Biodegradation kinetics of chlorinated ethylenes by Methylosinus trichosporium (OB3b)

Author

William Eng

Date of Award

12-1990

Degree Type

Thesis

Degree Name

Master of Science

Major

Microbiology

Major Professor

G. W. Strandberg

Committee Members

G. S. Sayler, D. C. White, A. V. Palumbo

Abstract

The focus of this work is on biodegradation of chlorinated ethylenes (CEs) by Methylosinus trichosporium strain OB3b. The compound trans-1,2-dichloroethylene was degraded at higher concentrations (6.52 mM) and faster rates than the other dichloroethylenes (DCEs). The degradation of cis-1,2-dichloroethylene and 1,1-DCE occurred only at concentrations under 309 and 206 μM, respectively. Using the Michaelis-Menten model, the maximum velocities (V_max) for 1,1-DCE, cis-1,2-DCE, trans-1,2- DCE, and TCE degradation were estimated to be 16, 28, 21,250 and 14 nmol/hr/mg protein, respectively. The respective Michaelis constants (K_m) were 83, 97.2, 973, and 105.7 μM. In a mixture of TCE and DCE, the extent of TCE degradation depended on the DCE isomer present and its concentration. Below 309 μM, trans-1,2-DCE did not inhibit TCE degradation. At 309 μM DCE, TCE degradation was completely inhibited with 1,1-DCE but to a lesser extent with cis-1,2-DCE. At 206 μM DCE, only 1,1-DCE inhibited TCE degradation. The addition of 6 μM of 1,1-DCE or tetrachloroethylene (PCE) resulted in a decrease of the V_max for trans-1,2-DCE degradation to 2.13, and 7.03 μmol/hr/mg protein, respectively. However, the V_max was unaffected when 6.3 μM TCE was present. The introduction of 1,1-DCE decreased the K_m for trans-1,2-DCE to 214 μM while PCE decreased it to 732 μM. In contrast, the K_m for trans-1,2-DCR was increased to 1399 μM by the addition of TCE. The inhibition of trans-1,2-DCE degradation by other CEs may be a combination of competitive and mixed noncompetitive interactions. Competitive inhibition was evident in the interaction between trans-1,2-DCE and TCE where The V_max for trans-1,2-DCE degradation was unchanged by the presence of TCE but the K_m was increased. Mixed-noncompetitive inhibition was evident in the inhibition of trans-1,2-DCE by PCE and 1,1-DCE, where the V_max and K_m were decreased.

Recommended Citation

Eng, William, "Biodegradation kinetics of chlorinated ethylenes by Methylosinus trichosporium (OB3b). " Master's Thesis, University of Tennessee, 1990.
https://trace.tennessee.edu/utk_gradthes/12637