Evaluation of a creosote-based medium for the growth and preparation of a PAH-degrading bacterial community for bioaugmentation

Creosote was evaluated as an inexpensive carbon source for growing inocula of a polycyclic aromatic hydrocarbon (PAH)-degrading bacterial community (c ommunity five). Creosote was a poor growth substrate when provided as sole carbon source in a basal salts solution (BSM). Alternatively, peptone, yeas t extract or glucose in BSM supported high growth rates, but community five could not subsequently degrade pyrene. A combination of creosote and yeast extract in BSM (CYEM) supported growth and maintained the pyrene-degrading capacity of community five. Optimum pyrene-degrading activity occurred whe n the inocula were grown in creosote and yeast extract concentrations of 2 ml L-1 and 1 g L-1 respectively: concentrations outside these values result ed in either low biomass yields or loss of PAM-degrading activity. CYEM-gro wn community five inocula degraded 250 mg L-1 of pyrene in BSM at a rate co mparable to cultures inoculated with community five grown in BSM-pyrene. Ho wever, the CYEM-grown community showed a 40% lower rate of PAH degradation in a synthetic PAH mixture compared with pyrene-grown cells and there was a n increase in the lag period before the onset of PAH degradation. This appe ars to reflect a weaker induction of PAH catabolism by CYEM compared to BSM -pyrene.