Bioremediation potential of immobilized aerobic consortia dechlorinating 1,2-DCA

1,2-dichloroethane (1,2-DCA) is a persistent and probably carcinogenic groundwater contaminant. Under suitable conditions, 1,2-DCA can be biodegraded by specialized microorganisms by anaerobic and aerobic pathways that can be exploited in bioremediation. Although anaerobic pathways are usually more studied, hydrolytic aerobic biodegradation seems a promising alternative. Currently, the only known hydrolytic pathway is mediated by the key enzyme haloalkane dehalogenase DhlA, encoded by the dhlA gene, carried by a few isolates within the Xanthobacteriaceae family. In this work, the dechlorinating potential of newly isolated aerobic 1,2 DCA degrading consortia was evaluated to be exploited in bioremediation strategies based on bioaugmentation with immobilized degrading bacteria. Six 1,2-DCA dechlorinating consortia were isolated from 1,2-DCA contaminated groundwater through enrichment cultures on mineral salt medium amended with 1,2-DCA as sole carbon source and subsequent transfer on solid medium. Chemical monitoring performed over time (on four of the six consortia) by Cl- release assay and Gas Chromatography-Mass Spectrometry (GC-MS) revealed stable 1,2-DCA removal capacity by all consortia. The Whole Genome Sequencing revealed the presence of genera including known aerobic 1,2-DCA degraders (Ancylobacter, Starkeya, Xanthobacter) and other genera whose role in the consortia is yet unclear. All consortia carried a dhlA gene fragment 100% identical to that of other known aerobic 1,2-DCA degraders, and other genes involved in the hydrolytic 1,2-DCA degradative pathway. The consortia were tested for the ability to form 1,2-DCA-degrading biofilms on biodegradable biopolymeric polylactic acid (PLA) scaffolds made by electrospinning. Scanning Electron Microscopy observations and GC-MS monitoring revealed the consortia can form a biodegrading biofilm on biopolymeric scaffolds that maintains its properties after being transferred to a new system. Successful immobilization on biopolymeric supports suggests the potential application of the dechlorinating consortia-scaffold system as a bioremediation device.