Degradation pathways and kinetics of anthraquinone compounds along with nitrate removal by a newly isolated Rhodococcus pyridinivorans GF3 under aerobic conditions

A novel Rhodococcus pyridinivorans GF3 capable of degrading anthraquinone compounds (ACs) was isolated from 1-amino-4-bromoanthraquinone-2-sulfonic acid contaminated soil under aerobic conditions. Strain GF3 could degrade nine ACs at 150 rpm and 30 °C. LC-MS analysis showed that ACs were degraded via catechol and salicylic acid-produced pathways, which were different from previously reported phthalic acid-produced pathway. Strain GF3 could also completely remove ACs along with nitrate removal via aerobic denitrification. Further analysis found that the catechol as a metabolite of ACs could contribute to aerobic denitrification. The degradation of the mixture of five ACs used in 1-amino-4-bromoanthraquinone-2-sulfonic acid-producing process followed the modified Gompertz model under aerobic denitrification. During this process, except for anthraquinone (29.5% removal), the degradation efficiencies of hydrophilic and hydrophobic ACs reached over 90% and 60% in 48 h, respectively. These results show that strain GF3 is of potential application for the treatment of anthraquinone dye intermediates-containing wastewaters.