Inactivation of Bacillus Subtilis Spores by GaseousOzone

摘要

This study was conducted to determine the proper operationalrnconditions for ozone gas to effectively inactivate Bacillus subtilis, arnspore forming non-pathogenic bacteria that belong to the genusrnBacillus and share the same physiological characteristics as Bacillusrnanthracis that cause the infectious anthrax disease.rnThe main objective was to determine the ozone concentration andrncontact time required to produce desired levels of inactivation ofrnbacterial spores. The data gathered in this research included the effectrnof air humidity, temperature and the level of hydration of spores on therninactivation rate of the spores. In addition, the ozone demand ofrndifferent type of material surfaces was determined together with thernassessment of the physical damage on the material.rnBacillus Subtilis sp. Was obtained from the Microbiology Laboratoriesrnof the Biology Department of SDSU. The strain was grown in TrypticrnSoy Broth (TSB) for at least one week to allow sporulation. The culturernin the form of vegetative cells and spores was harvested and heatrnshocked at 65°C and further treated with lysozyme to completelyrneliminate vegetative cells. The spread plate method was used torndetermine the number of the spores in solution. Spores were exposed tornozone on strips of different material (glass, carpet, wood, plastics,rnplaster, ceramic, vinyl floor, and paper). A 50 μL amount of sporernsolution (about 108 spores/mL) was placed on each strip.rnThe ozonation chamber was manufactured for this study by Pure-Otechrnof Escondido, California. The system has its own Pure-O-Techrnozone generator and Sequal oxygen concentrator (See ExperimentalrnSet-up). After ozone concentration, humidity level and temperaturernwere stabilized at the desired values, the test strips were put into thernchamber and exposed to ozone. Duplicate samples were removed at