3-methylbutanal is known to contribute to a nutty aroma in cheese. A paper on a Lactococcus cremoris strain producing 3-methylbutanal has recently been published. Previous studies have reported that 3-methylbutanal is produced most efficiently at temperatures of 37°C or higher. However, in this strain, the highest production level was observed at the relatively low temperature of 20°C. The content of this paper is primarily derived from the master’s thesis research conducted by Hayashizaki.