Lactic acid bacteria exhibiting activity against the gram-positive bacterium Bacillus subtilis were isolated from rice bran. One of the isolates, identified as Enterococcus faecalis RJ-11, exhibited a wide spectrum of growth inhibition with various gram-positive bacteria. A bacteriocin purified from culture fluid, designated enterocin RJ-11, was heat stable and was not sensitive to acid and alkaline conditions, but it was sensitive to several proteolytic enzymes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that enterocin RJ-11 had a molecular weight of 5,000 in its monomeric form. The amino acid sequence determined for purified enterocin RJ-11 exhibited high levels of similarity to the sequences of enterocins produced by Enterococcus faecium.Lactic acid bacteria (LAB) are widely used as starter cultures for dairy, meat, and vegetable fermentations (24, 38). Some LAB strains are known to produce various types of bacteriocins, which have bactericidal effects against gram-positive bacteria, including food-borne pathogens (17,22,23,32). This beneficial trait has led to utilization of bacteriocins as food additives (9, 30). For example, nisin, a bacteriocin produced by Lactococcus lactis, has been used for food preservation in a large number of countries (7,15).Fermented soybean paste (miso) is a traditional food seasoning in Japan. Miso has been assumed to contribute to the health and lifespan of Japanese due to its favorable physiological effects, such as its antioxidative activity (3), its antimutagenic effect (18,21,29,39), and its inhibitory effect on accumulation of cholesterol (1, 2). In the first step of the miso production process, called koji mold fermentation, a koji mold (Aspergillus oryzae) is grown on steam-cooked rice. During this process care must be taken to avoid contamination by sporeforming bacteria, such as Bacillus subtilis, since the conditions are favorable for growth of bacteria.We previously tried to use LAB strains with antibacterial activity in the koji mold fermentation process to suppress the growth of contaminating bacteria. However, a preliminary test revealed that most LAB strains that are used industrially do not grow well on cooked rice. This poor growth may be ascribed to a deficiency of nutrients in rice, which are required by the LAB strains tested. In addition, the fairly low water activity of cooked rice seems to be unfavorable for the growth of LAB strains. We also attempted to isolate LAB strains which grow well on cooked rice and have an inhibitory effect on the growth of vegetative cells of B. subtilis, which is known to often contaminate preparations because of its spore-forming capacity. A large number of lots of rice bran were collected and used for screening LAB strains, since isolated strains are expected to grow well on steam-cooked rice. We found that rice bran is a good source for isolation of LAB strains that produce bacteriocins. In this paper, we describe purification and characterization of a bacteriocin produced by one of the iso...

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A temperature-sensitive osmophilic mutant of Zygosaccharomyces rouxii, OS15, was isolated, which required high salt or sugar concentration for growth above 30°C. Cell viability at 35"C in the presence of NaC1 was higher than in the absence of NaCI, and a survival ratio of the mutant cells after incubation at 55"C was also higher in the presence of NaCI than NaCl-free condition. Furthermore, resistance to UV light, hygromycin B and geneticin was improved in the presence of NaC1. There was no difference between the parent and the mutant in fatty acid saturation and microscopic cell shape under NaCI condition.