Stable isotope fractionation of tetrachloroethene during reductive dechlorination by Sulfurospirillum multivorans and Desulfitobacterium sp strain PCE-S and abiotic reactions with cyanocobalamin

Carbon stable isotope fractionation of tetrachloroethene (PCE) during reductive dechlorination by whole cells and crude extracts of Sulfurospirillum multivorans and Desulfitobacterium sp. strain PCE-S and the abiotic reaction with cyanocobalamin (vitamin B-12) was studied. Fractionation was largest during the reaction with cyanocobalamin with alpha C = 1.0132. Stable isotope fractionation was lower but still in a similar order of magnitude for Desulfitobacterium sp. PCE-S (alpha C = 1.0052 to 1.0098). The isotope fractionation of PCE during dehalogenation by S. multivorans was lower by 1 order of magnitude (alpha C = 1.00042 to 1.0017). Additionally, an increase in isotope fractionation was observed with a decrease in cell integrity for both strains. For Desulfitobacterium sp. strain PCE-S, the carbon stable isotope fractionation factors were 1.0052 and 1.0089 for growing cells and crude extracts, respectively. For S. multivorans, alpha C values were 1.00042, 1.00097, and 1.0017 for growing cells, crude extracts, and the purified PCE reductive dehalogenase, respectively. For the field application of stable isotope fractionation, care is needed as fractionation may vary by more than an order of magnitude depending on the bacteria present, responsible for degradation.