The fermentation process of sake is a multiple parallel fermentation, which is unique to sake. Multiple parallel fermentation is the conversion of starch into glucose followed by immediate conversion into alcohol. This process distinguishes sake from other liquors like beer because it occurs in a single vat, whereas with beer, for instance, starch to glucose conversion and glucose to alcohol conversion occur in separate vats. The breakdown of starch into glucose is caused by the kōji-kin fungus, while the conversion of glucose into alcohol is caused by yeast. Due to the yeast being available as soon as the glucose is produced, the conversion of glucose to alcohol is very efficient in sake brewing. This results in sake having a generally higher alcohol content than other types of liquor.