Twenty-five yellow chromogenic strains isolated from hospital tap water samples collected nationwide were identified by partial 16S rDNA sequencing. In addition, the chlorine resistance of the isolates was experimentally investigated. The results showed that of the strains tested, 12 strains (48.0%) were Sphingomonas ursinco/ainatatoria, which was most frequently identified, followed by 2 strains (8.0%) of Mycobacterium frederiksbergense and 1 strain (4.0%) each of Sphingomonas adhaesiva, Sphingopyxis witfiariensis and Porphyrobacter donghaensis. The other strains were not identified clearly but they belonged to the order of Alphaproteobacteria. On the other hand, the identification results by sequencing and biochemical property testing were not consistent in any of the strains, showing that it was difficult to accurately identify the yellow chromogenic bacteria in tap water based on only their biochemical properties. When the 25 isolates were exposed to 0.1 mg/I residual free chlorine for 1 minute, 22 isolates (88.0%) survived. When the CT (Concentration Time) value killing 99.99% of the bacteria was investigated in 6 of these survivors, M. frederiksbergense (Y-1 strain) was most resistant to chlorine with the CT value of 32 mg·min/l, followed by S. ursincola/natatorla (Y-7 strain) with the CT value of 3.3 mg·min/l. The CT values of Y-5 (Sphingomonas sp.), Y-27 (S. ursincola/natatoria) and Y-21 (Asticacaulis sp.) were within the range of 0.9-0.1 mg·min/l. Of the 6 strains, S. adhaesiva (Y-10) showed the weakest resistance with the CT value of 0.03 mg·min/l. It was clarified that most yellow chromogenic bacteria isolated from hospital tap water were Sphingomonas spp., and these bacteria were experimentally resistant to chlorine.
Disposal of the seaweed wakame (Undaria pinnatifida) by inoculating the halotolerant bacterium Bacillus sp. HR6 was examined in an experimental scale composting system. Strain HR6 was effective in initiating the composting process of wakame, and there was a rapid increase in temperature to over 54.9-55.7°C after 18-20 h. The composting process of wakame could be carried out despite a high NaCI content, 28.2 mg/g, although lower salinity resulted in a shorter lag time and higher weight reduction. In a larger scale composting process with aeration, two peaks of temperature change were found which corresponded well to oxygen consumption and CO2 emission during the process. The pH increased to 8.83 and organic materials were reduced to 93.4 % after 72 h. The initial N and C contents were 3.9 and 34.%, respectively, both of which decreased during the composting process. The changes in the viable cell numbers suggested that strain HR6 predominated before 24 h and other microorganisms including HR6 were present in a mixed state during the later period of composting. The total content of alginate (TA), 32.2 % in the initial stage, decreased to 29.2 after 72 h, while water soluble alginate (WSA) increased, indicating that the solubilization and decomposition of alginate had occurred during the composting process.
We evaluated bronopol as a practical alternative anti-fungal agent to malachite green for use in hatcheries. Repeated exposure everyday, just after fertilization to the stage of eggs showing eye development to 50 mg/L and 100 mg/L bronopol for 30 min showed an efficacy comparable to 0 mg/L (control) for the inhibition of fungal infection in rainbow trout (Oncorhynchus mykiss) eggs. The 100 mg/L bronopol treatment groups showed a control of fungal infection up to the stage of eye development in eggs. Significant differences in terms of the number of eggs showing eye development were seen between 0mg/L and treatment at 50 and 100 mg/L bronopol
A pulsed power supply was used to generate a corona discharge on a polyethyleneterephthalate bottle, to conduct plasma sterilization at atmospheric pressure. Before generating such a discharge, minute quantities of water were attached to the inner surface of the bottle and to the surface of a high voltage (HV) electrode inserted into the bottle. Next, highvoltage pulses of electricity were discharged between electrodes for 6.0s, while rotating the bottle. The resulting spore log reduction values of Bacillus subtilis and Aspergillus niger on the inner surface of the bottle were 5.5 and 6 or higher, respectively, and those on the HV electrode surface were each 6 or higher for both strains. The presence of the by-products gaseous ozone, hydrogen peroxide, and nitric ions resulting from the electrical discharge was confirmed.
To investigate effective methods to sterilize a biological safety cabinet contaminated with Bacillus spores, a sterilization study was performed using the vaporized KMT reagent. Five kinds of test carriers inoculated with Bacillus subtilis spores, which had been prepared inhouse, were used as indicators. The KMT reagent was placed in the middle of the work-area (1.2 m-wide, Class II type A cabinet). Approximately 300 ml of vaporized KMT reagent could bring about complete sterilization of this cabinet by 24 h of exposure without severe corrosion. Vaporized KMT reagent could be used for the safe and easy sterilization of cabinets contaminated with Bacillus spores.
Natural shelf life extending agents and sugar fatty acid esters that might inhibit the growth of B. subtilis IAM 1026 were screened, and the effective agents were as follows: β-thujaplicin (Hinokitiol) and chitosan, inhibited the growth of IAM 1026 at a concentration of 0.001% ; ε-polylysine and M-1695 (a sugar fatty acid ester) at 0.005%; citrus seed extract, thiamin lauryl sulfate, and grapefruit seed extract at 0.01%; CT-1695 and L-1695 (sugar fatty acid esters) at 0.05%; pectin digests and SM-800 (a sugar fatty acid ester) at 0.5%; water pepper seed extract and the sugar fatty acid esters SM-1000 and CE-1695 at 1.0%. The growth inhibitory effects of the agents in custard cream were not necessarily similar to those in liquid culture. The agent that showed the highest inhibitory effect in custard cream was 0.3% β-thujaplicin, followed by 0.3% ε-polylysine.
A biological indicator (BI) is a useful product to confirm sterility assurance after a sterilization procedure. In ISO 11138 and 14161, the concrete procedures regarding the use of BI are described for BI manufacturers and users, respectively. There are several problems involving BI use which must be addressed. These include population verification, D value verification and the general misuse of BI and so on. In this paper, the author will present concrete examples of the above situations and describe how to deal with these problems.