초록
Lactobacillus spp.같은 유산균은 탄수화물을 발효하여 ATP를 생성하며, 시판되는 요구르트 생산에 이용되고 있다. Lactobacillus spp.는 장관계 건강에 유익한 균으로, 특히 Lactobacillus acidophilus를 함유하는 요구르트는 대장암 초기단계를 예방하는 효과가 있는 것으로 나타나 관심이 모아지고 있다. 본 연구에서는 고형 요구르트와 액상 요구르트, 그리고 Lactobacillus acidophilus 세 그룹의 유산균을 배양하였다. 먼저 Lactobacillus spp.의 최적의 배양조건을 조사하였고 세 그룹의 생장능과 젖산생성을 비교하기 위해 혼탁도와 pH를 측정하였다. 배양 상층액의 젖산을 비교하기 위해 HPLC를 시행하였으며 Staphylococcus aureus와 Escherichia coli에 대한 항균력을 측정하였다. Lactobacillus spp.의 최적의 배양조건은 $25^{\circ}C$의 온도로 MRS배지에서 24시간 배양이었다. 혼탁도와 젖산 생성은 L. acidophilus가 가장 높았고 액상 요구르트, 고형 요구르트 순으로 나타났다. Paper disk법을 이용한 항균력 시험에서는 S. aureus에 대해서는 세 그룹 모두 항균력이 없었으며 E. coli에 대해서는 L. acidophilus에서 1.8 mm의 억제대를 보였다. 이 연구결과로 L. acidophilus는 높은 젖산 생성 능력과 항균력을 가지고 있음을 확인하였다.
Lactic acid-producing bacteria such as Lactobacillus spp. function to ferment carbohydrates and produce ATP. Such Lactobacillus spp. are used for the production of commercial yogurts. Lactobacillus spp. are beneficial to the intestinal tract, and Lactobacillus acidophilus-containing yogurts have received considerable attention because of their preventive effects against early-stage cancer of the large intestine. In this study, lactic acid-producing bacteria were cultured from three different groups: commercial solid yogurt (for eating), commercial liquid yogurt (for drinking), and Lactobacillus acidophilus-containing yogurt. We first determined the optimum culture conditions for Lactobacillus spp. and then analyzed turbidity and pH in order to compare the growth abilities and lactic acid-production capacities among the groups. Finally, high-performance liquid chromatography was used to measure the lactic acid content in the culture supernatants, and the antibacterial activities against Staphylococcus aureus and Escherichia coli were compared among the three groups. The optimum culture conditions for Lactobacillus spp. were MRS medium at $25^{\circ}C$, for 24 h. The highest turbidity was found in L. acidophilus-containing yogurt, followed by liquid yogurt and solid yogurt. Similarly, the highest lactic acid production ability was found in L. acidophilus-containing yogurt, followed by liquid yogurt and solid yogurt. Culture supernatants from the three groups did not show any antibacterial activity towards S. aureus; however, supernatants derived from L. acidophilus-containing yogurt resulted in a 1.8 mm inhibitory zone against E. coli in a paper disk diffusion test. These results revealed the high level of lactic acid-production capacity and antibacterial activity in L. acidophilus-containing yogurt.
