subtaxa of A. oryzae, which let to great progress in producing shōchū in Japan. Since then, aspergillus developed by Kawachi has also been used for soju and makgeolli in Korea. Yellow kōji (A. oryzae etc.) is used to produce sake, and at one time all honkaku shōchū. However, yellow kōji is extremely sensitive to temperature; its moromi can easily sour during fermentation. This makes it difficult to use in warmer regions such as Kyūshū, and gradually black and white kōji became more common in production of shōchū. Its strength is that it gives rise to a rich, fruity, refreshing taste, so despite the difficulties and great skill required, it is still used by some manufacturers. It is popular amongst young people who previously had no interest in typically strong potato shōchū, playing a role in its recent revival. Thus, white and black kōji are mainly used in the production of shōchū, but only yellow kōji (A. oryzae) is usually used in the production of sake. White kōji (A. kawachii etc.) was discovered as a mutation from black kōji by Genichirō Kawachi in 1923. This effect was researched and white kōji was successfully grown independently. White kōji is easy to cultivate and its enzymes promote rapid saccharization; as a result, it is used to produce most shōchū today. It gives rise to a drink with a refreshing, mild, sweet taste. Black kōji (A. awamori also known as A. luchuensis etc.) is mainly used to produce shōchū and awamori. In 1901, Tamaki Inui, lecturer at University of Tokyo succeeded in the first isolating and culturing. In 1910, Genichirō Kawachi succeeded for the first time in culturing var. kawachi, a variety of subtaxa of A. awamori. This improved the efficiency of shōchū production. It produces plenty of citric acid which helps to prevent the souring of the moromi. Of all three kōji, it most effectively extracts the taste and character of the base ingredients, giving its shōchū a rich aroma with a slightly sweet, mellow taste. Its spores disperse easily, covering production facilities and workers' clothes in a layer of black. Such issues led to it falling out of favour, but due to the development of new kuro-kōji (NK-kōji) in the mid-1980s, interest in black kōji resurged amongst honkaku shōchū makers because of the depth and quality of the taste it produced. Several popular brands now explicitly state they use black kōji on