The dechlorination of TCE by a perchlorate reducing consortium

We enriched a trichloroethene (TCE)-dechlorinating consortium from a perchlorate-reducing bacterial culture (PRB) with a very low initial abundance of Dehalococcoides by feeding the culture lactate and TCE; named the novel culture perchlorate-reducing dechlorinating bacteria (PRTB). Short batch tests showed that the PRTB consortium reduced up to 0.45 mmol/L of TCE to non-toxic ethene in eight days after two additions of TCE and simultaneously reduced up to 0.15 mmol/L of ClO₄ ⁻to Cl⁻. TCE reduction by PRTB was sensitive to oxygen: 0.2 mg/L of oxygen delayed reduction of TCE to ethene from 5 to 15 days, while ⩾0.5 mg/L of oxygen significantly inhibited TCE reduction, causing vinyl chloride accumulation. After the consortium was enriched twice with TCE, the Dhc gene (reflecting the abundance of Dehalococcoides) increased from 1.14 × 10⁴to 3.25 × 10⁸copies/mL. The original PRB culture was dominated by Proteobacteria (78.4%), but the enriched PRTB culture was dominated by Chloroflexi (57.7%). The relative abundance of Dehalococcoides increased from 0.02% to 57.4%. Other presumptive dechlorinators Desulfuromonas and Geobacter were enriched as well. Possible acetogens (Spirochaetes) and putative fermenters (Bacteroidetes and Desulfovibrio) were also present in the culture, providing Dehalococcoides with acetate as the carbon source, hydrogen gas as the electron donor, and Vitamin B₁₂as a growth factor.