Purification and Biochemical Characterization of a Detergent Stable α-amylase from Pseudomonas stutzeri AS22

Hana Maalej,Noomen Hmidet,Olfa Ghorbel-Bellaaj,Moncef Nasri 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.5

This study reports the purification and biochemical characterization of a novel maltotetraose-forming-α-amylase from Pseudomonas stutzeri AS22, designated PSA. The P. stutzeri α-amylase (PSA) was purified from the culture supernatant to homogeneity by Sepharose mono Q anion exchange chromatography, ultrafiltration and Sephadex G-100 gel filtration, with a 37.32-fold increase in specific activity, and 31% recovery. PSA showed a molecular weight of approximately 57 kDa by SDS-PAGE. The N-terminal amino acid sequence of the first 7 amino acids was DQAGKSP. This enzyme exhibited maximum activity at pH 8.0 and 55oC, performed stably over a broad range of pH 5.0 ~ 12.0, but rapidly lost activity above 50oC. Both potato starch and Ca2+ ions have a protective effect on the thermal stability of PSA. The enzyme activity was inhibited by Hg2+, Mn2+, Cd2+, Cu2+, and Co2+, and enhanced by Ba2+. PSA belonged to the EDTA-sensitive α-amylase. The purified enzyme showed high stability towards surfactants (Tween 20, Tween 80 and Triton X-100), and oxidizing agents, such as sodium per borate and H2O2. In addition, PSA showed excellent compatibility with a wide range of commercial solid and liquid detergents at 30oC, suggesting potential application in the detergent industry. Maltotetraose was the specific end product obtained after hydrolysis of starch by the enzyme for an extended period of time, and was not further degraded.

Laboratory Simulation of Corrosion Damage in Reinforced Concrete

Altoubat, S.,Maalej, M.,Shaikh, F.U.A. Korea Concrete Institute 2016 International Journal of Concrete Structures and M Vol.10 No.3

This paper reports the results of an experimental program involving several small-scale columns which were constructed to simulate corrosion damage in the field using two accelerated corrosion techniques namely, constant voltage and constant current. A total of six columns were cast for this experiment. For one pair of regular RC columns, corrosion was accelerated using constant voltage and for another pair, corrosion was accelerated using constant current. The remaining pair of regular RC columns was used as control. In the experiment, all the columns were subjected to cyclic wetting and drying using sodium chloride (NaCl) solution. The currents were monitored on an hourly interval and cracks were visually checked throughout the test program. After the specimens had suffered sufficient percentage steel loss, all the columns including the control were tested to failure in compression. The test results generated show that accelerated corrosion using impressed constant current produces more corrosion damage than that using constant voltage. The results suggest that the constant current approach can be better used to simulate corrosion damage of reinforced concrete structures and to assess the effectiveness of various materials, repair strategies and admixtures to resist corrosion damage.

Laboratory Simulation of Corrosion Damage in Reinforced Concrete

S. Altoubat,M. Maalej,F. U. A. Shaikh 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.3

This paper reports the results of an experimental program involving several small-scale columns which were constructed to simulate corrosion damage in the field using two accelerated corrosion techniques namely, constant voltage and constant current. A total of six columns were cast for this experiment. For one pair of regular RC columns, corrosion was accelerated using constant voltage and for another pair, corrosion was accelerated using constant current. The remaining pair of regular RC columns was used as control. In the experiment, all the columns were subjected to cyclic wetting and drying using sodium chloride (NaCl) solution. The currents were monitored on an hourly interval and cracks were visually checked throughout the test program. After the specimens had suffered sufficient percentage steel loss, all the columns including the control were tested to failure in compression. The test results generated show that accelerated corrosion using impressed constant current produces more corrosion damage than that using constant voltage. The results suggest that the constant current approach can be better used to simulate corrosion damage of reinforced concrete structures and to assess the effectiveness of various materials, repair strategies and admixtures to resist corrosion damage.

Situation of HPV16 E2 Gene Status During Radiotherapy Treatment of Cervical Carcinoma

Kahla, Saloua,Kochbati, Lotfi,Maalej, Mongi,Oueslati, Ridha Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.6

Background: Human papillomavirus (HPV) integration within the E2 gene has been proposed as a critical event in cervical carcinogenesis. This study concerned whether HPV16 status and E2 gene intactness are predictive of radiation response in patients with cervical cancer. Materials and Methods: Biopsies of 44 patients with cervical cancer were collected before or after radiotherapy. The presence of HPV16 was assessed by polymerase chain reaction (PCR) using specific primers for the L1 region. E2 disruption was detected by amplifying the entire E2 gene. Results: HPV16 DNA was found in 54.5% of the clinical samples. Overall, 62.5% of the HPV16 positive tumors had integrated viral genome and 37.5% had episomal genome. There was a tendency of increase of HPV16 E2 negative tumors compared with HPV16 L1 ones in advanced stages (75% versus 20% in stage III respectively). Detection of E2 gene appeared influenced by the radiotherapy treatment, as the percentage of samples containing an intact HPV16 E2 was more frequent in pretreated patients compared to radiotherapy treated patients (66.6% versus 20%). The radiation therapy caused an eight-fold [OR= 8; CI=1.22-52.25; p=0.03] increase in the risk of HPV16 genome disruption. The integration status is influenced by the irradiation modalities, interestingly E2 disruption being found widely after radiotherapy treatment (75%) with a total fractioned dose of 50Gy. Conclusions: This study reveals that the status of the viral DNA may be used as a marker to optimize the radiation treatment.

Production and Biochemical Characterization of α-amylases from Bacillus mojavensis A21 Grown on Chicken Feathers Medium

Noomen Hmidet,Hana Maalej,Hanen Ben Ayed,Sofiane Ghorbel,Habib Kriaa,Moncef Nasri 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.4

Extracellular α-amylases produced by a newly isolated feather degrading bacterium strain Bacillus mojavensis A21 was optimized and characterized. Zymography showed that the A21 strain produced at least two α-amylases. Higher α-amylase production was achieved in the presence of 10 g/L chicken feathers and 1 g/L yeast extract. The growth of B. mojavensis A21 using chicken feathers as the nitrogen and carbon source resulted in its complete degradation after 48 h incubation at 37°C. However,maximum α-amylase activity was attained after 24 h. The optimum temperature and pH for crude α-amylase activity were 60°C and 6.5, respectively, and its activity was inhibited by EDTA. The end products of starch hydrolysis were maltose, maltotriose, and maltotetraose. α-Amylases from the A21 strain also catalyzed transglycosylation reactions when maltotetraose and maltopentaose were used as substrates and formed higher molecular weight maltoligosaccharides from G5 to G8. The maltooligosaccharide forming endo-α-amylases is useful in bread making as an anti-staling agent and can be produced economically using a low-cost medium with chicken feathers as the substrate.

Quantifying Raman and emission gain coefficients of Ho³⁺ doped TeO₂.ZnO.PbO.PbF₂.Na₂O (TZPPN) tellurite glass

Damak, K.,Yousef, E.S.,Al-Shihri, A.S.,Seo, H.J.,Russel, C.,Maalej, R. Elsevier 2014 SOLID STATE SCIENCES Vol.28 No.-

Broadband amplifier emission near the second telecommunication window in Ho<SUP>3+</SUP> doped 76TeO<SUB>2</SUB>.10ZnO.9.0PbO.1.0PbF<SUB>2</SUB>.3.0Na<SUB>2</SUB>O was studied. The optical transition properties and radiative lifetimes of several excited states of Ho<SUP>3+</SUP> have been predicted using intensity Judd-Ofelt parameters. The emission cross section for Ho<SUP>3+</SUP> in this glass, around 2 μm, was calculated according to McCumber theory. The maximum stimulated emission cross section was calculated to be 0.9 x 10<SUP>-20</SUP> cm<SUP>2</SUP> for 2046 nm emissions. The theoretical gain cross sections was evaluated and positive gain bands was anticipated. Furthermore, the peak Raman gain coefficient in the present glass was around 250 times larger than that of SiO<SUB>2</SUB>.