P26: Increasing of soil binding ability of organophosphorus hydrolase enzyme by the increase of iso-electric point

The experiment was conducted to observe the binding ability of organophosphorus hydrolase enzyme (OphB) which is capable of degrading organophosphorus pesticides with soil particles and the factors which are related to the binding ability were also studied. Immobilization of OphB with soil particles was observed by confocal microscopy, and Atomic force microscopy (AFM), it was also observed that OphB enzyme was capable to bind with different types of soil particles. Moreover, clay soil was suitable for binding of OphB enzyme and particular amount of OphB enzyme (1 mg/ml) was enabled to bind with particular amount of soil particles (60 mg/ml montmorillonite soil). Besides, maximum binding of OphB enzyme with montmorillonite soil was observed at pH 7.  On the other hand, mutation of OphB enzyme was conducted to increase the adhesion force or binding force of OphB enzyme by increasing iso-electric point (pI) of OphB enzyme. Estimated iso-electric point was increase from 8.69 for OphB wild type to 9.16 for triple mutant. Similarly, binding ability was increased 16.80% for triple mutant followed by 11.50% for double mutant and 5.30% for single mutant than that of OphB wild type enzyme. Besides, adhesion forces were gradually increased from OphB wild type enzyme (90 pN) to triple mutant OphB enzyme (104 pN). There was an increasing trend of adhesion force by the increase of pI or positive charge of OphB enzyme. So pI of OphB enzyme is supposed to important factor for binding with soil particles.