Displaying publications 1 - 20 of 81 in total

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  1. Establishing and managing a periodontal biobank for research: the sharing of experience
    Vaithilingam RD, Safii SH, Baharuddin NA, Karen-Ng LP, Saub R, Ariffin F, et al.
    Oral Dis, 2015 Jan;21(1):e62-9.
    PMID: 24930489 DOI: 10.1111/odi.12267
    Periodontal bio-repositories, which allow banking of clinically validated human data and biological samples, provide an opportunity to derive biomarkers for periodontal diagnosis, prognosis and therapeutic activities which are expected to improve patient management. This article presents the establishing of the Malaysian Periodontal Database and Biobank System (MPDBS) which was initiated in 2011 with the aim to facilitate periodontal research. Partnerships were established with collaborating centres. Policies on specimen access, authorship and acknowledgement policies were agreed upon by all participating centres before the initiation of the periodontal biobank. Ethical approval for the collection of samples and data were obtained from institutional ethics review boards. A broad-based approach for informed consent was used, which covered areas related to quality of life impacts, genetics and molecular aspects of periodontal disease. Sample collection and processing was performed using a standardized protocol. Biobanking resources such as equipment and freezers were shared with the Malaysian Oral Cancer Database and Tissue Bank System (MOCDTBS). In the development of the MPDBS, challenges that were previously faced by the MOCDTBS were considered. Future challenges in terms of ethical and legal issues will be faced when international collaborations necessitate the transportation of specimens across borders.
  2. Fulltext Hell's Gate globin I: an acid and thermostable bacterial hemoglobin resembling mammalian neuroglobin
    Teh AH, Saito JA, Baharuddin A, Tuckerman JR, Newhouse JS, Kanbe M, et al.
    FEBS Lett., 2011 Oct 20;585(20):3250-8.
    PMID: 21925500 DOI: 10.1016/j.febslet.2011.09.002
    Hell's Gate globin I (HGbI), a heme-containing protein structurally homologous to mammalian neuroglobins, has been identified from an acidophilic and thermophilic obligate methanotroph, Methylacidiphilum infernorum. HGbI has very high affinity for O(2) and shows barely detectable autoxidation in the pH range of 5.2-8.6 and temperature range of 25-50°C. Examination of the heme pocket by X-ray crystallography and molecular dynamics showed that conformational movements of Tyr29(B10) and Gln50(E7), as well as structural flexibility of the GH loop and H-helix, may play a role in modulating its ligand binding behavior. Bacterial HGbI's unique resistance to the sort of extreme acidity that would extract heme from any other hemoglobin makes it an ideal candidate for comparative structure-function studies of the expanding globin superfamily.
  3. Primary recovery of a bacteriocin-like inhibitory substance derived from Pediococcus acidilactici Kp10 by an aqueous two-phase system
    Abbasiliasi S, Tan JS, Ibrahim TA, Kadkhodaei S, Ng HS, Vakhshiteh F, et al.
    Food Chem, 2014 May 15;151:93-100.
    PMID: 24423507 DOI: 10.1016/j.foodchem.2013.11.019
    A polymer-salt aqueous two-phase system (ATPS) consisting of polyethylene-glycol (PEG) with sodium citrate was developed for direct recovery of a bacteriocin-like inhibitory substance (BLIS) from a culture of Pediococcus acidilactici Kp10. The influences of phase composition, tie-line length (TLL), volume ratio (VR), crude sample loading, pH and sodium chloride (NaCl) on the partition behaviour of BLIS was investigated. Under optimum conditions of ATPS, the purification of BLIS was achieved at 26.5% PEG (8000)/11% sodium citrate with a TLL of 46.38% (w/w), VR of 1.8, and 1.8% crude load at pH 7 without the presence of NaCl. BLIS from P. acidilactici Kp10 was successfully purified by the ATPS up to 8.43-fold with a yield of 81.18%. Given that the operation of ATPS is simple, environmentally friendly and cost-effective, as it requires only salts and PEG, it may have potential for industrial applications in the recovery of BLIS from fermentation broth.
  4. A Review of Gene Knockout Strategies for Microbial Cells
    Tang PW, Chua PS, Chong SK, Mohamad MS, Choon YW, Deris S, et al.
    Recent Pat Biotechnol, 2015;9(3):176-97.
    PMID: 27185502
    BACKGROUND: Predicting the effects of genetic modification is difficult due to the complexity of metabolic net- works. Various gene knockout strategies have been utilised to deactivate specific genes in order to determine the effects of these genes on the function of microbes. Deactivation of genes can lead to deletion of certain proteins and functions. Through these strategies, the associated function of a deleted gene can be identified from the metabolic networks.

    METHODS: The main aim of this paper is to review the available techniques in gene knockout strategies for microbial cells. The review is done in terms of their methodology, recent applications in microbial cells. In addition, the advantages and disadvantages of the techniques are compared and discuss and the related patents are also listed as well.

    RESULTS: Traditionally, gene knockout is done through wet lab (in vivo) techniques, which were conducted through laboratory experiments. However, these techniques are costly and time consuming. Hence, various dry lab (in silico) techniques, where are conducted using computational approaches, have been developed to surmount these problem.

    CONCLUSION: The development of numerous techniques for gene knockout in microbial cells has brought many advancements in the study of gene functions. Based on the literatures, we found that the gene knockout strategies currently used are sensibly implemented with regard to their benefits.

  5. Tropical soil bacterial communities in Malaysia: pH dominates in the equatorial tropics too
    Tripathi BM, Kim M, Singh D, Lee-Cruz L, Lai-Hoe A, Ainuddin AN, et al.
    Microb Ecol, 2012 Aug;64(2):474-84.
    PMID: 22395784 DOI: 10.1007/s00248-012-0028-8
    The dominant factors controlling soil bacterial community variation within the tropics are poorly known. We sampled soils across a range of land use types--primary (unlogged) and logged forests and crop and pasture lands in Malaysia. PCR-amplified soil DNA for the bacterial 16S rRNA gene targeting the V1-V3 region was pyrosequenced using the 454 Roche machine. We found that land use in itself has a weak but significant effect on the bacterial community composition. However, bacterial community composition and diversity was strongly correlated with soil properties, especially soil pH, total carbon, and C/N ratio. Soil pH was the best predictor of bacterial community composition and diversity across the various land use types, with the highest diversity close to neutral pH values. In addition, variation in phylogenetic structure of dominant lineages (Alphaproteobacteria, Beta/Gammaproteobacteria, Acidobacteria, and Actinobacteria) is also significantly correlated with soil pH. Together, these results confirm the importance of soil pH in structuring soil bacterial communities in Southeast Asia. Our results also suggest that unlike the general diversity pattern found for larger organisms, primary tropical forest is no richer in operational taxonomic units of soil bacteria than logged forest, and agricultural land (crop and pasture) is actually richer than primary forest, partly due to selection of more fertile soils that have higher pH for agriculture and the effects of soil liming raising pH.
  6. Fulltext The Discovery of New Antilisterial Proteins From Paenibacillus polymyxa Kp10 via Genome Mining and Mass Spectrometry
    Mokhtar NFK, Hashim AM, Hanish I, Zulkarnain A, Raja Nhari RMH, Abdul Sani AA, et al.
    Front Microbiol, 2020;11:960.
    PMID: 32714281 DOI: 10.3389/fmicb.2020.00960
    The inhibitory properties of novel antimicrobial proteins against food-borne pathogens such as Listeria monocytogenes offer extensive benefits to the food and medical industries. In this study, we have identified antimicrobial proteins from a milk curd-derived bacterial isolate that exhibits antilisterial activity using genome mining and mass spectrometry analysis. The analysis of the draft genome sequence identified the isolate as Paenibacillus polymyxa Kp10, and predicted the presence of antimicrobial paenibacillin, paenilan, paeninodin, sactipeptides, thiazole-oxazole modified microcin, and histone-like DNA binding protein HU encoded in its genome. Interestingly, nanoLC-MS/MS analysis identified two histone-like DNA binding proteins HU as predicted in silico earlier, exhibiting antilisterial activity. Additionally, translation initiation factor IF-1 and 50S ribosomal protein L29 were also discovered by the mass spectrometry in the active fractions. The antilisterial activity of the four proteins was verified through heterologous protein expression and antimicrobial activity assay in vitro. This study has identified structural regulatory proteins from Paenibacillus possessing antilisterial activity with potential future application in the food and medical industries.
  7. Fulltext Growth phase-dependent proteomes of the Malaysian isolated Lactococcus lactis dairy strain M4 using label-free qualitative shotgun proteomics analysis
    Yap TW, Rabu A, Abu Bakar FD, Rahim RA, Mahadi NM, Illias RM, et al.
    ScientificWorldJournal, 2014;2014:642891.
    PMID: 24982972 DOI: 10.1155/2014/642891
    Lactococcus lactis is the most studied mesophilic fermentative lactic acid bacterium. It is used extensively in the food industry and plays a pivotal role as a cell factory and also as vaccine delivery platforms. The proteome of the Malaysian isolated L. lactis M4 dairy strain, obtained from the milk of locally bred cows, was studied to elucidate the physiological changes occurring between the growth phases of this bacterium. In this study, ultraperformance liquid chromatography nanoflow electrospray ionization tandem mass spectrometry (UPLC- nano-ESI-MS(E)) approach was used for qualitative proteomic analysis. A total of 100 and 121 proteins were identified from the midexponential and early stationary growth phases, respectively, of the L. lactis strain M4. During the exponential phase, the most important reaction was the generation of sufficient energy, whereas, in the early stationary phase, the metabolic energy pathways decreased and the biosynthesis of proteins became more important. Thus, the metabolism of the cells shifted from energy production in the exponential phase to the synthesis of macromolecules in the stationary phase. The resultant proteomes are essential in providing an improved view of the cellular machinery of L. lactis during the transition of growth phases and hence provide insight into various biotechnological applications.
  8. Fulltext Optimization of a heterologous signal peptide by site-directed mutagenesis for improved secretion of recombinant proteins in Escherichia coli
    Jonet MA, Mahadi NM, Murad AM, Rabu A, Bakar FD, Rahim RA, et al.
    J. Mol. Microbiol. Biotechnol., 2012;22(1):48-58.
    PMID: 22456489 DOI: 10.1159/000336524
    A heterologous signal peptide (SP) from Bacillus sp. G1 was optimized for secretion of recombinant cyclodextrin glucanotransferase (CGTase) to the periplasmic and, eventually, extracellular space of Escherichia coli. Eight mutant SPs were constructed using site-directed mutagenesis to improve the secretion of recombinant CGTase. M5 is a mutated SP in which replacement of an isoleucine residue in the h-region to glycine created a helix-breaking or G-turn motif with decreased hydrophobicity. The mutant SP resulted in 110 and 94% increases in periplasmic and extracellular recombinant CGTase, respectively, compared to the wild-type SP at a similar level of cell lysis. The formation of intracellular inclusion bodies was also reduced, as determined by sodium dodecyl sulfate-polyacrylamyde gel electrophoresis, when this mutated SP was used. The addition of as low as 0.08% glycine at the beginning of cell growth improved cell viability of the E. coli host. Secretory production of other proteins, such as mannosidase, also showed similar improvement, as demonstrated by CGTase production, suggesting that the combination of an optimized SP and a suitable chemical additive leads to significant improvements of extracellular recombinant protein production and cell viability. These findings will be valuable for the extracellular production of recombinant proteins in E. coli.
  9. Detection of Vibrio parahaemolyticus in cockle (Anadara granosa) by PCR
    Bilung LM, Radu S, Bahaman AR, Rahim RA, Napis S, Ling MW, et al.
    FEMS Microbiol Lett, 2005 Nov 1;252(1):85-8.
    PMID: 16216442
    This study aimed to determine the occurrence of Vibrio parahaemolyticus in cockles (Anadara granosa) at a harvesting area and to detect the presence of virulent strains carrying the thermostable direct hemolysin (tdh) and TDH-related hemolysin genes (trh) using PCR. Of 100 samples, 62 were positive for the presence of V. parahaemolyticus with an MPN (most probable number) value greater than 3.0 (>1100 MPN per g). The PCR analysis revealed 2 samples to be positive for the tdh gene and 11 to be positive for the trh gene. Hence, these results demonstrate the presence of pathogenic V. parahaemolyticus in cockles harvested in the study area and reveal the potential risk of illness associated with their consumption.
  10. Fulltext Characterization of Gold-Sputtered Zinc Oxide Nanorods-a Potential Hybrid Material
    Perumal V, Hashim U, Gopinath SC, Rajintra Prasad H, Wei-Wen L, Balakrishnan SR, et al.
    Nanoscale Res Lett, 2016 Dec;11(1):31.
    PMID: 26787050 DOI: 10.1186/s11671-016-1245-8
    Generation of hybrid nanostructures has been attested as a promising approach to develop high-performance sensing substrates. Herein, hybrid zinc oxide (ZnO) nanorod dopants with different gold (Au) thicknesses were grown on silicon wafer and studied for their impact on physical, optical and electrical characteristics. Structural patterns displayed that ZnO crystal lattice is in preferred c-axis orientation and proved the higher purities. Observations under field emission scanning electron microscopy revealed the coverage of ZnO nanorods by Au-spots having diameters in the average ranges of 5-10 nm, as determined under transmission electron microscopy. Impedance spectroscopic analysis of Au-sputtered ZnO nanorods was carried out in the frequency range of 1 to 100 MHz with applied AC amplitude of 1 V RMS. The obtained results showed significant changes in the electrical properties (conductance and dielectric constant) with nanostructures. A clear demonstration with 30-nm thickness of Au-sputtering was apparent to be ideal for downstream applications, due to the lowest variation in resistance value of grain boundary, which has dynamic and superior characteristics.
  11. An effective extracellular protein secretion by an ABC transporter system in Escherichia coli: statistical modeling and optimization of cyclodextrin glucanotransferase secretory production
    Low KO, Mahadi NM, Rahim RA, Rabu A, Abu Bakar FD, Murad AM, et al.
    J Ind Microbiol Biotechnol, 2011 Sep;38(9):1587-97.
    PMID: 21336875 DOI: 10.1007/s10295-011-0949-0
    Direct transport of recombinant protein from cytosol to extracellular medium offers great advantages, such as high specific activity and a simple purification step. This work presents an investigation on the potential of an ABC (ATP-binding cassette) transporter system, the hemolysin transport system, for efficient protein secretion in Escherichia coli (E. coli). A higher secretory production of recombinant cyclodextrin glucanotransferase (CGTase) was achieved by a new plasmid design and subsequently by optimization of culture conditions via central composite design. An improvement of at least fourfold extracellular recombinant CGTase was obtained using the new plasmid design. The optimization process consisted of 20 experiments involving six star points and six replicates at the central point. The predicted optimum culture conditions for maximum recombinant CGTase secretion were found to be 25.76 μM IPTG, 1.0% (w/v) arabinose and 34.7°C post-induction temperature, with a predicted extracellular CGTase activity of 68.76 U/ml. Validation of the model gave an extracellular CGTase activity of 69.15 ± 0.71 U/ml, resulting in a 3.45-fold increase compared to the initial conditions. This corresponded to an extracellular CGTase yield of about 0.58 mg/l. We showed that a synergistic balance of transported protein and secretory pathway is important for efficient protein transport. In addition, we also demonstrated the first successful removal of the C-terminal secretion signal from the transported fusion protein by thrombin proteolytic cleavage.
  12. Distinctive bacterial communities in the rhizoplane of four tropical tree species
    Oh YM, Kim M, Lee-Cruz L, Lai-Hoe A, Go R, Ainuddin N, et al.
    Microb Ecol, 2012 Nov;64(4):1018-27.
    PMID: 22767122 DOI: 10.1007/s00248-012-0082-2
    It is known that the microbial community of the rhizosphere is not only influenced by factors such as root exudates, phenology, and nutrient uptake but also by the plant species. However, studies of bacterial communities associated with tropical rainforest tree root surfaces, or rhizoplane, are lacking. Here, we analyzed the bacterial community of root surfaces of four species of native trees, Agathis borneensis, Dipterocarpus kerrii, Dyera costulata, and Gnetum gnemon, and nearby bulk soils, in a rainforest arboretum in Malaysia, using 454 pyrosequencing of the 16S rRNA gene. The rhizoplane bacterial communities for each of the four tree species sampled clustered separately from one another on an ordination, suggesting that these assemblages are linked to chemical and biological characteristics of the host or possibly to the mycorrhizal fungi present. Bacterial communities of the rhizoplane had various similarities to surrounding bulk soils. Acidobacteria, Alphaproteobacteria, and Betaproteobacteria were dominant in rhizoplane communities and in bulk soils from the same depth (0-10 cm). In contrast, the relative abundance of certain bacterial lineages on the rhizoplane was different from that in bulk soils: Bacteroidetes and Betaproteobacteria, which are known as copiotrophs, were much more abundant in the rhizoplane in comparison to bulk soil. At the genus level, Burkholderia, Acidobacterium, Dyella, and Edaphobacter were more abundant in the rhizoplane. Burkholderia, which are known as both pathogens and mutualists of plants, were especially abundant on the rhizoplane of all tree species sampled. The Burkholderia species present included known mutualists of tropical crops and also known N fixers. The host-specific character of tropical tree rhizoplane bacterial communities may have implications for understanding nutrient cycling, recruitment, and structuring of tree species diversity in tropical forests. Such understanding may prove to be useful in both tropical forestry and conservation.
  13. Fulltext Isolation of Pediococcus acidilactici Kp10 with ability to secrete bacteriocin-like inhibitory substance from milk products for applications in food industry
    Abbasiliasi S, Tan JS, Ibrahim TA, Ramanan RN, Vakhshiteh F, Mustafa S, et al.
    BMC Microbiol, 2012;12:260.
    PMID: 23153191 DOI: 10.1186/1471-2180-12-260
    Lactic acid bacteria (LAB) can be isolated from traditional milk products. LAB that secrete substances that inhibit pathogenic bacteria and are resistant to acid, bile, and pepsin but not vancomycin may have potential in food applications.
  14. Fulltext Genomic analyses of two novel biofilm-degrading methicillin-resistant Staphylococcus aureus phages
    Dakheel KH, Rahim RA, Neela VK, Al-Obaidi JR, Hun TG, Isa MNM, et al.
    BMC Microbiol, 2019 05 28;19(1):114.
    PMID: 31138130 DOI: 10.1186/s12866-019-1484-9
    BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) biofilm producers represent an important etiological agent of many chronic human infections. Antibiotics and host immune responses are largely ineffective against bacteria within biofilms. Alternative actions and novel antimicrobials should be considered. In this context, the use of phages to destroy MRSA biofilms presents an innovative alternative mechanism.

    RESULTS: Twenty-five MRSA biofilm producers were used as substrates to isolate MRSA-specific phages. Despite the difficulties in obtaining an isolate of this phage, two phages (UPMK_1 and UPMK_2) were isolated. Both phages varied in their ability to produce halos around their plaques, host infectivity, one-step growth curves, and electron microscopy features. Furthermore, both phages demonstrated antagonistic infectivity on planktonic cultures. This was validated in an in vitro static biofilm assay (in microtiter-plates), followed by the visualization of the biofilm architecture in situ via confocal laser scanning microscopy before and after phage infection, and further supported by phages genome analysis. The UPMK_1 genome comprised 152,788 bp coding for 155 putative open reading frames (ORFs), and its genome characteristics were between the Myoviridae and Siphoviridae family, though the morphological features confined it more to the Siphoviridae family. The UPMK_2 has 40,955 bp with 62 putative ORFs; morphologically, it presented the features of the Podoviridae though its genome did not show similarity with any of the S. aureus in the Podoviridae family. Both phages possess lytic enzymes that were associated with a high ability to degrade biofilms as shown in the microtiter plate and CLSM analyses.

    CONCLUSIONS: The present work addressed the possibility of using phages as potential biocontrol agents for biofilm-producing MRSA.

  15. Association of social support and quality of life among people with schizophrenia receiving community psychiatric service: A cross-sectional study
    Munikanan T, Midin M, Daud TIM, Rahim RA, Bakar AKA, Jaafar NRN, et al.
    Compr Psychiatry, 2017 05;75:94-102.
    PMID: 28342379 DOI: 10.1016/j.comppsych.2017.02.009
    OBJECTIVE: To understand the needs of patients with schizophrenia for recovery, this study examined the type and level of social support and its association with quality of life (QOL) among this group of patients in the city of Kuala Lumpur.

    METHOD: A cross-sectional study was conducted on 160 individuals with schizophrenia receiving community psychiatric services in Hospital Kuala Lumpur (HKL). The WHOQOL-BREF, Brief Psychiatric Rating Scale (BPRS) and Multidimensional Scale of Perceived Social Support (MSPSS) were used to assess QOL, severity of symptoms and social support, respectively. The study respondents were predominantly Malay, aged less than 40, males, single, unmarried, had lower education levels and unemployed.

    RESULTS: About 72% of the respondents had poor perceived social support, with support from significant others being the lowest, followed by friends and family. From multiple regression analysis, social support (total, friend and family) significantly predicted better QOL in all domains; [B=0.315 (p<0.001), B=0.670 (p<0.001), B=0.257 (p<0.031)] respectively in Physical Domain; [B=0.491 (p<0.001), B=0.735 (p<0.001), B=0.631 (p<0.001)] in Psychological Domain; [B=1.065 (p<0.001), B=0.670 (p<0.017), B=2.076 (p<0.001)] in Social Domain and; [B=0.652 (p<0.001), B=1.199 (p<0.001), B=0.678 (p<0.001)] in Environmental Domain. Being married and having shorter duration of illness, lower BPRS (total) scores, female gender and smoking, were also found to significantly predict higher QOL.

    CONCLUSION: Social support is an important missing component among people with schizophrenia who are already receiving formal psychiatric services in Malaysia.

  16. Fulltext Current and Potential Developments of Cortisol Aptasensing towards Point-of-Care Diagnostics (POTC)
    Zainol Abidin AS, Rahim RA, Md Arshad MK, Fatin Nabilah MF, Voon CH, Tang TH, et al.
    Sensors (Basel), 2017 May 22;17(5).
    PMID: 28531146 DOI: 10.3390/s17051180
    Anxiety is a psychological problem that often emerges during the normal course of human life. The detection of anxiety often involves a physical exam and a self-reporting questionnaire. However, these approaches have limitations, as the data might lack reliability and consistency upon application to the same population over time. Furthermore, there might be varying understanding and interpretations of the particular question by the participant, which necessitating the approach of using biomarker-based measurement for stress diagnosis. The most prominent biomarker related to stress, hormone cortisol, plays a key role in the fight-or-flight situation, alters the immune response, and suppresses the digestive and the reproductive systems. We have taken the endeavour to review the available aptamer-based biosensor (aptasensor) for cortisol detection. The potential point-of-care diagnostic strategies that could be harnessed for the aptasensing of cortisol were also envisaged.
  17. Fulltext Inhibition of pathogenic and spoilage bacteria by a novel biofilm-forming Lactobacillus isolate: a potential host for the expression of heterologous proteins
    Jalilsood T, Baradaran A, Song AA, Foo HL, Mustafa S, Saad WZ, et al.
    Microb Cell Fact, 2015;14:96.
    PMID: 26150120 DOI: 10.1186/s12934-015-0283-8
    Bacterial biofilms are a preferred mode of growth for many types of microorganisms in their natural environments. The ability of pathogens to integrate within a biofilm is pivotal to their survival. The possibility of biofilm formation in Lactobacillus communities is also important in various industrial and medical settings. Lactobacilli can eliminate the colonization of different pathogenic microorganisms. Alternatively, new opportunities are now arising with the rapidly expanding potential of lactic acid bacteria biofilms as bio-control agents against food-borne pathogens.
  18. Effect of annealing temperature on antimicrobial and structural properties of bio-synthesized zinc oxide nanoparticles using flower extract of Anchusa italica
    Azizi S, Mohamad R, Bahadoran A, Bayat S, Rahim RA, Ariff A, et al.
    J. Photochem. Photobiol. B, Biol., 2016 Aug;161:441-9.
    PMID: 27318600 DOI: 10.1016/j.jphotobiol.2016.06.007
    The use of nontoxic biological compounds in the synthesis of nanomaterials is an economic and eco-friendly approach. The present work was undertaken to develop zinc oxide nanoparticles (ZnO-NPs) by a green method using simple precursor from the solution consisting of zinc acetate and the flower extract of Anchusa italica (A. italica). Effect of annealing temperature on structural and antimicrobial properties was investigated. The crystalline structure of ZnO-NPs was shown using X-ray diffraction (XRD) analysis. Transmission electron microscopy (TEM) results showed that ZnO-NPs are hexagonal in shapes with mean particle size of ~8 and ~14nm at 100°C and 200°C annealing temperatures respectively. The optical band gap was increased from 3.27eV to 3.30eV with the decreasing of the particle size. The antimicrobial activity of ZnO-NPs towards Gram positive (Bacillus megaterium and Stapphylococcus aureus) and Gram negative (Escherichia coli and Salmonella typhimurium) pathogens decreased with the increasing of the heat treating temperature. In vitro cytotoxicity studies on Vero cells, a dose dependent toxicity with non-toxic effect of concentration below 142μg/mL was shown. The results indicated that A. italica is an appropriate reaction media to prepare ZnO-NPs for cosmetic and bio-medical productions.
  19. Fulltext Overexpression and optimization of glutamate decarboxylase in Lactobacillus plantarum Taj-Apis362 for high gamma-aminobutyric acid production
    Tajabadi N, Baradaran A, Ebrahimpour A, Rahim RA, Bakar FA, Manap MY, et al.
    Microb Biotechnol, 2015 Jul;8(4):623-32.
    PMID: 25757029 DOI: 10.1111/1751-7915.12254
    Gamma-aminobutyric acid (GABA) is an important bioactive compound biosynthesized by microorganisms through decarboxylation of glutamate by glutamate decarboxylase (GAD). In this study, a full-length GAD gene was obtained by cloning the template deoxyribonucleic acid to pTZ57R/T vector. The open reading frame of the GAD gene showed the cloned gene was composed of 1410 nucleotides and encoded a 469 amino acids protein. To improve the GABA-production, the GAD gene was cloned into pMG36e-LbGAD, and then expressed in Lactobacillus plantarum Taj-Apis362 cells. The overexpression was confirmed by SDS-PAGE and GAD activity, showing a 53 KDa protein with the enzyme activity increased by sevenfold compared with the original GAD activity. The optimal fermentation conditions for GABA production established using response surface methodology were at glutamic acid concentration of 497.973 mM, temperature 36°C, pH 5.31 and time 60 h. Under the conditions, maximum GABA concentration obtained (11.09 mM) was comparable with the predicted value by the model at 11.23 mM. To our knowledge, this is the first report of successful cloning (clone-back) and overexpression of the LbGAD gene from L. plantarum to L. plantarum cells. The recombinant Lactobacillus could be used as a starter culture for direct incorporation into a food system during fermentation for production of GABA-rich products.
  20. Fulltext Engineering the lactococcal mevalonate pathway for increased sesquiterpene production
    Song AA, Abdullah JO, Abdullah MP, Shafee N, Othman R, Noor NM, et al.
    FEMS Microbiol Lett, 2014 Jun;355(2):177-84.
    PMID: 24828482 DOI: 10.1111/1574-6968.12469
    Isoprenoids are a large, diverse group of secondary metabolites which has recently raised a renewed research interest due to genetic engineering advances, allowing specific isoprenoids to be produced and characterized in heterologous hosts. Many researches on metabolic engineering of heterologous hosts for increased isoprenoid production are focussed on Escherichia coli and yeasts. E. coli, as most prokaryotes, use the 2-C-methyl-d-erythritol-4-phosphate (MEP) pathway for isoprenoid production. Yeasts on the other hand, use the mevalonate pathway which is commonly found in eukaryotes. However, Lactococcus lactis is an attractive alternative host for heterologous isoprenoid production. Apart from being food-grade, this Gram-positive prokaryote uses the mevalonate pathway for isoprenoid production instead of the MEP pathway. Previous studies have shown that L. lactis is able to produce sesquiterpenes through heterologous expression of plant sesquiterpene synthases. In this work, we analysed the gene expression of the lactococcal mevalonate pathway through RT-qPCR to successfully engineer L. lactis as an efficient host for isoprenoid production. We then overexpressed the mvk gene singly or co-expressed with the mvaA gene as an attempt to increase β-sesquiphellandrene production in L. lactis. It was observed that co-expression of mvk with mvaA doubled the amount of β-sesquiphellandrene produced.
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