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Articles by Yasser R. Abdel-Fattah
Total Records ( 5 ) for Yasser R. Abdel-Fattah
  Mahmoud M. Berekaa , Yasser R. Abdel-Fattah and Hany M. Hussein
  An experimental design technique was carried out to investigate the bioaccumulation of chromium VI by the rubber degrading nocardioform actinomycete Gordonia polyisoprenivorans VH2. Response Surface Methodology (RSM) was adopted to acquire the best level of four variables namely, pH, FeSO4, NaNO2 and Cr (VI) which have been optimized to bring about maximum chromium biosorption percentage. In this respect, the 3-level Box-Behnken design was employed. A polynomial model has been created to correlate the relationship between the four variables and chromium biosorption. The optimal combination of those variables for chromium biosorption evaluated from the non-linear optimization algorithm of EXCEL-Solver was as follows (mg L-1): FeSO4, 18; NaNO2, .75; Cr (VI), 41.25 at pH 6.7. Based on the predicted model, an experimental verification of the optimal conditions revealed chromium biosorption percentage of 90%, which is more than 3 folds the basal medium.
  Mahmoud M. Berekaa , Nadia A. Soliman and Yasser R. Abdel-Fattah
  In a molecular screening program to select a potent thermostable amylase from a previously isolated thermophiles, a locally isolated, thermophilic lipase-producing Geobacillus thermoleovorans YN (accession number AF385083), was shown to secrete a thermostable α-amylase constitutively. The optimal enzyme activity was measured at 75°C, where 90% of the activity was retained at 80°C after one hour of incubation. A catabolite repression due to the addition of glucose to the basal salt medium was demonstrated, while 4 folds increase in volumetric production was achieved in LB and starch-supplemented basal salt media and presented in SDS-PAGE and zymogram. A blunt end PCR fragment (2146 bp) was amplified from genomic DNA using a designed set of primers and ligated to Bluescript —II KS(+) vector, transformed to E. coli DH5-α competent cells by electroporation and screened on LB-agar plates induced with IPTG. Nucleotide sequencing of selected clone revealed two ORFs, the first was (GTG) with a molecular size 1649 nucleotides encoding 549aa residues of a predicted molecular weight 62.592 kD and the second (ATG) with a molecular size 1613 nucleotides encoding 537aa residues of a predicted molecular weight 61.04 kD.
  Mahmoud M. Berekaa , Yasser R. Abdel-Fattah , Samia M. El-Sayed , Aliaa M. EL Borai and Samy A. El Aassar
  An optimization study of biopolymer production by locally isolated Bacillus sp. strain-R was carried out, where analysis indicated that it is a polyamide homopolymer consists mainly of glutamate. Preliminary experiment to address the most suitable carbon and nitrogen sources revealed that a production of 14.25 g L-1 of the polyamide (polyglutamate) was achieved in the presence of glucose and ammonium sulfate. To evaluate the effect of different culture conditions on the production of PGA, Plackett-Burman factorial design was carried out. Ten variables were examined for their significance on PGA production. Among those variables K2HPO4, KH2PO4, (NH4)2SO4 and glucose were found to be the most significant variables that encourage PGA production. The pre-optimized medium showed approximately three folds increase in PGA production.
  Yasser R. Abdel-Fattah , Ehab R. El-Helow , Khaled M. Ghanem and Walid A. Lotfy
  Statistically based experimental designs were applied to optimize the production of avicelase by a recently isolated endospore forming strain, WL1, that showed 99.8% 16S rDNA identity to Geobacillus stearothermophilus. Seven culture parameters were examined for their significance as effectors of avicelase expression using the Plackett-Burman factorial design. Concentrations of avicel, yeast extract and ammonium sulfate were the most significant factors affecting the process of enzyme production. The second optimization step was to figure out the levels of these three independent variables that generate maximum avicelase activity, using the Box-Behnken design. Maximal enzyme activity (0.8 U mL-1), which is approximately two folds the activity expressed in the basal medium, has been predicted at concentrations of (g L-1): Avicel (42), yeast extract (3.6) and ammonium sulfate (0.8). A verification experiment was accomplished and revealed approximately 99% model validity.
  Yasser R. Abdel-Fattah
  Twelve and fourteen membered ring macrolides produced by Streptomyces venezuelae are characterized by their effectiveness on respiratory pathogens in comparison with erythromycin antibiotic. In the present study, the effect of culture conditions on the production of three macrolides of this family, namely: Pikromycin, methymycin and neomethymycin were evaluated. Plackett-Burman experimental design based on numerical modeling was implemented in 20 trials matrix to design a pre-optimized media for the three antibiotics using some pharama grade components in comparison with SCM medium. Among the examined culture conditions, sodium nitrate and unrefined hydrolyzed soy protein were found stimulating the production of all three macrolides. In addition, inoculum size and soluble starch showed significant increase of pikromycin production, while xylose improved production of methymycin. In all studied macrolides, higher temperature inhibited their accumulation in fermentation broth. The pre-optimized medium, based on statistical analysis, showed a production of 123 mg L-1 pikromycin, which is more than two times the basal SCM medium.
 
 
 
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