Biodegradation Mechanism of Anionic Polyacrylamide in Coal Preparation Using Molecular Simulation

Abstract

Biodegradation of anionic polyacrylamide (HPAM) and polyacrylate (PAA) by key enzymes, such as amidase and bacterial laccase, have been reported. However, the interaction mechanism between HPAM or PAA and enzymes is still poorly unclear. Here, docking study was undertook to demonstrate the binding modes and interaction details for degradation of HPAM or PAA. Then, bioactivities between PAA and HPAM were compared with frontier orbital theory. The docking results showed that HPAM completely buried in pocket of Rhodococcus sp. N-771 amidase (Rh Amidase), while most of PAA molecule exposed outside pocket of Bacillus subtilis laccase ( B. subtilis laccase ), further suggesting PAA was much more difficult to degrade than HPAM. Hydrophobic interactions and hydrogen bonds were necessary for stabilizing HPAM-Rh Amidase or PAA- B. subtilis laccase complex. The frontier orbital analysis indicated that bioactivity of PAA was higher than that of PAA. These findings provide an insight into enzyme-catalyzed degradation of HPAM. It is helpful in designing highly efficient enzymes against HPAM or PAA to protect environment.