In 1994, a new bacteriocin, enterocin AS-48, produced by Enterococcus faecalis subsp. liquefaciens S-48, with a cyclic structure arising from a head-to-tail linkage was first discovered. After that, seven research papers concerning cyclic bacteriocins have been presented. In 2003, a new classification system of bacteriocins in which the cyclic bacteriocins are “class V” was proposed. Structural and genetic characteristics and antimicrobial mechanisms are different among the class V bacteriocins, but all of them have high stability against heat and pH and high antimicrobial activity. At present, researches on mechanism of their enzymatic cyclizations which give them their high stability and bioactivity are taking place, and novel utilization of these cyclic bacteriocins in the future is expected.

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We have been engaged in the development of a novel fermented food from wheat flour “fermented instant Chinese noodl” using lactic acid bacterial fermentation. A few fermented foods from wheat flour using lactic acid bacterial fermentation are known. The only well known products are sourdough breads. Since the pH value of the noodle environment is alkaline with kansui (around 8.5), alkaline tolerance is required for the lactic acid bacteria to ferment noodle dough. The screening of the lactic acid bacterial strains suitable for the fermentation was conducted using 46 strains from 12 species (including subspecies)of lactobacilli isolated mostly from plant-materials. Positive results were obtained only with Lactobacillus (Lb.) pentosus and Lb. plantarum strains. The fermented instant Chinese noodle prepared by the bestselected strain, Lb. plantarum NRIC 0380, showed improved noodle texture with a light sour taste. The relationship between the food chemical characteristics of the noodle dough and physiological characteristics of lactobacilli are also discussed.

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In a previous study conducted in our laboratory, we performed a survey on the distribution of lactic acid bacteria (LAB) during the fermentation process of fermented black beans (dochi). In this study,31 dochi samples were collected from markets and analyzed for LAB. Twenty-three acidproducing bacteria were isolated from marketed dochi samples. These isolates were subsequently divided into classes by phenotypes of restriction fragment length polymorphisms of 16S ribosomal DNA. Phenotypic and biochemical characteristics revealed that the LAB collected belonged to six bacterial groups (A-F), most of which were homofermentative.Enterococcus faecium was the most abundant of the dochi-isolated LAB, as was previously found in the dochi fermentation process. These results suggest that Ent. faecium is the main LAB present in marketed dochi. Furthermore, the antibacterial activities of isolates were determined and two isolates showed antibacterial activities against the indicator strain Lactobacillus sakei JCM 1157^T.

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