Regiospecific internal desaturation of aliphatic compounds by a mutant Rhodococcus strain

Abstract

A mutant Rhodococcus strain lacking the ability to utilize 1-chlorohexadecane was found to cis-desaturate aliphatic compounds, such as 1-chlorohexadecane, n-hexadecane, and heptadecanonitrile, yielding corresponding products with a double bond mainly at the ninth carbon from the terminal methyl groups. A new oxidative pathway involving the cis-desaturation step was suggested for alkane utilization by Rhodococcus spp.

FIG. 1

Gas chromatogram of an unidentified product generated from 1-chlorohexadecane by resting cells of Rhodococcus sp. strain KSM-B-3M. Resting cells (1 g [wet weight]) were added to the reaction medium containing 20 ml of 0.25 M phosphate buffer (pH 7.0) and 1 ml of 1-chlorohexadecane, and the cell suspension was placed in a 500-ml flask. The flask was incubated, with shaking, at 30°C for 3 days on a rotary shaker. Residual substrate (S) and an unidentified product (P) were extracted with n-hexane and detected by analysis with a GC with n-heptadecane (I) as an internal standard.

FIG. 2

Mass spectrum of the alkylthiolated product generated from 1-chlorohexadecane by resting cells of Rhodococcus sp. strain KSM-B-3M. The product extracted with n-hexane was evaporated. Approximately 0.2 mg of product was treated with 2.0 ml of dimethyl disulfide containing 6 mg of I₂ for 30 min at room temperature under argon gas atmosphere. The alkylthiolated product was then analyzed by GC-MS.