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Kinetic evidence for pentachlorophenol‐dependent growth of a dehalogenating population in a pentachlorophenol‐ and acetate‐fed methanogenic culture
Author(s) -
Stuart Sheryl L.,
Woods Sandra L.
Publication year - 1998
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19980220)57:4<420::aid-bit5>3.0.co;2-o
Subject(s) - pentachlorophenol , chemistry , population , bioreactor , reaction rate constant , chlorophenol , chromatography , kinetics , nuclear chemistry , environmental chemistry , organic chemistry , phenol , physics , demography , quantum mechanics , sociology
A method was developed to evaluate growth of a reductively dechlorinating bacterial population within a pentachlorophenol (PCP)‐ and acetate‐fed, mixed, methanogenic culture. In 6‐ to 12‐day experiments, a computer‐monitored/feedback‐controlled bioreactor was used to maintain constant pH, temperature, and acetate concentration, while transformation of multiple PCP additions was monitored. The potential at a platinum electrode, E Pt , was not controlled externally, but was maintained constant at −0.25 ± 0.002 V (vs. SHE) by iron sulfides in the medium and the activity of the culture. PCP was reductively dechlorinated at the ortho position, yielding 3,4,5‐trichlorophenol (3,4,5‐TCP) via 2,3,4,5‐tetrachlorophenol (2,3,4,5‐TeCP). Below an initial PCP concentration of 0.5 μ M, PCP was transformed to 3,4,5‐TCP within 3 to 6 h. Biomass concentration changes were small during this period, and PCP and 2,3,4,5‐TeCP transformations were modeled as pseudo‐first‐order reactions. Increases in pseudo‐first‐order rate constants for PCP and 2,3,4,5‐TeCP were directly related to the amount of PCP transformed to 3,4,5‐TCP, suggesting enrichment of a PCP‐catabolizing population. Moreover, rate constant increases were independent of the amount of acetate consumed, changes in the overall volatile suspended solids (VSS) concentration, and the experimental duration. When PCP was added to the reactor at increasingly shorter time intervals in an exponential pattern, pseudo‐first‐order rate constants increased exponentially. An average rate constant doubling time of 1.7 days (1.4 to 2.3 d) was estimated. While the VSS concentration of the culture increased 60% in an 8‐day period, pseudo‐first‐order rate constants increased by a factor of approximately 6. This large increase in transformation rate constants suggests growth of a bacterial population capable of using PCP and 2,3,4,5‐TeCP as terminal electron acceptors. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 420‐429, 1998.