Utilization of Trimethylamine by a Penicillium Strain Isolated from Salted Fish

It has been generally believed that trimethyl amine (TMA) produced by bacteria through the reduction of trimethylamine N-oxide (TMO) during spoilage of fish is not further utilized by microorganisms, although a few papers1-4) have been published on the presence of TMA utilizing bacteria in soil, water etc. We found during a work on the preservation of salted fish muscle at a low temperature that the amount of TMA did not increase when molds grew abundantly on the sur face of the fish muscle homogenates, and that a strain of the molds isolated from the homogenates utilized TMA rapidly. In the present paper the ability of this mold to utilize TMA was studied, in comparison with that of several authentic cul tures of molds. The mold (strain F2) isolated from the fish muscle homogenates was tentatively classified, on the basis of morphological characteristics, to genus Penicillium (probably to the P. nigricans series). This organism grew well in Czapeck's medium5) which was prepared to contain 5mg-N % TMA as the sole source of nitrogen in place of NaNO3. As shown in Fig. 1, in the presence of nitrate TMA in the culture was utilized after nitrate had disappeared from the medium. This mold also grew in the media which contained dimethyla mine, methylamine, ammonia, choline, betaine, dimethylglycine, sarcosine or glycine as the sole soure of nitrogen. However, the utilization by this organisms of TMO was not detected during the first 10 days' incubation. The activity of TMA decomposition in this mold was not found in its intact cell suspension or its cell homogenate. The starved cell suspension of this mold, however, showed the high activity of TMA decomposition. In the course of decomposi tion of TMA in a reaction system containing the starved cell suspension TMO was not produced. In order to obtain further information about the distribution of the ability to utilize TMA in the molds, 23 authentic strains of molds which be long to genera Penicillium, Aspergillus, Rhizopus, Mucor, Citromyces and Alternaria were examined in respect to this ability. The results indicated that 8 of the 11 strains of Penicillium, 1 of the 8 strains of Aspergillus, and none of the Rhizopus, Mucor, Citromyces and Alternaria strains utilized TMA. The strains which were found to have the ability to utilize TMA were P. glaucum, P. notatum, P. caseicolum, P. camemberti, P. citrinum, P. spinulosum, P. expansum, P. puberulum and A. tamarii. These molds may be utilizable in the food industry in case that the removal of TMA from food materials is desired. Further taxonomical characteristics of the mold and detailed mechanisms involved in the decompo sition of TMA by the mold will be published elsewhere. Tateo FUJII, Yuzaburo ISHIDA and Hajime KADOTA Laboratory of Microbiology, Department of Fisheries, Faculty of Agriculture, Kyoto University, Kyoto