Conference Publications
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PublicationNitrate and phosphate uptake dynamics in two halotolerant strains of Chlorella vulgaris is differentially influenced by carbon, nitrogen and phosphorus supply(Elsevier, 2023)Microalgae are attractive for the development of environmentally sustainable processes with the option for carbon fixation, given the photosynthetic capacity of these microorganisms. Nitrogen and phosphorus are key nutrients for microalgal growth as well as carbon fixation and product formations. These are also important nutrients in agriculture, the sustainable supply of which is a challenge. They are often lost in waste streams but can be effectively recovered using microalgae and made available for agriculture. In this investigation, we systematically examined the nitrate and phosphate uptake response of two halotolerant strains of Chlorella vulgaris exposed to four carbon and three nitrogen and phosphorus supply regimes to develop an understanding of the relationship between uptake and supply in two microalgae strains from a similar habitat. Markedly differential response to changes in carbon and nutrient supply regimes were noted between the supply regimes and the strains. Changes in carbon supply was found to significantly influence nitrogen and phosphorus uptake in the two strains. Kinetics of nutrient depletion and carbon fixation were observed to be dynamic and non-linear for both the strains, under high carbon and nutrient supply regimes. This investigation provides for the first time a clear evidence base for the role of supply regimes in the management of nutrient uptake in microalgae, including the relationship between the two, and the significance of carbon supply in nitrogen and phosphorus uptake by microalgae. This will enable development of sustainable processes and predictable strategies involving microalgae towards net-zero solutions, as well as nitrogen and phosphorus recovery from waste streams.
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PublicationIsolation and characterization of laccase secreting microorganism from Gua Kelam 2, Perlis(AIP Publishing, 2023)The current study, involves isolation and characterization of laccase producing microbes from Gua Kelam 2, Perlis, Malaysia. In our study, all isolates were cultivated on nutrient agar containing guaiacol. Only one isolate (GK1) was detected as a positive laccase producer which was then subjected for growth curve and kinetic analysis using nutrient broth and minimal salt medium. For nutrient broth, short exponential phase was recorded from 2nd h until 4th h in contrast to minimal salt medium that exhibited exponential phase from 8th h until 24th h. The highest laccase activity was recorded in nutrient broth (4.50 U L-1) at 4th h incubation compared to minimal salt medium (3.72 U L-1) at 30 h. The isolate GK1, was characterized to be rod shape and Gram positive bacterium. Based on the 16S rRNA sequencing, the isolate determined to be Bacillus subtilis.
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PublicationMechanical properties of recycled polypropylene filled with aluminium hydroxide(Trans Tech Publications Ltd., 2020)The present work aims to study the prospects of the efficient utilization of aluminium hydroxide (Al(OH)3) as a filler for thermoplastic recycled polymer. Recycled polypropylene (rPP) has been used as polymer matrix to prepare composites with different levels (25 and 50 wt.%) of aluminium hydroxide filler. Maleic anhydride-grafted polypropylene (MAPP) coupling agent has also been incorporated into rPP composites to facilitate particle dispersion. MAPP treated composites have shown up to 20% improvement in tensile strength and an increment of up to 33% in tensile modulus as compared to neat rPP prepared at 25 wt.% and 50 wt.% Al(OH)3 filler content, respectively. MAPP surface treatment enhancement of interfacial adhesion between rPP matrix and Al(OH)3 filler is evident through SEM micrographs. Al(OH)3 filler strongly influences the flammability of rPP composites, with a significant reduction in average ignition time. The flame retardancy of MAPP treated rPP composite surpasses untreated rPP composite, despite the insignificant amount of difference between the two.
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PublicationEnhancement of electrical conductivity of electrospun polyacrylonitrile fibres using carbon nanomaterials synthesised from polypropylene waste(Trans Tech Publications Ltd., 2020)Incorporation of carbon nanomaterials (CNMs) into polymer such as Polyacrylonitrile (PAN) fibres allow electric current to pass through easily. Therefore in this study, bulk quantities of CNMs are synthesised using Chemical Vapor Deposition (CVD) method by manipulating the reaction time and catalyst ratio. Polypropylene wastes are used as the carbon precursor and ferrocene as metal catalyst in the CVD experiment. Addition of 1 wt% synthesised-CNMs into electrospun PAN fibres successfully increased the electrical conductivity by 50%. Addition of CNMs improved the crystallinity of electrospun-PAN/CNMs fibres as proven by XRD analysis. Electrospun PAN/CNMs-A fibres show larger diameter than the diameter of electrospun PAN/CNMs-B. Large bead formations contained densely-packed CNMs-A within the structure of electrospun PAN/CNMs-A fibres hindered their effectiveness to conduct the electricity. On the contrary, PAN/CNMs-B shows remarkable improvement in electrical conductivity when loosely-packed CNMs-B are added to the PAN fibres.
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PublicationTensile strength on seven type of fruits skin fiber thermoplastic poyurethane (TPU)(Trans Tech Publications Ltd., 2020)Natural fibers of trees, fruit skins and so on are considered as recyclable and are used as filler materials in polymer composites. For decades, natural fibers have become the attention of researchers as an alternative to commercial, synthetic and costly fibers. Therefore, this study has used 7 types of natural fibers from local fruit waste parts in Malaysia, as fillers in TPU. This composite was produced via melt mixing technique, with different filler loading from 5wt% to 20wt%. Different types of natural fiber and its loading, showed different mechanical properties which resulted through tensile strength and elongation at break. Also, it is found that each of these natural fibers gives maximum tensile strength to the optimum loading between 5wt% and 10wt%. The composite with pineapple fiber is the composite with the highest tensile strength value at 5wt% filler load, as well as the most elastic composite with the highest elongation at break percentages.