Effects of fermentation temperatures on amounts of intracellular sulfur compounds in yeast and the activity of methionineadenosyltransferase (MATFase) during fermentation in sake mash and in parallel fermentation media were studied using Kyokai No.7 yeast. Result showed there was no difference in the activity of MATFase in K-7 yeast cultured between 10°C and 15°C. It is clear that there were no relations between the accumulation of s-adenosylmethionine (SAM) and activity of MATFase intracellularly during mash fermentation at low temperature. We propose a parallel-fermentation for sake moromi mash, using a GYP-rich agar medium, component of glucose, yeast extract and polypepton with a liquid glucose medium in the flask. The phenomenon of an accumulation of SAM in intracellular yeast at low temperature, which occurred only with the moromi mash, could be confirmed with this medium. From the above, it seems important that amino acids be supplied little by little during fermentation. It is suggested that parallel-fermentation is concerned with the uptake of methionine of the yeast at low temperatures.