In order to develop a natural food preservative, the root bark of Morus alba was extracted with several solvents, and then antimicrobial activity was investigated. The optimum extracting condition for the antimicrobial substance from the sample, minimum inhibitory concentration (MIC) of the extracted substance against microorganisms were also examined. The antimicrobial activity of the ethanol extract from the sample was atronger than those of the extracts by the other solvents such as water, methanol, ethyl acetate and acetone. The optimum extracting condition for antimicrobial substance from the sample was shaking extraction twice for 5 hours at room temperature in case of 7 times of absolute ethanol added to the crushed root bark of Morus albs. The ethanol extract from the root bark of Mores albs had strong antimicrobial activity against Gram positive bacteria(MIC, 6.4-19.2 g/ml) such as B. subtilis, B. cereus, L. monocytogenes and S. aureus. Especially, Bacillus species was the most susceptible to the extracted substance. The ethanol extract showed antimicrobial activity against Gram negative bacteria(MIC, 160-1600 g/ml) and yeasts(MIC, 1600 g/ml) such as C. albicans and S. acidifaeciens. The extract also showed growth inhibition against molds such as A. niger, A. parasiticus, A. versicolar and T. uiride.

Bacteriocins from lactic acid bacteria have attracted much attention in recent years because of their useful worth in increasing safety and extending shelf life of foods. These substances show an inhibitory effect against some food spoilage bacteria and food-borne pathogens. The inhibitory effect of the bacteriocin produced by lactic acid bacteria against Listeria monocytogenes(L. monocytogenes) was examined in this study. The culture supernatants of 5 kinds of bacteria among the 10 kinds of tested lactic acid bacteria had the inhibitory activity against Listeria sp., various Gram positive and Gram negative bacteria. Bacteriocin produced by Lactobacillus plantarum(Lact. plantarum) LMG 7945 was the most active toward L. monocytogenes. Bacteriocin production of the Lact, plantarum LMG 7945 cultured on MRS broth was increased late logarithmic phase over early stationary phase. This bacteriocin was stable at heat treatment and acidic pH relatively; The activity was retained after heating at 121 for 15min and was active in the pH range of 2-4 but was lost above pH 5.

The antibacterial and antifungal effect of grapefruit seed extract(GFSE) was investigated for its purpose of application to a diverse spectrum of field as sanitizers, disinfectants and preservatives. GFSE showed comparatively high content of such flavoniods as naringin and hesperidin and ascorbic acid. GFSE containing a low level of organic acids is a heavy viscous and water-soluble liquid. As a result of the antimicrobial test of GFSE, Bacillus subtilis and Aspergillus oryzae did not survive at detectable levels when treated with more than 100 ppm of GFSE. The minimum inhibitory concentrations of GFSE for a wide variety of pathogenic and putrefactive bacteria, fungi and yeasts were 100 ppm and 250 ppm, respectively. In the comparable electron micrograph of microbial cells treated with GFSE or not, we could conclude that GFSE destroy microorganisms by disrupting the functions of the cell wall membrane and microbial spores.

The effect of the ethanol extract from salviae miltiorrhizae radix (Salvia miltiorrhiza) on the microbial growth and the stability of the extracted antimicrobial material were investigated. The ethanol extract had strong growth inhibition activity (MIC, 3.13-50.0 pg/ml) against Gram-positive bacteria such as B. subtilis, L. monocytogenes and S. aureus. Among Gram-positive bacteria tested, B. subtilis was the most susceptible to the extracted substance. While the antimicrobial activity of the ethanol extract was weak (MIC, 400-800 ug/ml) to E. coli and yeasts (C. albicans. Sacch. diastaticus). The ethanol extract had bactericidal action at higher concentration than MIC against B. subtilis, while the extract had only bacteriostatic action against S. aureus. The extracted antimicrobial substance was stable in the pH range of 4.0 to 10.0, heat treatment at 121℃ for 15 min, and freezing and thawing

본(本) 실험(實驗)은 Lactobacillus bulgaricus의 우유 배지(培地)에서 항균물질(抗菌物質)을 추출(抽出) 및 정제(精製)하여 항균효과(抗菌效果)를 조사(調査)하였으며 그 결과(結果)를 요약(要約)하면 다음과 같다. 칼처의 항균물질(抗菌物質)을 methanol-acetone으로 추출(抽出)하고 Sephadex G-50 gel filteration 그리고 thin layer chromatography로 정제(精製)하였다. 칼처의 산중화려액(酸中和濾液)이 탁도법(濁度法)에 의하여 Bacillus subitilis의 발육(發育)을 억제(抑制)하였으므로 산(酸)외에서 항균물질(抗菌物質)이 있음을 확인할 수 있었다. 정제(精製)된 항균물질(抗菌物質)은 Bacillus subtilis, Escherichia coli, Pseudomonas fluorescens, Staphylococcus aureus, Proteus vulgaris 및 Shigella dysenteriae의 발육(發育)을 억제(抑制)하였다. Thin layer chromatography로 정제(精製)한 항균물질(抗菌物質)은 항균작용(抗菌作用)을 나타내는 나 유산(乳酸)을 함유하지 않는 것이다.

Imidazole계(系) 농약(農藥)인 prochloraz와 triazole계(系)인 triadimefon의 사과나무 부란병균(腐爛病菌)(Valsa ceratosperma)에 대한 항균력(抗菌力) 및 지방산(脂肪酸)의 조성변화(組成變化)에 미치는 영향(影響)을 조사(調査)한 결과(結果)는 다음과 같다. 균(菌)이 생육(生育)하고 있는 PS액체배지(液體培地)에 두 약제(藥劑)를 각각(各各) 처리(處理)하였을 때의 값은 prochloraz의 경우는 1~5ppm이었고 triadimelon은 5~10ppm이었으며 prochloraz의 저해능(沮害能)이 다소 높았다. 균사(菌絲)의 현미경(顯微鏡) 관찰결과(觀察結果) 약제(藥劑) 처리구(處理區)에서는 모두 균사(菌絲)의 이상생육현상(異常生育現象)이 관찰(觀察)되었다. 균체(菌體)에 약제(藥劑)를 처리(處理)함으로 인해서 지질(脂質)의 변화(變化)를 조사(調査)한 결과(結果) 균체중(菌體中)의 총지질(總脂質) 및 지방산(脂肪酸)의 함량변화(含量變化)는 없는 것으로 나타났다.