The biodegradation potential of [14C]dimethylsilanediol, the monomer unit of polydimethylsiloxane, in soils was investigated. Dimethylsilanediol was found to be biodegraded in all of the tested soils, as monitored by the production of 14CO2. When 2-propanol was added to the soil as a carbon source in addition to [14C]dimethylsilanediol, the production of 14CO2 increased. A method for the selection of primary substrates that support cometabolic degradation of a target compound was developed. By this method, the activity observed in the soils was successfully transferred to liquid culture. A fungus, Fusarium oxysporum Schlechtendahl, and a bacterium, an Arthrobacter species, were isolated from two different soils, and both microorganisms were able to cometabolize [14C]dimethylsilanediol to 14CO2 in liquid culture. In addition, the Arthrobacter sp. that was isolated grew on dimethylsulfone, and we believe that this is the first reported instance of a microorganism using dimethylsulfone as its primary carbon source. Previous evidence has shown that polydimethylsiloxane is hydrolyzed in soil to the monomer, dimethylsilanediol. Now, biodegradation of dimethylsilanediol in soil has been demonstrated.

Abstract-Previous studies have shown that polydimethylsiloxane is hydrolyzed

Previous studies have shown that polydimethylsiloxane is hydrolyzed in soil to dimethylsilanediol and that dimethylsilanediol is biodegraded in soil. Previously, two soil microorganisms capable of biodegrading dimethylsilanediol were isolated and identified. In this paper, the extent of [ 14 C]dimethylsilanediol biodegradation by these two soil microorganisms, Fusarium oxysporum Schlechtendahl and an Arthrobacter species, is investigated. The silicon-containing products of dimethylsilanediol biodegradation in liquid culture were identified by high-performance liquid chromatography coupled to argon plasma emission spectrometry (HPLC-ICP). The biodegradation of [ 14 C]methylsilanetriol was investigated in liquid cultures and in soil by monitoring the production of 14 CO 2 . The sorption coefficient of [ 14 C]methylsilanetriol was determined, and the sorption coefficient of [ 14 C]dimethylsilanediol was estimated, by measuring the amount of 14 C counts in the water phase of a water-soil mixture. Methylsilanetriol was found to be mineralized in liquid cultures of F. oxysporum Schlecht. and the Arthrobacter sp. that were supplied with a primary carbon source. However, the production of 14 CO 2 from [ 14 C]methylsilanetriol in soil experiments never exceeded the level of possible [ 14 C]-containing impurities in the methylsilanetriol. Methylsilanetriol was found to be more strongly sorbed to soil, which might have reduced its bioavailability. Previous evidence has shown that polydimethylsiloxane is hydrolyzed in soil to the monomer dimethylsilanediol, which is biodegraded in soil. Now mineralization of dimethylsilanediol to inorganic silicate has been demonstrated.