Publications by authors named "Amal M Hashem"

13 Publications

  • Page 1 of 1

Microbiological and environmental assessment of human oral dental plaque isolates.

Microb Pathog 2019 Oct 17;135:103626. Epub 2019 Jul 17.

Chemistry of Natural and Microbial Products Department, Pharmaceutical and Drug Industries Research Division, National Research Centre, 33 El-Buhouth St. (Former El Tahrir St), 12622, Dokki, Cairo, Egypt. Electronic address:

Plaque-related diseases are amongst the most common ailments of the oral cavity. Streptococcus mutans is the causal agent of dental caries in animals and humans and is responsible for the formation and accumulation of plaques. This study aimed to identify and evaluate the role of the dental plaque isolates and its surrounding environment in plaque formation or inhibition. The study started with the identification of human dental plaque isolates from high caries index patients based on 16S rRNA and Mitis salivarius bacitracin agar (MSB) was used for S. mutans growing. Unexpectedly, the Streptococcus mutans was completely absent. The disc diffusion assay recorded that all the isolates had antimicrobial activity against the S. mutans growth. Enzymes assay revealed that the isolates produced dextransucrase, levansucrase and levanase activity with wide variation degrees. Also, the lactic acid production assay was done based in pH shift assessment. The highest pH shift and dextran yield were detected by the isolates Bacillus subtilis_AG1 and Bacillus mojavensis_AG3. The adherence test revealed that Lysinibacillus cresolivorans_W2 (MK411028) recorded the highest adhesion property (60%). Oligo- and polysaccharides were synthesized by the action of dextransucrase enzyme and their cytotoxicity tests were negative. Dextran with a molecular weight (117521 Da) recorded the highest antimicrobial efficacy against Bacillus subtilis_AG1 and Bacillusmojavensis_AG3 (65%, 63.5%) respectively. The results concluded that the dextran was the most important factor causing the dental plaque pathogenicity. Also, oral oligo- and polysaccharides might play a role in dental plaque control.
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http://dx.doi.org/10.1016/j.micpath.2019.103626DOI Listing
October 2019

Biodegradation of feather waste by keratinase produced from newly isolated ALW1.

J Genet Eng Biotechnol 2018 Dec 28;16(2):311-318. Epub 2018 May 28.

Department of Chemistry of Natural and Microbial Products, Division of Pharmaceutical and Drug Industries Research, National Research Centre, Giza, Egypt.

Keratinase are proteolytic enzymes which have gained much attention to convert keratinous wastes that cause huge environmental pollution problems. Ten microbial isolates were screened for their keratinase production. The most potent isolate produce 25.2 U/ml under static condition and was primarily identified by partial 16s rRNA gene sequence as ALW1. Optimization studies for the fermentation conditions increased the keratinase biosynthesis to 72.2 U/ml (2.9-fold). The crude extracellular keratinase was optimally active at pH 8.0 and temperature 65 °C with 0.7% soluble keratin as substrate. The produced ALW1 keratinase exhibited a good stability over pH range from 7 to 9 and over a temperature range 50-60 °C for almost 90 min. The crude enzyme solution was able to degrade native feather up to 63% in redox free system.
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http://dx.doi.org/10.1016/j.jgeb.2018.05.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353909PMC
December 2018

Effect of Partial Substitution of Ration's Soybean Meal by Biologically Treated Feathers on Rumen Fermentation Characteristics (in vitro).

Pak J Biol Sci 2018;21(3):110-118

Background And Objective: Feather wastes are the most abundant keratinous material in the nature and its accumulation causes multiple environmental problems. Nutritive value upgrading of such wastes through biological treatments may provide ruminant's rations with high quality and cost effective source of protein. Therefore, the main objective of this study was to investigate the potential uses of biologically treated feathers (BTF) as a feedstuff for ruminants through in vitro experiments.

Materials And Methods: Keratinase production time course was performed by ten microbial isolates (3 fungal, 3 actinomyces and 4 bacterial isolates) under static and shaking conditions using turkey feather- synthetic medium. The chemical composition and amino acid analysis for the crude feathers, BTF and soybean meal were determined according to AOAC methods. Two in vitro experiments were conducted to study the effects of crude feathers, BTF and modified ruminant rations (in which soybean meal were substituted by the BTF in 10, 20 and 30%) on rumen fermentation characteristics. Ration's Dry Matter (DM), Organic Matter (OM), Neutral detergent fibre (NDF) and Acid detergent Fibre (ADF) degradability by rumen microorganisms were tested using batch culture technique. Ruminal final pH, ammonia-nitrogen, total volatile fatty acids and short chain fatty acids concentrations were determined after 24 h of incubation. The total gas production volume was determined using 100 mL glass syringes.

Results: Bacillus licheniformis ALW1 was the most potent keratinase producer strain under static condition at 37°C for four days of incubation. Feather biological treatment by Bacillus licheniformis increased its content of some of essential-sulphur amino acids. The degradability of BTF by rumen microorganisms was 4 folds higher than crude feather degradability. There were no significant differences between control and partially substituted (R10 and R20) rations in all of rumen fermentation characteristics.

Conclusion: The utilization of BTF as substitute for costly soybean meal in ruminant's rations up to 20% had no negative effect on all rumen fermentation characteristics.
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http://dx.doi.org/10.3923/pjbs.2018.110.118DOI Listing
August 2019

A synbiotic multiparticulate microcapsule for enhancing inulin intestinal release and Bifidobacterium gastro-intestinal survivability.

Carbohydr Polym 2018 Aug 20;193:137-143. Epub 2018 Mar 20.

Dairy Science Department, National Research Centre, Dokki, Cairo, Egypt. Electronic address:

A novel synbiotic multiparticulate microparticle was produced in the current study to expand the synbiotic industrial applications. Initially, the inulin was fabricated into PLGA nanoparticles. After the inulin entrapment efficiency was boosted to reach 92.9 ± 8.4% by adjusting the formulation parameters, the developed particles were characterized by different techniques such as particle size analyzer, TEM, and TLC. The obtained data showed that the particle size was 115.8 ± 82.7 nm, the particles had smooth surface and round shape, and the fabrication procedure did not affect the integrity of the inulin. Later, the inulin loaded nanoparticles together with selected Bifidobacterium species were double coated with gum arabic and alginate. The maximum survivability of the encapsulated Bifidobacterium in the simulated gastric solution reached 88.29% of the initial population, which was significantly higher than the survivability of the free bacteria. Finally, the inulin release from the multiparticulate microparticles was studied and found to be sustained over three days.
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http://dx.doi.org/10.1016/j.carbpol.2018.03.068DOI Listing
August 2018

Purification and characterization of a new thermophilic collagenase from Nocardiopsis dassonvillei NRC2aza and its application in wound healing.

Int J Biol Macromol 2018 Sep 8;116:801-810. Epub 2018 May 8.

Chemistry of natural and microbial products, National Research Centre, Dokki, Cairo, Egypt. Electronic address:

A thermostable metallo-collagenase enzyme (150 kDa), recently identified in a newly isolated actinomycestes strain (Nocardiopsis dassonvillei NRC2aza), has been purified from natural source, characterized to have application in wound healing. A simple 3 step purification procedure gave an increase of purity by 6.23 fold with a specific activity of 387.2 U mg. The enzyme activity showed stability across a range of pH (7.0-8.5) and temperature (40-55 °C) with optima at pH 8.0 and 60 °C, respectively. Activators include Mg, Ca, Zn, Na, K and Ba, while Mn, Co, Niand Ag ions gave partial inhibition. Full inhibition was given by other tested ions and metalloproteinase inhibitors. Broad substrate specificity was demonstrated including activity against a native collagen. The K and V of the enzyme using azocollagen were 5.5 mg/ml and 1280 U, respectively. The purified collagenase enhanced wound closure in vitro and in vivo and the repair process was dose dependent. Topical application of the purified collagenase (either of 25 or 50 U) to cutaneous wounds significantly accelerated the rate of wound healing and the formation of granulation tissue. Hence, the purified collagenase has a great potential as a therapeutic agent in wound care and collagen related diseases.
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http://dx.doi.org/10.1016/j.ijbiomac.2018.05.030DOI Listing
September 2018

A novel variant in ATM gene causes ataxia telangiectasia revealed by whole-exome sequencing.

Neurosciences (Riyadh) 2018 Apr;23(2):162-164

Department of Pediatrics, Prince Sultan Military Medical City, Riyadh, Kingdom of Saudi Arabia. E-mail:

Ataxia-Telangiectasia (A-T) is an autosomal recessive disorder caused by variants in ATM gene and characterized by progressive neurologic impairment, cerebellar ataxia, and oculo-cutaneous telangiectasia. Immunodeficiency with a recurrent sinopulmonary infections are observed in patients with A-T. Here, we report a novel stop codon variant, c.5944 C>T (p.Gln1982*), revealed by whole-exome sequencing in a 9-year old boy. He presented with recurrent upper respiratory tract infections, failure to thrive, developmental delay, ataxic gait, and bulbar telangiectasia.
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http://dx.doi.org/10.17712/nsj.2018.2.20170463DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8015445PMC
April 2018

Enzymatic synthesis using immobilized Enterococcus faecalis Esawy dextransucrase and some applied studies.

Int J Biol Macromol 2016 Nov 17;92:56-62. Epub 2016 Jun 17.

Department of Chemistry of Microbial and Natural Products, National Research Centre (NRC), Dokki, Cairo, Egypt. Electronic address:

Dextrans enzymatic synthesis by immobilized Enterococcus faecalis Esawy dextransucrase was studied. Different parameters, such as: enzyme protein concentration (EPC), substrate concentration (SC), temperature and reaction time were evaluated. EPC played a fundamental role in controlling dextran molecular size with 0.1% dextran in reaction mixture. Dextran 38,397 and 125,471Da were yielded at EPC 4.78 and 5.78mg, respectively. Proper dextrans (73,378 and 117,521Da) demanded in pharmaceutical applications were achieved at 6% and 12% sucrose concentrations and at 4.78 and 5.78mg EPC, respectively. Optimum temperature for conversion of glucose to dextran was 30°C (73% and 80% at 5.78 and 4.78mg EPC, respectively). Varieties of maltooligosaccharides (MOS) were yielded by synergistic cooperation between sucrose and maltose. Six MOS and three dextrans samples in vitro have prebiotic effect on Lactobacillus casei with degree of variation. Two samples of MOS with different degree of polymerization (DP) and three samples of dextran with different molecular weight (MW) reported different fibrinolytic activity.
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http://dx.doi.org/10.1016/j.ijbiomac.2016.06.041DOI Listing
November 2016

Patterns of folic acid use in pregnant Saudi women and prevalence of neural tube defects - Results from a nested case-control study.

Prev Med Rep 2015 26;2:572-6. Epub 2015 Jun 26.

Prince Sultan Military Medical City, Riyadh, Kingdom of Saudi Arabia.

Background: Although the role of folic acid (FA) in preventing neural tube defects (NTDs) is well documented, its optimal intake in pregnant women is still low in many countries. Here, we prospectively studied the prevalence of NTDs in the newborns and the patterns of FA intake in pregnant Saudi mothers.

Methods: This case-control study was nested within a 3-year project (July 2010 to June 2013) to study the patterns of birth defects in the offspring of Saudi women who received their antenatal care and delivered at Prince Sultan Military Medical City, Riyadh-Saudi Arabia. Enrolled mothers were divided into 4 groups: group 1 (FA taken before pregnancy and continued regularly after conception), group 2 (FA taken post-conception), group 3 (no FA intake), and group 4 (did not remember or were unsure of taking FA). Control mothers were randomly selected from those with normal first obstetrical ultrasound scan at 18-22 weeks of gestation.

Results: The cohort included 30,531 mothers giving birth to 28,646 infants. We studied 1179 mothers of babies with birth defects (BDs) and 1262 control mothers. There were 237 (9.7%) mothers in-group 1; 2001 (82%) in-group 2; 154 (6.3%) in-group 3; and 49 (2%) in-group 4. There were 49 babies with NTDs, a prevalence of 1.7/1000 total births. Among the studied mothers 2274 (93%) took FA either full or partial course.

Conclusion: The high prevalence of NTDs and the low optimal FA intake highlight the need for a strict implementation of staple food fortification and health education program for Saudi women.
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http://dx.doi.org/10.1016/j.pmedr.2015.06.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4721389PMC
February 2016

Covalent immobilization of Enterococcus faecalis Esawy dextransucrase and dextran synthesis.

Int J Biol Macromol 2016 Jan 3;82:905-12. Epub 2015 Oct 3.

Department of Chemistry of Microbial and Natural Products, National Research Centre (NRC), Dokki, Cairo, Egypt. Electronic address:

Enterococcus faecalis Esawy dextransucrase was immobilized in Fe(3+)-cross-linked alginate/carboxymethyl cellulose (AC) beads. The gel beads were modified with polyethylenimine (PEI) followed by glutaraldehyde (GA) to form Fe(3+) (ACPG) beads. Fe(3+) (ACPG) was characterized using FTIR and DSC techniques. GA activated beads showed new two peaks. The first was at 1,717 cm(-1) which refers to (CO) group of a free aldehyde end of glutaraldehyde, and another peak was at 1,660 cm(-1) referring to (CN) group. The immobilization process improved the optimum temperature from 35 to 45°C. The immobilized enzyme showed its optimum activity in wide pH range (4.5-5.4) compared to pH 5.4 in case of free form. Also, the immobilization process improved the thermal and pH enzyme stability to great extent. Reusability test proved that the enzyme activity retained 60% after 15 batch reactions. Immobilized enzyme was applied successfully in the synthesis of oligosaccharides and different molecular weights of dextran.
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http://dx.doi.org/10.1016/j.ijbiomac.2015.09.076DOI Listing
January 2016

Multiplexed integrating plasmids for engineering of the erythromycin gene cluster for expression in Streptomyces spp. and combinatorial biosynthesis.

Appl Environ Microbiol 2015 Dec 2;81(24):8402-13. Epub 2015 Oct 2.

Department of Biology, University of York, York, United Kingdom

Bacteria in the genus Streptomyces and its close relatives are prolific producers of secondary metabolites with antibiotic activity. Genome sequencing of these bacteria has revealed a rich source of potentially new antibiotic pathways, whose products have never been observed. Moreover, these new pathways can provide novel genes that could be used in combinatorial biosynthesis approaches to generate unnatural analogues of existing antibiotics. We explore here the use of multiple orthologous integrating plasmid systems, based on the int/attP loci from phages TG1, SV1, and ϕBT1, to express the polyketide synthase (PKS) for erythromycin in a heterologous Streptomyces host. Streptomyces strains containing the three polyketide synthase genes eryAI, eryAII, and eryAIII expressed from three different integrated plasmids produced the aglycone intermediate, 6-deoxyerythronolide B (6-dEB). A further pair of integrating plasmids, both derived from the ϕC31 int/attP locus, were constructed carrying a gene cassette for glycosylation of the aglycone intermediates, with or without the tailoring gene, eryF, required for the synthesis of erythronolide B (EB). Liquid chromatography-mass spectrometry of the metabolites indicated the production of angolosaminyl-6-dEB and angolosaminyl-EB. The advantages of using multiplexed integrating plasmids for engineering expression and for combinatorial biosynthesis were demonstrated.
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http://dx.doi.org/10.1128/AEM.02403-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4644662PMC
December 2015

The effect of water quality on the immunoreactivity of stress-response cells and gonadotropin-secreting cells in the pituitary gland of Nile tilapia, Oreochromis niloticus.

J Exp Zool A Ecol Genet Physiol 2015 Mar 11;323(3):146-59. Epub 2015 Feb 11.

Fish Reproduction Laboratory, National Institute of Oceanography and Fisheries, Cairo, Egypt.

The present experiments investigated the effect of water quality characteristics on the condition factor, the ovarian activity, cortisol level, and the immunoreactivity of stress-response cells (adrenocorticotropic hormone; ACTH- and melanin stimulating hormone; MSH- and somatolactin; SL- secreting cells) and gonadotropin (GTH)-secreting cells in the pituitary gland of Nile tilapia, Oreochromis niloticus. After 3 months of exposure to mixtures of water from different sources (Tap and Lake Manzalah waters), with high levels of minerals and heavy metals, water quality affected the number, size, and immunostaining of stress-response-immunoreactive (ir) cells and GTH-ir cells, which showed a dramatic decrease in their size. The integrated optical density (IOD) of immunoreactivity of MSH- and GTH- cells was significantly increased; however, it was significantly decreased for ACTH- and SL- cells. Also, high levels of cortisol were observed in females exposed to waters with high concentrations of minerals and heavy metals. In parallel, low values of gonadosomatic index (GSI%) and the ovarian histology revealed a decrease of maturing follicles concomitant with an increase of atretic follicles in females exposed to Lake Manzalah polluted water. Taken together, the increased activity of stress-response-ir pituitary cells, serum cortisol level and ovarian atretic follicles in response to elevated concentrations of minerals and heavy metals, supports the possible role of ACTH, MSH, and SL in the adaptive stress response of fish. Therefore, minerals and heavy metals must be considered when discussing tilapia aquaculture status.
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http://dx.doi.org/10.1002/jez.1901DOI Listing
March 2015

Levansucrase optimization using solid state fermentation and levan biological activities studies.

Carbohydr Polym 2013 Jul 2;96(1):332-41. Epub 2013 Apr 2.

Department of Chemistry of Natural and Microbial Products, National Research Centre, Dokki, Giza, Egypt.

Bacillus subtilis NRC1aza produced levansucrase under solid state fermentation using starch as support. A sequential optimization strategy, based on statistical experimental designs is employed to enhance enzyme productivity. First, a 2-level Plackett-Burman design was applied for bioprocess parameters screen that significantly increase levansucrase production. Second optimization step was performed using fractional factorial design in order to optimize the amounts of highest positive variables that had significant effect on levansucrase productivity. Maximal enzyme productivity of 170 U/gds was achieved in presence of glucose, yeast extract, and pH 8. In vitro, experiments confirmed that LevCR and LevQT had an antitumor activity against different animal and human cancer cell lines by demonstrating inhibitory effects on growth of Ehrlich ascites carcinoma cell line, human MCF-7 breast and liver HepG2 cancer cell lines, in particular LevQT was found to be efficacious compared to anticancer drug, cisplatin. Result focused in LevCR as strong fibrinolytic agent.
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http://dx.doi.org/10.1016/j.carbpol.2013.03.089DOI Listing
July 2013

Effect of stress during handling, seawater acclimation, confinement, and induced spawning on plasma ion levels and somatolactin-expressing cells in mature female Liza ramada.

J Exp Zool A Ecol Genet Physiol 2012 Aug 24;317(7):410-24. Epub 2012 May 24.

Fish Reproduction Laboratory, National Institute of Oceanography and Fisheries, Alexandria, Egypt.

The present experiments were designed to determine the effect of different stress factors; handling, seawater acclimation, confinement, and induced spawning on plasma cortisol, hydro mineral balance as well as changes in size, number and integrated intensity of somatolactin (SL)-expressing cells in Liza ramada mature females confined to fresh water ponds. The plasma levels of cortisol, PO(4)(3-), Na(+), and K(+) were higher, while Ca(2+) and Mg(2+) were lower than controls during transportation without anesthesia. By using clove oil (5 mg L(-1)) as an anesthetic during transportation, the plasma cortisol, PO(4) (3-), Na(+), and K(+) were similar to controls, while Ca(2+) and Mg(2+) were higher. During seawater acclimation, the plasma cortisol and minerals were significantly higher except Na(+) which was lower than controls. In addition, during induction of spawning, the plasma levels of cortisol, PO(4)(3-), Na(+), K(+), and Mg(2+) were significantly higher than controls. The SL-producing cells are located in the pars intermedia (PI) bordering the neurohypophysis. The stress affected the number, size, and immunostaining of SL-expressing cells. During seawater acclimation, the size and the integrated intensity of SL immunoreactivity were lower, but the number of these cells was higher than controls. Furthermore, the number, size, and the integrated intensity of SL immunoreactivity were significantly lower than controls during handling and after spawning, which was opposite to confinement. The response of SL-expressing cells in PI in parallel with changes in cortisol and hydro mineral balance induced by stress support the possible role of SL in the adaptive response of fish to stress.
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http://dx.doi.org/10.1002/jez.1734DOI Listing
August 2012
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