Airborne bacterial spores inactivation with UV radiation over TiO2 coated glass rings.

ZACARÍAS, S. M.; VISUARA, M. E.; ALFANO, O. M.; SATUF, M. L.

Buenos Aires

Simposio; 5 Simposio Internacional de Biotecnología e Ingeniería Ambiental (5ISEBE); 2016

Universidad Nacional de San Martín, CONICET

Bioaerosols containing viruses, bacteria, and fungi can be responsible for infectious diseases, toxic reactions, and allergic responses. Therefore, research on disinfection technologies to control bioaerosols in air constitutes an area of great scientific interest. Heterogeneous photocatalysis is a potential alternative to mitigate the problem of air contamination indoors, mainly to inactivate resistant forms of microorganisms such as bacterial spores. In this study, the photocatalytic inactivation of Bacillus subtilis (strain ATCC 6633) spores over TiO2-coated rings is evaluated. Borosilicate glass rings (5 mm diam × 10 mm length) were coated with 1, 2 and 3 layers of TiO2 P-25 (Evonik) by the ?dip-coating? technique. The coated rings were nebulized with a suspension of spores employing a 6 jet "Collison" type nebulizer (BGI Instruments), and then exposed to UV-A radiation for 12 hours. UV lamps of different irradiation power were employed in separate assays. Bacterial inactivation was followed by analyzing the concentration of viable bacteria every 4 hours. Experimental results were fitted with the exponential equation N=N0 exp(-kt), where N (CFU cm-2) is the concentration of viable bacteria per unit area of support, N0 (CFU cm-2) is the initial bacterial concentration, k (h-1) is the apparent kinetic inactivation constant, and t (h) is the irradiation time. CFU stands for colony forming units.After 12 h of irradiation significant reduction of the spores? viability was observed along the treatment. An increase in the UV-A irradiance or in the TiO2 content increases the absorption of energy by the catalyst and, therefore, the availability of reactive oxygen species able to damage the spores structure. It is worth noting that the spores? viability over glass rings without catalyst showed no changes in the presence of UV-A radiation.