Isolation and characterization of bacterial strains that have high ability to degrade 1,4-dioxane as a sole carbon and energy source.

Four novel metabolic 1,4-dioxane degrading bacteria possessing high ability to degrade 1,4-dioxane (designated strains D1, D6, D11 and D17) were isolated from soil in the drainage area of a chemical factory. Strains D6, D11 and D17 were allocated to Gram-positive actinomycetes, similar to previously reported metabolic 1,4-dioxane degrading bacteria, whereas strain D1 was allocated to Gram-negative Afipia sp. The isolated strains could utilize a variety of carbon sources, including cyclic ethers, especially those with carbons at position 2 that were modified with methyl- or carbonyl-groups. The cell yields on 1,4-dioxane were relatively low (0.179-0.223 mg-protein (mg-1,4-dioxane)(-1)), which was likely due to requiring energy for C-O bond fission. The isolated strains showed 2.6-13 times higher specific 1,4-dioxane degradation rates (0.052-0.263 mg-1,4-dioxane (mg-protein)(-1) h(-1)) and 2.3-7.8 fold lower half saturation constants (20.6-69.8 mg L(-1)) than the most effective 1,4-dioxane degrading bacterium reported to date, Pseudonocardia dioxanivorans CB1190, suggesting high activity and affinity toward 1,4-dioxane degradation. Strains D1 and D6 possessed inducible 1,4-dioxane degrading enzymes, whereas strains D11 and D17 possessed constitutive ones. 1,4-Dioxane degradation (100 mg L(-1)) by Afipia sp. D1 was not affected by the co-existence of up to 3,000 mg L(-1) of ethylene glycol. The effects of initial pH, incubation temperature and NaCl concentration on 1,4-dioxane degradation by the four strains revealed that they could degrade 1,4-dioxane under a relatively wide range of conditions, suggesting that they have a certain adaptability and applicability for industrial wastewater treatment.

Evaluation of the biodegradation potential of 1,4-dioxane in river, soil and activated sludge samples.

To evaluate the biodegradation potential of 1,4-dioxane in natural environments, a total of 20 environmental samples including river water, activated sludge, soil from the drainage area of a chemical factory and garden soil were subjected to a 1,4-dioxane degradation test. The five soil samples from the drainage area of the chemical factory were capable of reducing 100 mg l(-1) of 1,4-dioxane to below the detection limit (0.8 mg l(-1)) within 33 days. In one activated sludge sample, 100 mg l(-1) of 1,4-dioxane decreased by 69% within 14 days via cometabolic degradation in the presence of 100 mg l(-1) of tetrahydrofuran (THF). The ability of all samples to degrade 1,4-dioxane degradation with or without THF increased after repeated enrichment, except for one soil sample from the drainage area of the chemical factory that was no longer able to degrade 1,4-dioxane after the third cycle of enrichment. However, most of the samples (14/20) were not able to degrade 1,4-dioxane degradation. Thus, it can be concluded that the potential for 1,4-dioxane degradation is not ubiquitously distributed in natural environment.

Estimation of vitamin B1 excretion in 24-hr urine by assay of first-morning urine.

Urinary B1 (vitamin B1) excretion is commonly determined in 24-hr urine specimens to obtain an estimate of nutritional status. The aim of our study was to investigate whether B1 in random urine specimens, corrected for the urine creatinine (Cr), can be substituted for B1 in 24-hr urines. Collection of such hour urines is often fraught with errors; an alternative method is described here. All urine specimens voided over 24 hr were collected from 32 healthy adults as were the first-morning urines from 30 healthy Japanese women. The B1 excretion was expressed as the ratio of B1 to Cr. Although the B1 excretion was expressed as the B1/Cr ratio, the B1 excretion varied with the urine volume and the time of urine collection. The B1/Cr ratio in random urine specimens not collected at a fixed time may mislead the evaluation of the nutritional status. We found that the B1/Cr ratio in the first-morning urine correlated significantly with the ratio in 24-hr urines (r=0.970, P<0.001) and also with the concentration of total B1 (B1 plus its phosphate esters) in whole blood (r=0.733, P<0.001). We conclude that the B1/Cr ratio in 24-hr urines could be estimated by measuring the ratio in the first-morning urine.