The colonial growth of Bacillus subtilis vegetative and spore cells was evaluated by determining the time course of the growth heat changes (growth thermogram) with a microbial calorimeter. The actual heat evolution curve (f (t) curve) obtained from the thermogram was in good agreement with the viable cell number changes. From the logarithmic f (t) curve, the exponential growth phase was estimated to be the period of between 31 and 35 h after inoculation and the growth rate constant (μ') was 0.36 h-1. The f (t) curve was also obtained from the thermogram of the spore cells. The starting time of growth of the spore cells was 9 h later than that of the vegetative cells. This period corresponded to the germination period. The growth profile after germination was almost similar to that of the vegetative cells. The suppressive activities of sucrose monopalmitate (SMP) against the vegetative and spore cells were evaluated by the f (t) curves. Our results show that SMP inhibited metabolic inductions during the lag phase of the vegetative cells and the germination of the spore cells. Microbial calorimetry is a method suitable for non-destructive growth measurements of microbial colonies on the surface of a solid medium.
A small-sized generator of ozonated water was developed using an electro-conductive diamond. We studied the optimum conditions for producing ozonated water. As a result, we developed a small-sized generator of ozonated water driven by a dry-cell for use in the average household. This generator was easily able to produce ozonated water with an ozone concentration (over 4 mg/L) sufficient for disinfection. In addition, we verified the high disinfecting performance of the water produced in an actual hospital.
Eight salt-tolerant yeasts were isolated from contaminated pickled plums which were seasoned with honey and “Umami” seasoning. They were classified into four main groups according to random amplified polymorphic DNA analysis, and three of ten kinds of food additives tested inhibited their growth. The type strains of each group were identified as Zygosaccharomyces bisporus, Pichia subpelliculosa, and two strains of Candida apicola based on the D1/D2 region sequence of the 26S rRNA gene. They were able to grow in medium containing 6% (w/v) NaCI. A number of yeasts were isolated from production lines by the swab method, but not from the salted plums used as raw materials. These results show that the production lines require washing with antimicrobial agents effective against salttolerant yeasts. Three commercial food additives, San-keeper 381, Sunsoft No.700P-2, and potassium sorbate inhibited the growth of Z. bisporus at 125 to 250 μg/ml. In particular, Sankeeper 381 altered the morphology of this species at 125 μg/ml. C. apicola and P. subpelliculosa were inhibited by Sunsoft No.700P-2 and potassium sorbate at 250 μg/ml. These results indicate that the washing of production lines with disinfectant and the use of food additives that effectively prevent salt-tolerant yeast contamination are necessary.
The effect of the heating conditions of dolomite powder on its antiviral activity was studied against the H5N3 avian influenza virus. Calcium oxide (CaO) and magnesium oxide (MgO), obtained by the thermal decomposition of dolomite above 800°C, were shown to have strong antiviral activity, but the effect was lessened when the heating temperature exceeded 1400°C. Simultaneous measurement of the crystallite size suggested that the weakening of the activity was due to the considerable grain growth of the oxides. It was found that the presence of Mg in dolomite contributed to the deterrence of grain growth of the oxides during the heating process. Although both CaO and MgO exhibited strong antiviral activity, CaO had the stronger activity but quickly hydrated in the presence of water. On the other hand, the hydration of MgO took place gradually under the same conditions. Separate measurements using MgO and Mg (OH) 2 revealed that MgO had a higher antiviral effect than Mg (OH) 2. From the overall experiments, it was suggested that the strong antiviral activity of dolomite was related to the hydration reaction of CaO.
Pathogenic Yersinia enterocolitica serotypes 0: 3, 0: 5, 27, 0: 8 and 0: 9 were inoculated into sliced and ground pork, and the samples were stored under vacuum or aerobic conditions at 2 and 7°C. All serotypes survived for 5 weeks in pork with or without vacuum packing without any discernable increases in their population. In sterilized pork with or without vacuum packing, there was no evident growth of Y. enterocolitica. In pork broth in which the pH had been artificially adjusted to 6.8, the growth of Y. enterocolitica was faster than that at 5.7. It is suggested that the growth of Y. enterocolitica in pork with or. without vacuum packing may be inhibited by pH but not by the microflora or lactic acid bacteria in pork.