In general, it is best to keep sake refrigerated in a cool or dark room, as prolonged exposure to heat or direct light will lead to spoilage. Sake stored at relatively high temperature can lead to formation of dicetopiperazine, a cyclo (Pro-Leu) that makes it bitter as it ages Sake has high microbiological stability due to its high content of ethanol, but incidences of spoilage have occurred. One of the microorganisms implicated in this spoilage is lactic acid bacteria (LAB) that has grown tolerant to ethanol and is referred to as hiochi-bacteria. Sake stored at room temperature is best consumed within a few months after purchase.