Co-biodegradation of pyrene and other PAHs by the bacterium Acinetobacter johnsonii

Polycyclic aromatic hydrocarbons (PAHs) usually co-exist in environment with interactional effects. Currently, Acinetobacter johnsonii was employed to degrade 400 mg L^-1 of pyrene (PYR) and kinetic modeling indicated substrate inhibition over 76 mg L^-1 by introducing an inhibition constant parameter. In PAHs co-biodegradation, naphthalene (NAP) dominated biodegradation processes through the preferential utilization as growth substrate. The peak biodegradation of PYR increased to 415 mg L^-1 with 65 mg L^-1 of NAP. Furthermore, phenanthrene (PHE), PYR and anthracene (ANT) were degraded in turn and ended in reverse order. When the concentrations reached their respective limiting concentration of 22%, ANT could not be degraded and PHE and PYR biodegradations also respectively terminated at 66 and 45 h later with a removal rate of 40% and 26% due to very low specific activities of salicylate hydroxylase and catechol 2,3-dioxygenase. However, by introducing 125-133 mg L^-1 of NAP, the bacterial potential was effectively enhanced to 29% after cell underwent a re-stimulation stage with the exhaustion of NAP. NAP prominently contributed to cell growth to stimulate secretion of key enzymes, but the advantage would gradually get lost with the decline of its titer. To research the interplay of PAHs is conducive to targeted decontamination.