Abstract
The objective of this study was to control Kimchi fermentation using pH sensitive bacteriocin entrapping liposome(bacteriocin-liposome). The liposomes were prepared by the reverse-phase evaporation method from a mixture of DPPC(dipalmitoyl phosphatidylcholine, DPPE(dipalmitoyl phosphatidylethanolamine), DOPC(dioleoyl phosphatidylcholine) and cholesterol in a molar ration of 4:2:1:4. The bacteriocin-liposome was disruptured at pH 4 of buffer and was stable at alkaline pHs(6 and 7). Irrespective of the addition of the bacteriocin-liposomes, the pH of every Kimchi sample decreased to 5 during 5 days storage at 5$^{\circ}C$. Kimchi samples treated with bacteriocin-liposomes maintained pH 4 or higher, while Kimchi samples not treated with bacteriocin-liposomes exhibited pH 3.58 or lower. In general, the pH of Kimchi samples stored at 20$^{\circ}C$ decreased faster, compared to that of Kimchi samples stored at 5$^{\circ}C$. The pH of Kimchi samples treated with the bacteriocin-liposomes was 3.9 during 90 days storage, while that of the samples not treated with the bacteriocin-liposomes was 3.68 and 3.32 during 30 days and 90 days storages, respectively. Lactic acid bacteria in Kimchi treated with the bacteriocin-liposome grew relatively slow at 5$^{\circ}C$. The viable cell number of lactic acid bacteria increased up to 4${\times}$10$\^$7/ cells/ml and then decreased to 8${\times}$10$\^$6/ cells/ml during 90 days storage at 5$^{\circ}C$.
발효식품의 후산발효를 조절하기 위하여 pH sensitive liposome의 이용 가능을 검토하였다. Lactococcm sp. CU216이 생산하는 박테리오신은 L.. acidophilus를 제외하고는 대부분의 유산균주들에 생육억제 효과가 있는 것으로 확인되었으며, 이를 Octyl-Sepharose column으로 분획하여 정제하였다. 정제된 박테리오신을 dipalmitoyl phosphocholine, dipalmitoyl phosphoethanolamine, dioleoyl phosphocholine 및 콜레스테롤를 각각 4:2:1:4(㏖ ratio)의 비율로 섞은 liposome을 제조하여 최종적으로 pH sensitive bacteriocin-liposome을 제조하였다. 이렇게 제조된 liposome은 pH 4부근에서 대부분 유리되는 것으로 확인되었으나 pH 6이상에서는 일어나지 않았다. 또한 pH sensitive bacteriocin-liposome 한국의 전통 발효식품인 김치에 적용하여 저장시 pH의 저하를 억제시키는 것으로 확인되었다. 본 실험 결과, pH sensitive bacteriocin-liposome은 발효식품의 후산발효 억제에 적용될 수 있으며 추후에 요구르트를 포함한 다른 발효식품에 대한 추가적인 실험이 필요한 것으로 생각되었다.
