Isolation of an Acetic Acid Bacterium Acetobacter pasteurianus CK-1 and Its Fermentation Characteristics

To effectively isolate acetic acid bacteria for producing makgeolli vinegar, various products were researched, and Acetobacter pasteurianus CK-1, a strain that is excellent in acetic acid production, was finally isolated. The optimal growth temperature of the isolated strain was confirmed to be 30℃, and it grew well in the pH range of 5.5~6.5, with optimal growth at pH 6. A. pasteurianus CK-1 had the most active proliferation when the initial ethanol concentration in the medium was 4%, and growth was possible even at an ethanol concentration of 7%. When inoculating the isolated strain into makgeolli to induce acetic acid fermentation, the pH at the beginning of fermentation was 3.54, which was gradually lowered to 2.77 after 18 days of fermentation. The acidity was 0.75% at the beginning of fermentation and gradually started to increase from the 4th day of fermentation. The final acidity at the end of fermentation was 5.54%. In the vinegar fermented by inoculating A. pasteurianus CK-1, acetic acid content was detected to be as high as 3,575.7±48.6 mg%, and the malic acid and citric acid contents were 2,150.8±27.6 and 55.8±3.7 mg%, respectively. Further, it was confirmed that the content and ratio of the organic acids produced significantly differed depending on the type of inoculated bacterial strain. During acetic acid fermentation, the populations of yeast and A. pasteurianus CK-1 were inversely changed. In the initial stage of fermentation, yeast dominated, and after 10 days of fermentation, A. pasteurianus CK-1 slowly proliferated and reached stationary phase.

초산균 Acetobacter pasteurianus CK-1의 분리 및 발효 특성

막걸리 식초 생산에 효과적인 초산균을 분리하기 위해 다양한 시료에서 초산균을 검색하였고, 그 중 초산 생산이 우수한 균주인 Acetobacter pasteurianus CK-1을 최종 분리하였다. 분리균주의 최적 생육온도는 30.0℃로 확인되었고, pH 6.0에서 가장 왕성하게 생장하였으며, pH 5.5~6.5 범위에서 잘 생장하였다. A. pasteurianus CK-1은 배지의 초기 에탄올 농도가 4%일 때 가장 왕성하게 생장하였고, 7%의 에탄올 농도에서도 생장이 가능하였다. 분리균주를 막걸리에 접종하여 초산 발효를 유도하였을 때, 발효 초기 pH 3.54였던 것이 발효가 진행되면서 점차 낮아져서 발효 18일 후에는 pH 2.77이 되었다. 산도는 발효 초기에 0.75%였던 것이 발효 4일경부터 점차 증가하여 최종 산도는 5.54%로 증가하였다. A. pasteurianus CK-1 발효 식초에서는 acetic acid가 3,575.7±48.6 mg%로 높게 검출되었고, malic acid와 citric acid는 각각 2,150.8±27.6 mg%와 55.8±3.7 mg%로 검출되었다. 접종한 균주의 종류에 따라 생성되는 유기산의 함량과 비율이 유의하게 차이가 나는 것을 확인하였다. 초산 발효 동안 발효액 내의 효모와 A. pasteurianus CK-1의 개체군은 반비례적으로 변화하였다. 발효 초기에는 효모가 우점하였으나, 발효가 진행됨에 따라 A. pasteurianus CK-1이 서서히 증식하여 10일 후에는 정체기에 이르렀다.