Synthetic macrocyclic musk ethylene brassylate (EB)-degrading bacteria were isolated from the soil around Mount Takao, Tokyo, Japan. The bacteria grew well in cultures with EB as the only carbon source and were identified as belonging to the Betaproteobacteria and Firmicutes based on 16S rRNA sequence analysis. Analysis of the culture broth using EB as the only carbon source revealed that ethylene glycol and brassylic acid were produced as metabolic intermediates. An EB degradation pathway was proposed along with the assimilation data. Degradation tests using macrocyclic musks revealed that strain 3d preferentially degraded EB, whereas strain 11L degraded various macrocyclic musks with ester bonds. This difference in degradative specificity was reflected in the resting-cell reaction, suggesting that the first step, ester hydrolysis, was the limiting step for degradation. These findings demonstrate EB degradation using a single isolate. The EB degrading strains 3d and 11L, belonging to Xenophilus sp. and Bacillus sp., respectively, were selected for their degradative substrate specificity. Neither strain degraded cyclopentadecanone, suggesting that these strains initially degraded the tested compounds via ester hydrolysis. Strain 11L degraded all macrocyclic ester musks, including EB, pentadecanolide, hexadecanolide, and ω-6-hexadecenlactone, whereas strain 3d degraded only EB, suggesting that the biodegradability of macrocyclic ester musks depends on their structure.
Matsui et al. (Sat,) studied this question.