Isolation of dimethyl sulfone-degrading microorganisms and application to odorless degradation of dimethyl sulfoxide.

With the objective of developing an odorless biodegradation process for dimethyl sulfoxide (DMSO), Hyphomicrobium sp. WU-OM3 was isolated. During the cultivation of strain WU-OM3 cells with 20 mM dimethyl sulfone (DMSO2) as the sole carbon source, DMSO2 was completely consumed within 48 h and sulfate ion accumulated in the culture broth. Methanesulfonate was also detected as an intermediate of DMSO2 degradation. By combining the DMSO-oxidizing microorganism and strain WU-OM3 cells, 0.64 mM (50 mg/l) DMSO was degraded to sulfate ion with 80% molar conversion ratio.

Oxidative degradation of dimethyl sulfoxide by Cryptococcus humicolus WU-2, a newly isolated yeast.

A dimethyl sulfoxide (DMSO)-degrading yeast strain Cryptococcus humicolus WU-2 was isolated and characterized. When 0.64 mM (50 mg/l) DMSO was added as the sole source of sulfur, DMSO was completely consumed by WU-2 in 48 h and oxidized to dimethyl sulfone with a molar conversion ratio of 83%. WU-2 also oxidized alkyl sulfides such as dimethyl sulfide, ethyl methyl sulfide and diethyl sulfide into the corresponding sulfones, which are odorless compounds.

Continuous degradation of dimethyl sulfoxide to sulfate ion by Hyphomicrobium denitrificans WU-K217.

With the objective of removing dimethyl sulfoxide (DMSO) contained in wastewater from semiconductor or liquid crystal display factories, biodegradation of DMSO, particularly at a low concentration, was examined. Through the screening of DMSO-degrading microorganisms, Hyphomicrobium denitrificans WU-K217 utilizing DMSO as the sole source of carbon was isolated from soil. DMSO at less than 20 mM was degraded to sulfate ion by WU-K217 with 100% molar conversion ratio based on DMSO added during 60-h cultivation at 30 degrees C under aerobic conditions. Even in the presence of 116 mM or 225 mM DMSO, WU-K217 showed growth although the amount of DMSO degraded was only 33 mM or 10 mM, respectively. Similar to the growing cells, the resting cells of WU-K217 degraded DMSO at over a wide range of temperature, 20-40 degrees C. The highest DMSO-degradation activity was obtained at 30 degrees C, and 0.64 mM (50 mg/l) DMSO was completely degraded to sulfate ion with 100% molar conversion ratio within only 15 min. Furthermore, to examine whether WU-K217 would be useful for the removal of DMSO contained in wastewater exhausted in large amounts, continuous degradation of DMSO was examined. When 0.64 mM DMSO was added to the resting cells periodically at 15-min intervals, DMSO was completely degraded to sulfate ion without any decrease of the degradation activity at least during the twelve times of DMSO addition.