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The present study demonstrated the antibacterial effect of photocatalytic oxidation in indoor air using titanium dioxide as the catalyst. Through a series of experiments, it was determined that titanium dioxide did enhance the inactivation rate of the microorganisms under certain conditions. In these experiments the air velocity, relative humidity, and UV (350 nm) intensity were varied. It was found that higher velocities retarded the destruction rate due to the low retention time in the reactor. TiO2 also did not accelerate the reaction at low humidities (30 percent). At a relative humidity of 50 percent, there was complete inactivation of the organisms, but at higher humidities (85 percent), 10 percent of the organisms were still viable. The experiments showed that at higher UV intensities, most of the inactivation was done by the UV photons. However, the photons were not able to completely inactivate the microorganisms. In the photocatalysis experiments there was complete inactivation of the bacteria.

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TiO(2) photocatalysis with ultraviolet (UV-A) light has proven to be a highly effective process for complete inactivation of airborne microbes. However, the overall efficiency of the technology needs to be improved to make it more attractive as a defense against bio-terrorism. The present research investigates the enhancement in the rate of destruction of bacterial spores on metal (aluminum) and fabric (polyester) substrates with metal (silver)-doped titanium dioxide and compares it to conventional photocatalysis (TiO(2) P25/+UV-A) and UV-A photolysis. Bacillus cereus bacterial spores were used as an index to demonstrate the enhanced disinfection efficiency. The results indicate complete inactivation of B. cereus spores with the enhanced photocatalyst. The enhanced spore destruction rate may be attributed to the highly oxidizing radicals generated by the doped TiO(2).

Solar ultraviolet (UV) photocatalyzed oxidation of chemicals with titanium dioxide (TiO2) has received considerable attention. Much less recognized, however, is the ability of the same system to destroy bacteria. This study examined this phenomenon and the conditions that effect it. Bacteria in aqueous solution were given solar exposure with titanium dioxide and their survival with time was detected. Lamps with a predominantly solar ultraviolet spectrum were also used in the experiments. Without exposure to UV light, TiO2 does not affect the bacteria. However, several common bacteria were killed in just a few minutes on solar exposure in the presence of TiO2. Whereas without TiO2 it took more than an hour to destroy them. A concentration of 0.01 percent TiO2 was most effective in killing bacteria and tenfold concentrations lower or higher were successively less effective. Inorganic and organic compounds in solution, even in small amounts, interfered with the efficiency of killing. An alkaline solution also reduced the bactericidal activity. Circulation and agitation provided by stirring to keep the TiO2 particles suspended reduced the time necessary to kill the bacteria. Time-intensity curves for killing bacteria were the same general shape with or without TiO2. This suggests that TiO2 served merely as a catalyst to increase the rate of the reaction but that the mechanism of action was not changed. The shape of the curves shows that the organisms are sensitized with a minimum intensity of radiation and that an increase doesn’t greatly increase the rate of the kill. Below this critical intensity, however, the time required for killing markedly increases as the intensity is decreased.

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The possibility of growing mushroom mycelium in submerged culture was investigated because of the large quantities of low-cost potential growth media available in Florida in the form of citrus press water. The mycelium of Agaricus blazei (M) has been grown in submerged culture on orange juice, citrus press water, and synthetic media. Nutritionally, the mycelium compares favorably with some food sources rich in amino acids and B vitamins. The mycelium, when prepared as a food, lacks the true mushroom flavor; however, because of its bland taste it might be useful for pharmaceutical concentrates of B vitamins and amino acids. The mushroom industry in the United States has grown rapidly since its infancy at the beginning of the 20th century. Although mushrooms themselves have not acquired the popularity in this country that they enjoy in Europe, where they have been eaten for centuries, soups and sauces containing mushrooms are consumed in great quantities.Mushroom propagation as practiced today is an agricultural operation that has changed very little from the process described by Duggar (4) in 1904. In 1948, Humfeld (6) announced a process which offered the promise of large-scale, low-cost production of mushroom mycelium on an industrial basis.