction products, were analyzed to determine the morphology, elements and compounds that may have developed due to the reactions. It was discovered that the high process temperature and high affinity of magnesium with oxygen developed cracks in the ceramic shell investment mold. Penetration of molten metal through the cracks also occurred and caused adherence of investment on the casting surface. The results showed that the black residue with a granular morphology has the same microstructure as that of AZ91D alloy and also comprises of MgO and Mg2Si on its surface. The findings revealed that two types of products formed on the shell surface due to the moldemetal reaction. The first product formed on the surface as a result of the reaction between AZ91D alloy and the binder producing MgO and MgAl2O4. The second product formed because of the penetration of Mg into the ceramic shell investment mold followed by reaction with oxygen bearing materials forming MgO and Mg2Si.
4.	Mohd Firdaus Abdul-Wahab, Giek Far Chan, Abdull Rahim Mohd Yusoff, Noor Aini Abdul Rashid Reduction of azo dyes by flavin reductase from Citrobacter freundii A1. J Xenobiotics 3:e2 9-13, 2013 DOI:10.4081/xeno.2013.e2 View abstract Citrobacter freundii A1 isolated from a sewage treatment facility was demonstrated to be able to effectively decolorize azo dyes as pure and mixed culture. This study reports on the investigation on the enzymatic systems involved. An assay performed suggested the possible involvement of flavin reductase (Fre) as an azo reductase. A heterologouslyexpressed recombinant Fre from C. freundii A1 was used to investigate its involvement in the azo reduction process. Three model dyes were used, namely Acid Red 27 (AR27), Direct Blue 15 (DB15) and Reactive Black 5 (RB5). AR27 was found to be reduced the fastest by Fre, followed by RB5, and lastly DB15. Redox mediators nicotinamide adenine dinucleotide (NADH) and riboflavin enhance the reduction, suggesting the redox activity of the enzyme. The rate and extent of reduction of the model dyes correlate well with the reduction potentials (Ep). The data presented here strongly suggest that Fre is one of the enzymes responsible for azo reduction in C. freundii A1, acting via an oxidation-reduction reaction.
5.	Nonlawat Boonyalai,  James R. Pullen, Mohd Firdaus Abdul wahab, Michael Wright, Andrew D. Miller Escherichia coli LysU is a potential surrogate for human lyslyl tRNA synthetase in interactions with the C-terminal domain of HIV-1 capsid protein. J The Royal Society of Chemistry 11 612-620, 2013 DOI:10.1039/c2ob26499d View abstract Human lysyl-tRNA synthetase (hLysRS) is known to interact directly with human immunodeficiency virus type-1 (HIV-1) GagPol polyproteins, and both hLysRS with tRNALys3 are selectively packaged into emerging HIV-1 viral particles. This packaging process appears to be mediated by contact between the motif 1 helix h7 of hLysRS and the C-terminal dimerization domain of the HIV-1 capsid protein (CA) segment of Gag or GagPol. Given similarities between hLysRS and Escherichia coli (E. coli) heat shock protein LysU, we investigate if LysU might be an hLysRS surrogate for interactions with Gag or GagPol proteins. We report on a series of studies involving three CA C-domains: CA146 (intact domain), CA151 (truncated domain), and CA146-M185A (M185A, CA dimer interface mutant). After confirming that LysU and CA146 are dimeric whilst CA151 and M185A remain monomeric, we use glutathione S-transferase (GST) pulldown assays to demonstrate the existence of specific interactions between LysU and all three CA-C domains. By means of 1H-NMR titration experiments, we estimate Kd values of 50 μM for the interaction between LysU and CA146 or >500 μM for interactions between LysU and CA151 or LysU and M185A. The reason for these binding affinity differences may be that interactions between LysU and CA146 take place through dimer–dimer interactions resulting in a α2β2 heterotetramer. LysU/CA-C protein interactions are weaker than those reported between hLysRS and the Gag, CA or CA146 proteins, and hLysRS/Gag binding interactions have also been suggested to involve only αβ heterodimer formation. Nevertheless, we propose that LysU could act as a surrogate for hLysRS with respect to Gag and GagPol polyprotein interactions although arguably not sufficiently for LysU to act as an inhibitor of the HIV-1 life cycle without further adaptation or mutation. Potentially, LysU and/or LysU mutants could represent a new class of anti-HIV-1 therapeutic agent