Screening for pentachlorophenol-degrading bacterial candidates for bioaugmentation in anaerobic bioprocesses and development of pentachlorophenol-induced toxicity bioassay.

Abstract

Refractory organic compounds, e.g. pentachlorophenol (PCP), have been reported to inhibit

bioprocesses during anaerobic wastewater treatment. PCP-induced toxicity compromises

treatment performance in these anaerobic biosystem possibly by affecting the stability of

indigenous microbial communities. In this study, anaerobic PCP-degrading bacterial

candidates were screened from environmental isolates for use in bioaugmentation in such

wastewater treatment. The strains were selected on the basis of their tolerance to PCP on agar

and their cell viability in liquid culture containing PCP. The isolates were also screened for

Desulfitobacterium spp., a genus established for its effectiveness in PCP biodegradation, by

colony polymerase chain reaction. The potential PCP-degrading candidates identified through

these screens would then need to be assessed for their capacity to degrade PCP. To this end, a

bioassay to measure PCP-induced toxicity was developed. Suitable bioindicators were first

selected – E. faecalis and L. acidophilus – and then model strains of PCP degrader

(Pseudomonas aeruginosa) and non-degrader (Escherichia coli) were tested to pilot the

bioassay. Residual PCP toxicity could be quantified by the growth of the bioindicators in the

supernatants collected from PCP-supplemented model strain cultures. Results obtained could

be used to assess PCP degradative capacity of a test strain or a consortium.