Sunday, August 10, 2008
P55

Adaptation of Rhodococcus rhodochrous  DAP 96622 to Acrylonitrile Degradation on a Trickling Bed Bioreactor

Jie Zhang and George E. Pierce. Department of Biology, Georgia State University, 24 Peachtree Center Ave, Atlanta, GA 30303

Acrylonitrile (AN) is a major volatile waste generated in the production of acrylamide and often associated with aromatic contaminants (toluene and styrene) in plant effluents.We examined Rhodococcus rhodochrous DAP 96622 to determine if it could be adapted to efficient biodegradation of AN in a bioreactor. A model bioreactor with granular activated carbon (GAC) as a substratum for Rhodococcus with AN as sole carbon or in combination with toluene(Tol) was established. Immobilized cells in the bioreactor, at starting concentrations of AN up to 1150 mg l-1 in the presence of Tol, had at least 13 fold higher AN degradation rates than that seen of planktonic cells. A near steady state of AN degradation was maintained at 75-85% for AN and 80%-90% for Tol within the parameter of EBRT=8 min and AN and Tol inlet loads between 50-200 mg l-1 h-1 and 200-500 mg l-1h-1, respectively. Biofilms with discrete microcolonies interspersed with voids and channels were observed using confocal scanning laser microscopy (CSLM). Precise measurement of biofilm characteristics agreed with the assumption that the biomass and biofilm thickness increased along the carbon column depth. With a porous attachment material like GAC, substrate diffusion is most likely not a limiting factor for AN degradation. Rhodococcus rhodochrous DAP 96622 in a non-sterile activated charcoal column showed efficient degradation of AN in the presence of Tol. The Rhodococcus bioreactor may provide a potential practical waste gas and water treatment system.  

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