The bacteriostatic and bactericidal actions of vinegar on food-borne pathogenic bacteria including enterohemorrhagic E. coli (EHEC) O157:H7 were examined. The growth of all strains evaluated was inhibited with a 0.1% concentration of acetic acid in the vinegar. This inhibition was generally increased in the presence of sodium chloride or glucose. There was almost no difference in sensitivity to the bacteriostatic action of vinegar among the strains of pathogenic E. coli. Vinegar had a bactericidal effect on food-borne pathogenic bacteria including EHEC O157:H7. This action against EHEC O157:H7 was synergically enhanced by sodium chloride but was attenuated with glucose. For EHEC strains (O157:H7, O26:H11, O111:HNM) the difference in the inactivation rate due to vinegar among strains used was small, although an enteropathogenic E. coli (EPEC) O111:K58:H- strain was more sensitive, being more quickly killed compared with EHEC strains. The inactivation rate due to vinegar was constant irrespective of inoculum size. However, it differed greatly depending on growth phase of the cells, where logarithmic growth phase cells were more sensitive and easily killed than stationary phase cells. The bactericidal activity of vinegar increased with the temperature. Various conditions for bactericidal effects on EHEC O157:H7 were examined by the multiparametric analysis of five factors: acetic acid concentration in the vinegar, sodium chloride concentration, temperature, incubation time, and viable cell number. The combined use of vinegar and sodium chloride, with use of an appropriate treatment temperature, was found to be markedly effective for the prevention of bacterial food poisoning.

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Thirteen strains of rod-shaped lactic acid bacteria, resistant to high concentrations of acetic acid, were isolated from the fermented broth of rice vinegar. These isolates showed homofermentation and differed from all the validly described homofermentative species of the genus Lactobacillus. Although the isolates were divided into two groups on the basis of acid production pattern from carbohydrates and nutritional requirements for growth, all showed extremely high deoxyribonucleic acid homology. The isolates were considered to represent a new species of the genus Lactobacillus. The two groups, based on their biochemical and physiological properties, were treated as biovar I and biovar II. A new species proposed for these isolates was named Lactobacillus acetotolerans. The type strain of L. acetotolerans sp. nov. is NBI 3014 (= JCM 3825).Acetic acid bacteria are usually the only bacteria that can grow in fermenting vinegar broth, which ordinarily contains more than 2 to 3% acetic acid. However, on rare occasions, lactic acid bacteria tolerant to acetic acid grow in the fermenting vinegar broth and cause turbidity in the broth (5). During a study of microorganisms in vinegar production, lactic acid bacteria that showed an unusually high tolerance to acetic acid were isolated from the turbid broth of rice vinegar and were thought to represent a new taxon of lactic acid bacteria.The present study deals with the characterization of these isolates and a description of their taxonomic status. The results indicate that they can be regarded as a new species for which the name Lactobacillus acetotolerans is proposed. MATERIALS AND METHODSBacterial strains. Thirteen strains (Table 1) were isolated from fermented rice vinegar broth which had turned turbid. Nakagawa medium (Asahi Breweries Ltd., Tokyo, Japan), useful for selection of lactic acid bacteria (20), supplemented with 1% agar (5) was used for the isolation of the bacteria. A number of other Lactobacillus species were examined for comparison (Table 1) Cultivation media. Unless otherwise stated, the bacteria were cultivated on Briggs liver broth (pH 5.0) (16) at 30°C. The authentic strains, except for L . homohiochii ATCC 15434*, were cultivated on Briggs liver broth (pH 6.8) at 30°C. For L . homohiochii ATCC 15434*, Briggs liver broth was supplemented with 10 c1. g of DL-mevalonic acid lactone per ml and 7% (voVvol) ethanol (pH 5.0). L . catenaforme JCM 1121T was cultivated anaerobically in a GasPak jar (BBL Microbiology Systems, Cockeysville, Md.). For solid media, 1.5% agar was added to the above liquid media.Morphology of the isolates. Cell shape, cell size, cell arrangement, and Gram stain were observed for cells grown in Briggs liver broth (pH 5.0) after 3 to 5 days at 30°C. The * Corresponding author. cells were also observed with a JEOL scanning electron microscope (model JSM-T20). The modification of Hucker and Conn was used for the Gram stain (8). The motility of the cells cultured on a Briggs agar plate (pH 5.0) (1) was tested after 3 to 21 days at 25 a...

Xanthomonas campestris K-11151, isolated from soil, produced a periplasmic alpha-amylase of a new type. The enzyme was purified to homogeneity, as shown by several criteria. The purified enzyme showed almost the same activities on alpha-, beta-, and gamma-cyclodextrins, soluble starch, and amylose. Moreover, it was active on branched cyclodextrins, pullulan, and maltose but not on glycogen. Kinetic analysis showed that alpha-cyclodextrin was the best substrate among the cyclodextrins. The substrate specificity suggested that this enzyme had the combined activities of alpha-amylase, cyclodextrinase, and neopullulanase.