Effect of pulsed electric fields (PEF) on protease and antioxidant activity of selenium modified fibrinolytic enzyme nattokinase produced by Bacillus natto cells

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Effect of pulsed electric fields (PEF) on protease and antioxidant activity of selenium modified fibrinolytic enzyme nattokinase produced by Bacillus natto cells

Khalid Amin, Xiangbo Zeng, You Ying, Yang Hu, Sun He, Lv Bo, Naveed Ahmad, Muhammad Ishaq, Hansong Yu
Int. J. Biosci.14( 5), 282-293, May 2019.
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Nattokinase is a serine protease of the subtilisin family which exhibits a strong fibrinolytic activity and works by inactivating plasminogen activator inhibitor 1 (PAI-1). In this study selenium was enriched in nattokinase, as it has many functions incorporated with selenoprotein like as an antioxidant which protects the body from oxidative stress. Also, effect of pulsed electric field (PEF) on protease and antioxidant activity of selenium enriched nattokinase was determined. SDS-PAGE was used to determine the molecular weight and purity of enzyme. Antioxidant activity was evaluated by different spectrophotometric methods like, DPPH, OH radical scavenging, FRAP and T-AOC assay. Optimization of PEF parameters revealed that 2 kV/cm of electric field strength,   10 min electroporation time, 20 µs of pulse width and 1 Hz frequency were suitable conditions for cell vitality and nattokinase production. The vitality of selenium enriched cells was higher most (9.34 × 107) at optimized PEF treatment. After PEF treatment, the overall antioxidant activity was significantly (P < 0.05) increased. However the DPPH activity increased from 0.38±0.03 mg/mL (NK1) to 0.107±0.01 mg/mL (NK4) of EC50 values. The improvement of ·OH radical scavenging activity was observed from 60.63±5.2 U/mg (NK1) to 104.8±5.6 U/mg (NK4). The antioxidant activity by T-AOC and FRAP assays after PEF treatment was improved from 32.8±4.0 U/mg and 682.63±70.6 µg TE/mg (NK1) to 63.3±3.5 U/mg and 844.46±81.05 µg TE/mg respectively. From this study, it was concluded that selenium enrichment by pulsed electric field can analogously enhance the antioxidant and protease activity of novel fibrinolytic enzyme nattokinase.


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