Remediation Technologies - Environmental Investigation and Remediation - page 340

Strain ENV478 degradation rates for bacteria grown on THF were as follows (TSS is a sur-
rogate for biomass):

Organic Contaminant Rate per Gram of TSS (mg/h)

1,4-Dioxane 21

1,3-Dioxolane 19

THF 63

BCEE 12

MTBE 9.1

The BCEE degradation rates were about threefold higher after ENV478 growth on propane
(32 mg/h/g of TSS) than after ENV478 growth on THF, and MTBE degradation resulted in
the accumulation of tert -butyl alcohol.

occur in the lactone form. The lactonization of 2HEAA produces PDX, as identii ed in the study of
Woo et al. (1977). The initial monooxidation of 1,4-dioxane likely results in the production of 1,4-
dioxane-2-ol, the hemiacetal of 2-hydroxyethoxy-2-acetaldehyde. A proposed degradation pathway
for the biodegradation of 1,4-dioxane by Strain ENV478 is shown in Figure 7.5.
Strain ENV478, when i rst grown on THF, degraded 1,4-dioxane at an initial rate of ~21 mg/h/g
of TSS, which was approximately one-third the rate at which ENV478 degraded THF. When the
THF and 1,4-dioxane were added together in equal amounts, 1,4-dioxane degradation did not occur
until all the THF in the medium had been degraded ( Figure 7.6 ). When Strain ENV478 cells grown
on THF were incubated with both 1,4-dioxane and 1,3-dioxolane, they degraded both compounds
simultaneously at approximately the same rate (Vainberg et al., 2006).
Much slower cell growth and lower 1,4-dioxane degradation rates (per gram of TSS) were
observed when Strain ENV478 was grown on sucrose (0.71 mg/h), yeast extract (1.1 mg/h), sodium
lactate (0.6 mg/h), 2-propanol (1.5 mg/h), and propane (3.2 mg/h). After growing on lactate, the
strain also degraded 1,3-dioxolane (1.0 mg/h). The team concluded that Strain ENV478 has a low
level of constitutive activity with these ethers. The team also found that Strain ENV478 does not

OH

H

O O OH

C

O

O

O O

1,4-dioxane 1,4-dioxane-2-ol

2-hydroxyethoxy-
2-acetaldehyde

O +H 2 O

O

HOH 2 C COOH

-H 2 O

O

O

1,4-dioxane-2-one
(PDX)

2-hydroxyethoxyacetic
acid

FIGURE 7.5 Proposed partial pathway for biodegradation of 1,4-dioxane by strain ENV478. (From Vainberg,
S., McClay, K., Masuda, H., et al., 2006, Applied and Environmental Microbiology 72(8): 5218-5224. With
permission.)