Luo, S.G., S.C. Chen, W.Z. Cao, W.H. Lin, Y.T. Sheu, and C.M. Kao.
Chemosphere 237:124449(2019)

Gamma poly-glutamic acid (γ-PGA) was used as the primary carbon and nitrogen source to bioremediate TCE-contaminated groundwater in a pilot-scale study. A 40L γ-PGA solution was injected into the aquifer via an injection well (IW) for substrate supplement. Groundwater samples were collected from monitor wells and the IW periodically and analyzed for TCE and its byproducts, geochemical indicators, dechlorinating bacteria, and microbial diversity. Injecting γ-PGA resulted in increased total organic carbon (up to 9820 mg/L in the IW), which biodegraded, causing anaerobic conditions to form. Increased ammonia concentration caused neutral groundwater conditions, benefitting the growth of Dehalococcoides. The negative zeta potential and micro-scale diameter of γ-PGA allowed its globule to distribute evenly within soil pores. After 59 days, up to 93% of TCE removal was observed, from 0.14 to 0.01 mg/L, and TCE dechlorination byproducts were also biodegraded. Next-generation sequence analyses revealed that reductive dechlorinating conditions caused variations in microbial diversity and dominant bacterial species. The dominant four groups of bacterial communities including dechlorinating bacteria, vinyl chloride degrading bacteria, hydrogen-producing bacteria, and carbon biodegrading bacteria.