Aerobic degradation of polynitro explosives by Rhodococcus opacus JW01 and JW02

This research details the identification and degradation characteristics of bacteria that can utilize recalcitrant and environmentally ubiquitous explosives. The objectives of the research were (1) examine the potential for 2,4,6-trinitrophenol (TNP) mineralization by bacteria isolated from TNP contaminated soil, (2) develop a bioreactor for degradation of TNP and (3) examine the ability of these TNP degraders to utilize other explosives.; Two TNP-degrading Rhodococcus opacus strains, JW01 and JW02, were isolated from Mare Island Naval Shipyard soil, Vallejo, CA, contaminated with TNP. After isolation and identification of the strains, growth and TNP degradation characteristics of the isolates were examined in batch culture studies. The bacteria were found to utilize TNP as the sole carbon and nitrogen source in the concentration range 0.5 to 1100 mg/l. Mineralization of TNP was proven with the production of 14CO2 from 14C-TNP [ring-UL]. The R. opacus strain JW01 was found to have a yield coefficient of 0.16 g cells-N/g TNP-N. The Edwards model provided the best fit to the data and the inhibited growth parameters mu max, KS, and KI were 0.58 h-1, 25 mg/l and 112 mg/l, respectively.; A sequencing batch reactor was designed for TNP degradation and seeded with R. opacus JW01, but was not kept sterile during the experiments. The TNP removal efficiency was 99.9% resulting in an effluent TNP concentration consistently below the 57 mug/l drinking water standard. Monod growth and degradation parameters were obtained by a least squares fit to the experimental data. Values of mumax and Ks were estimated to be 0.134, 0.68; 0.079, 1.11; and 0.044, 1.24 (units d -1, mg/l) for 25, 15 and 10°C cycles respectively.; The ability of the isolates to degrade other explosives alone and in the presence of TNP was examined using batch reactor studies. It was found that the TNP-degraders could degrade 2,4-dinitrophenol (DNP) as the sole carbon and nitrogen source up to 100 mg/l and utilize TNB up to 12 mg/l when TNB was the sole nitrogen source available. Additionally, the results show that the isolates are able to cometabolize 2,4,6-trinitrotoluene, RDX, 4-nitrophenol, and 2,4- and 2,6-dinitrotoluene to some extent.