2012 年 61 巻 3 号 p. 239-245
Lactose intolerant people in Asia are about 80% population. People with lactose intolerant do not produce enough of the lactase enzyme to break down lactose contained in milk and milk products. One method for prevention, reduction or improvement is lactase supplementation, and fungal lactase (β-galactosidase) is used generally. Characteristics of fungal lactase is stability at acidic pH. Acidic stability of three lactases produced by Aspergillus oryzae, Penicillium multicolor and Aspergillus niger are different. Lactase from A. niger is most stable among them, but low-reactivity at neutral pH. Amino acid sequence homology among three fungal lactases is more than 70%, but relation between lactase character and structure is unknown. In Japan, lactase for lactose intolerance is regulated as drug and it is hard to purchase generally. A. oryzae is known as ‘Koji’ used for japanese traditional fermented foods such as miso, syoyu and sake. For this reason, lactase produced by A. oryzae is thought to be safe. If lactase can be obtained like U.S. dietary supplement, it is expected that lactase supplementation will be known widely.