Reductive dechlorination of 2,3-dichloroaniline by Dehalobacter in an anaerobic enrichment culture

Abstract

12,3-dichloroaniline (2,3-DCA) has widespread use in chemical manufacturing and remains a persistent groundwater contaminant. To better understand the pathway and kinetics of its reductive dechlorination, we conducted a laboratory kinetic experiment using an anaerobic enrichment culture dominated by Dehalobacter. At an initial field-relevant concentration of 40 mg/L, complete and stoichiometric dechlorination of 2,3-DCA to aniline via 2-CA was achieved. The intermediates, 2-chloroaniline (2-CA) and 3-chloroaniline, were transiently formed in a ratio of 8:1. The growth yields of Dehalobacter on 2,3-DCA and 2-CA were 1.2 {+/-} 0.1 x 108 and 1.3 {+/-} 0.1 x 108 16S rRNA gene copies/mol chloride, respectively. The maximum specific growth rate for 2,3-DCA, max, was 0.18 {+/-} 0.03 day-{superscript 1} with a half-saturation constant, Ks, at 45 {+/-} 16 mg /L. The first-order decay constant for Dehalobacter when starved of chlorinated electron acceptors was estimated at 0.017 {+/-} 0.001 day-{superscript 1}. Lactate fermentation, acetogenesis from ethanol, syntrophic propionate oxidation, and hydrogenotrophic methanogenesis were observed during dechlorination. This work provides insights into the organohalide respiration of 2,3-DCA to aniline and advances the understanding of microbial interactions during anaerobic dechlorination. These results offer guidance for developing stable dechlorinating microbial ecosystems and key kinetic parameters for predictive modeling of groundwater 2,3-DCA fate and transport. 3 SynopsisThis study demonstrated stoichiometric dechlorination of 2,3-dichloroaniline to aniline, characterized syntrophic interactions in a mixed anaerobic dechlorinating culture, and determined growth yield, first-order decay and Monod constants for Dehalobacter. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/639126v3_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@5d59c4org.highwire.dtl.DTLVardef@b05a3aorg.highwire.dtl.DTLVardef@1f39f6borg.highwire.dtl.DTLVardef@1676753_HPS_FORMAT_FIGEXP M_FIG C_FIG Created in BioRender. Wang, S. (2025) https://BioRender.com/f47t993