Emerging Contaminants Summit

Spring 2020

StudentCompetitionshiYing Shi
Texas A&M University 

Ying Shi is pursuing a Master of Science in Civil Engineering from Texas A&M University with a specialization in Environmental Engineering. She has worked on a variety of projects such as biodegradation of halogenated organic compounds, perfluoroalkyl substance and polyfluroroalkyl substance photodegradation with ZnO, as well as activated sludge systems. These projects involved degradation efficiency tests, biotransformation pathway analysis, phage hunting, etc. Ying Shi has relevant proficiency in GC/MS, GC/FID, Ion probes, Ion Chromatography, PCR, Miniprep Kit, SDS-PAGE, ELISA, Serial Cloner, and ChemDraw. She collaborated with a Ph.D. student on a poster for the 2017 ACS conference. They effectively removed 95% antimicrobial agent Triclosan using ZnO under UV light.



Biodesulfonation of 6:2 fluorotelomer sulfonates (6:2 FtS) and perfluorobutanesulfonic acid (PFBS)

Per- and poly-fluoroalkyl substances (PFASs) are synthetic chemicals commonly used in manufacturing of fluoropolymers and fluorinated surfactants, which have a wide range of applications in surface protection products and aqueous film-forming foams (AFFFs). Many long-chain PFASs are known to cause liver toxicity, changes in hormone and cholesterol levels, and impaired growth and development in laboratory studies. Since the phase-out of long chain PFASs, shorter chain length perfluoroakly substance like perfluorobutane sulfonate (PFBS) and polyfluroroalky substance like 6:2 fluorotelomer alcohol (6:2 FTOH) have been used as alternative compounds. For example, PFBS is used as water and stain protective coatings for carpets, paper and textiles, including Scotchgard products. New AFFFs formula contains fluorotelomer-based surfactants manufactured from 6:2 FTOH or its derivative, 6:2 fluorotelomer sulfonate 6:2 FtS.  Due to the limited numbers of subjects analyzed and studied, the implications of PFBS for human health and the environment is still unclear. However, the U.S. EPA has published the screening value of 15 µg/L of PFBS in drinking water and 7 µg/L in groundwater.

No biotransformation of PFBS has been reported and no 6:2 FtS biotransformation was observed in anaerobic sediment over 100 days or in activated sludge over 90 days under anaerobic conditions. However, aerobic biodegradation of 6:2 FtS to 6:2 FTOH, which is more biodegradable, has been reported, suggesting that the enzymatic desulfonation step limited 6:2 FtS biotransformation in either aerobic or anaerobic condition. Based on 6:2 FtS molecular structure and previous literature regarding biotransformation of non-fluorinated straight-chain alkyl sulfonates, 6:2 FtS must be desulfonated first for further biotransformation to occur. Many soil bacteria are capable of deriving their sulfur (S) source via desulfonation of aromatic and/or aliphatic sulfonates under S-limited conditions. Accordingly, we hypothesize that bacteria capable of desulfonating aliphatic sulfonates can also desulfonate 6:2 FtS and PFBS.   

In this study, we have successfully isolated a number of desulfonating bacteria from soils collected near rhizosphere as well as from runoff and soils contaminated with detergent at car wash facilities. The isolates are capable of using ethanesulfonic acid salt as S source. Several of our isolates have shown growth active growth on sulfur-free basal media agar plate containing glucose and 6:2 FtS, suggesting these isolates 


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