Isolation and characterization of bacteria that degrade poly (lactic acid-glycerol ester)-type time- release electron donors for accelerated biological reductive dechlorination

Hydrogen Release Compound (HRC ) is an important electron donor that has recently become available and is now becoming widely applied to the accelerated biological reductive dechlorination of chloroethenes such as tetrachloroethene (PCE) and trichloroethene (TCE). HRC is a benign poly(lactic acid-glycerol ester) specially formulated for the slow time-release of lactic acid. Lactic acid is then metabolized to hydrogen, which can be used in the reductive dechlorination of chloroethenes. To establish an advance diagnosis of the HRC addition effect for the bioremediation of polluted sites, 17 strains of HRC-degrading bacteria were isolated by liquid- and plate-culture methods. All these strains could grow on a basal medium containing purified HRC as the sole carbon source. The sequence analysis of the 16S rDNAs of 6 of the 17 strains shows that they all belong to the family β-Proteobacteria, which includes Burkholderia cepacia, Burkholderia vietnamiensis, Ralstonia sp., and Variovorax paradoxus. The time course of HRC degradaton by strains JM-11, JM-12 and JM-13 showed that the HRC degradation rates after 9 days of cultivation were 81.1%, 82.8% and 80.4%, respectively. Preliminary assay of the activities of the HRC-degrading enzyme indicated that HRC degradation may be specifically performed by specific lipases produced by HRC-degrading microorganisms.