The bactericidal actions of a novel bis-QAC, 4, 4'-(1, 6-hexamethylenedithio) bis (1-octylpyridinium iodide) (4DTBP-6, 8) against the vegetative cells and the spores of Bacillus subtilis ATCC6633 were investigated. The bactericidal activity (log MBC-1) did not change in the temperature range of 10-50°C, the pH range of 5.0-9.0 and the contact time over 5min but remarkably depended on the initial cell concentration and the recovery medium. It was found that lecithin contributed to the recovery of the injured bacteria besides inactivating 4DTBP-6, 8 whereas Tween 80 had no effect. Furthermore, 4DTBP-6, 8 exhibited a strong inhibition against the germination and the outgrowth of spores. On the other hand, the kinetics analysis of the bactericidal action revealed that the initial death rate constant (k) for the vegetative cells was much higher than that for the spores. However, the initial death rate constant for the vegetative cells was dependent on both the temperature and pH while this was not the case for the spores. The activation energy (Ea) for the vegetative cells rapidly decreased with the increasing concentration of 4DTBP-6, 8, and the value of Ea (1.97kJ/mol) at the concentration of 9 μM was similar to that (2.10kJ/mol) for the spores at the concentration of 100 μM. The difference the concentration exponent (n) between the vegetative cells and the spores was observed, such as n≅1 for the vegetative cells and n<0.2 for the spores at low temperatures. These results indicate that the spores are much more resistant to 4DTBP-6, 8 than the vegetative cells and suggest that the kinetics of the bactericidal action of 4DTBP-6, 8 against the vegetative cells and the spores are different.
The kinetics of the desorption of bovine serum albumin (BSA) from stainless steel particles at various surface coverage values (θ) or at various cleaning temperatures were studied in a plug-flow column fed by a 0.1 M NaOH solution.The desorption curves obtained by plotting the logarithm of the amount of residual BSA against cleaning time was analyzed by using an integrated model for two first-order processes occurring simultaneously.At each θ or temperature, the curve of BSA desorption could be successfully reduced to the sum of two independent and simultaneous first-order processes occurring at different rates.The desorption rate constant (kf) for the faster-desorbing BSA (BSAf) was influenced by θ, especially above 0.6.On the other hand, the rate constant (ks) for the slower-desorbing BSA (BSAs) was nearly constant when θ was above 0.6.The ks was approximately 10 to 20 times lower than kf.The Kf showed an Arrhenius-type temperature dependence.The apparent activation energy (Ea) of kf was estimated to be 33kJ/mol.The kf increased by approximately 1.4 times for every 10°C rise in temperature.The proportion of BSAs to the total amount of adsorbed BSA decreased with increasing cleaning temperatures.
The effectiveness of a copper-alcohol treatment to reduce the microbial numbers in the powdered crude drugs was investigated. Furthermore, the effect on the chemical quality control was also evaluated. After the treatment, no microorganisms and no changes in the appearance of the crude drugs were found. Furthermore, no remarkable change in the contents of index components in the powdered crude drugs was found except for that of swertiamarin and gentiopicroside in gentian and that of ginsenoside Rb1 and Rg1 in ginseng. These results suggest that this treatment method would be very useful to reduce the number of microorganisms in powdered crude drugs.
The death of Escherichia coil in magnesium oxide (MgO) powder slurry was found to follow first-order reaction kinetics. The value of the apparent death rate constant (k) increased with the powder slurry concentration and the slurry temperature. The bactericidal action of the MgO powder slurry was greater than that of a NaOH solution of an identical pH. E. coil grown at lower temperatures (TG) became more sensitive to MgO. The Arrhenius plots of k for E. coil grown at 27, 37 and 45°C exhibited discontinuous points (Td) at approximately 13, 21 and 29°C, respectively, and the differences, TG-Td, were observed to be almost constant (14-16°C)
We investigated the antibacterial effect of commercial grapefruit seed extract (GSE, Liquid), which has recently been attracting attention as a food additive, on Legionella pneumophila. The sensitivity test was performed using the disc method. All 25 strains tested were sensitive to GSE, and formed clear inhibition zones in its presence. The minimum inhibitory concentration (MIC) values were measured by the agar dilution method. The MIC of GSE in the strains was in the range of 98mg/l to 390mg/l, and the MIC90 was 390mg/l. The minimum bactericidal concentration (MBC) values for the test strains were also determined. MBC90 was 50, 000, 6, 300, and 3, 100mg/l when the exposure time was 1, 10, and 60 minutes, respectively. These bactericidal test results demonstrate that GSE has a bactericidal effect on L. pneumophila.