Soil organic matter and nutrient availability affect the applicability of low-carbon energy source in Dehalococcoides-augmented soil.

Dehalococcoides is a functional microorganism that completely dechlorinates trichloroethene (TCE). Augmentation with pure Dehalococcoides is important for reducing environmental disturbances that accompany bioaugmentation. However, the applicability of Dehalococcoides -bioaugmentation to contaminated soils is unclear. In this study, seven low-carbon energy sources (methanol, formate, acetate, ethanol, lactate, citrate, and benzoate) were used as electron donors for Dehalococcides to evaluate its applicability in remediating TCE-contaminated soils. Soil microcosms supplemented with ethanol, formate, or lactate showed relatively high dechlorination activity within 111–180 days. The functional gene profiles predicted by PICRUSt2 from 16 S rRNA gene sequences were similar in the proportions of dehydrogenases, which initiate electron donor oxidation, in all soils and did not seem to reflect Dehalococcoides -bioaugmentation applicability. Soils with higher organic matter content (>3.2%; dry weight base) and protein concentration (>1.6 µg/mL) supported complete dechlorination. These results suggest that organic matter and nutrient availability mainly affect successful TCE dechlorination in Dehalococcoides -augmented soils. The study offers significant experimental support for comprehending the suitability of low-carbon energy sources in successful bioaugmentation, aiming to mitigate environmental disturbances associated with the process. [Display omitted] • Ethanol, formate, and lactate are low-carbon energy sources for effective dechlorination. • Formate supplementation achieved the fastest and most complete dechlorination within 111–180 days. • Soils with higher organic matter content and protein concentration supported complete dechlorination. [ABSTRACT FROM AUTHOR]