BIODEGRADATION OF PHENOLIC-COMPOUNDS BY SULFATE-REDUCING BACTERIA FROM CONTAMINATED SEDIMENTS

The biodegradation of phenolic compounds under sulfate-reducing condit ions was studied in sediments from northern Indiana. Phenol, p-cresol and 4-chlorophenol were selected as test substrates and added to sedim ent suspensions from four sites at an initial concentration of 10 mg/l iter. Degradative abilities of the sediment microorganisms from the fo ur sites could be related to previous exposure to phenolic pollution. Time to onset of biodegradation of p-cresol and phenol in sediment sus pensions from a nonindustrialized site was approximately 70 and 100 da ys, respectively, in unacclimated cultures. In sediment slurries from three sites with a history of wastewater discharges containing phenoli cs, time to onset of biodegradation was 50-70 days for p-cresol and 50 -70 days for phenol in unacclimated cultures. In acclimated cultures f rom all four sites, the length of the lag phase was reduced to 14-35 d ays for p-cresol and 25-60 days for phenol. Length of the biodegradati ve phase varied from 25 to 40 days for phenol and 10 to 50 days for p- cresol and was not markedly affected by acclimation. Substrate mineral ization by sulfate-reducing bacteria was confirmed with radiotracer te chniques using an acclimated sediment culture from one site. Addition of molybdate, a specific; inhibitor of sulfate reduction, and bacteria l cell inactivation inhibited sulfate reduction and substrate utilizat ion. None of the sites exhibited the ability to degrade 4-chlorophenol , nor were acclimated phenol and p-cresol degrading cultures from a pa rticular site able to cometabolize 4-chlorophenol.