Production of Methanethiol from Methionine by Brevibacterium linens CNRZ 918

Abstract

The conditions under which B. linens CNRZ 918, a strain isolated from the surface smear flora of Gruyere de Comte'' cheese, produced methanethiol from methionine were studied. Demethiolation was estimated from the methanethiol production capacity of resting cells. Methionine was demethiolated mainly during the exponential growth phase of the organism during which time the cells were rod-shaped and had a generation time of 5 h, and the medium became alkaline. At the end of growth (pH 9) the cells were coccoid, and produced only very little methanethiol. The production of methanethiol required the presence of methionine in the culture medium, this reflecting the probable induction of the enzyme systems involved. Glucose favored growth and inhibited production of methanethiol. Lactate favored both growth and methanethiol production. Resting rod cells also produced methanethiol from structural analogs of methionine and from methionine-containing peptides. The apparent kinetic constants of the production of methanethiol for rod and coccoid cells were respectively Km = 14 mM and 46 mM, Vmax = 208 nanokatal (nkat)/g and 25 nkat/g. The optimum temperature and pH for production were 30.degree. C and pH 8. Azide or malonate favored the production of methanethiol by resting cells, whereas chloramphenicol had no effect.