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UV Light Microbial Inactivation in Foods
Published in Tatiana Koutchma, Ultraviolet Light in Food Technology, 2019
As shown in Figure 4.2, nucleic acid absorbs UV light from 200 to 300 nm. UV light inactivates microorganisms by disrupting their DNA or RNA structures by inducing six types of damages. The primary mechanism of inactivation by UV is the creation of pyrimidine dimers (Figure 4.1), which are bonds formed between adjacent pairs of thymine or cytosine pyrimidines on the same DNA or RNA strand. Dimers prevent microorganisms from replicating, thereby rendering them inactive and unable to cause infection. Figure 4.2 shows the relationship between the ability of UV light to destroy bacterial cells and the ability of this cell’s nucleic acid to absorb UV light. The germicidal lamp emitting UV at 254nm is operating very close to the optimized wavelength for maximum absorption by nucleic acids at around of 260 nm.
Microbial Growth and Its Control
Published in Maria Csuros, Csaba Csuros, Klara Ver, Microbiological Examination of Water and Wastewater, 2018
Maria Csuros, Csaba Csuros, Klara Ver
Nonionizing radiation has a wavelength longer than that of ionizing radiation, usually greater than about 1 nm. A good example for nonionizing radiation is ultraviolet (UV) light. UV light damages the DNA of exposed cells. The UV wavelength most effective for killing microorganisms is about 260 nm; these wavelengths are specifically absorbed by cellular DNA. UV radiation is also used to control microbes in the air. A UV or germicidal lamp is commonly found in hospital rooms, nurseries, operating rooms, and cafeterias. A potential problem is that UV light can damage the eyes, and prolonged exposure to UV light can cause burns and skin cancer. Sunlight contains some UV light, but the most effective wavelengths are screened out by the atmosphere.
Physical and photocatalytic properties of Nd codoped (Ag, Cu)TiO2 thin films
Published in Surface Engineering, 2021
A. Mustafa, M. Bououdina, B. Al-Najar, T. Souier, F. Bensouici, B. Belache
The photocatalytic activity experiments were carried out in a cylindrical glass reactor containing 4 films with a total area equal to 12 cm2 acting as a catalyst and immersed in 35 ml of an aqueous solution of Methylene blue (MB) at 2.5 × 10−5 M concentration. A 15W G15T8 Philips germicidal lamp was used as a UV source, emitting UVC monochromatic light with a wavelength of 254 nm. The lamp is placed horizontally above the cell and at a distance of 7 cm from the cylindrical glass.