Preparation and Preservation of Freeze-dried Cells of Acetic Acid Bacteria with Aldehyde Oxidase Activity

Freeze-dried cells of acetic acid bacteria were prepared to use as an additive for manufacturing and processing foods. When the freeze-dried cells were stored for 1 week at 5 degrees C, however, more than 50% of the original activity of aldehyde oxidase (AOX) was lost. It was found that this decrease in AOX was caused by damage to both the membrane-bound aldehyde dehydrogenase and terminal oxidase activities involved in the aldehyde oxidase electron transport system of acetic acid bacteria. The addition of 30% sucrose to the cell suspension prepared in a McIlvaine buffer (pH 6) before lyophilization was found to be effective for preventing the decrease of AOX activity. Cells freeze-dried in this way lost no AOX activity at all during first 3 weeks of storage at 5 degrees C and, even after 9 weeks, 80% of the original activity remained.