Effect of HP-β-CD on the biodegradation of nitrobenzene at high concentration by Acinetobacter sp.

The present study investigated the effect of Hydroxypropylβcyclodextrin (HPβCD) on the cell growth, removal of nitrobenzene and the transformation of intermediates during the biodegradation process of nitrobenzene at high concentration by Acinetobacter sp. 2aminophenol was identified as an intermediates using direct acetylation of biodegraded samples of nitrobenzene by acetic anhydride followed by GCMS analysis. When the initial concentration of nitrobenzene was about 400?mg·L-1 (optimal concentration for degrading bacteria to grow vigorously), HPβCD added at 250?mg·L-1 or 500?mg·L-1 had no effect on the biomass and the degradation of nitrobenzene. However, the addition of HPβCD at above 2000?mg·L-1, significantly enhanced the cell growth, the biodegradation of nitrobenzene and the transformation of intermediates when the initial concentration of nitrobenzene was about 850?mg·L-1. The promoting effect was increased proportionally with the dosage of HPβCD, which was mainly due to the detoxification ability of HPβCD through the formation inclusion complexes with nitrobenzene and 2aminophenol. The biodegradation kinetics of 850?mg·L-1 nitrobenzene followed firstorder reaction when HPβCD was added at 0, 2000, 4000?mg·L-1, and the kinetic constant was increased from 00077?h-1 to 00089 and 00161?h-1. However, when HPβCD was added at 8000?mg·L-1, the kinetics was changed to zeroorder reaction and the kinetic constant was 161162?mg·L-1·h-1. 