Photocatalytic inactivation of dairy bacteriophages contained in aerosol: Comparative evaluation of efficiencies

Abstract

The aim of this work was to investigate the photocatalytic inactivation efficiencies of eight phages infective to lactic acid bacteria (LAB) contained in bioaerosols. Studies were performed in a semi-pilot scale equipment, which consists of a stainless steel camera, in which air containing the phage particles circulates, and an acrylic reactor with twenty UV-A lamps and six borosilicate plates covered with the catalytic film (TiO2). Phages (ALQ13.2, ATCC 15807-B1, ATCC 8014-B1, BYM, CHD, LDG, Ln-9 and MLC-A) were nebulized into the camera using the 6-jet Collison nebulizer, being assays performed for a total time of 100 min. Sampling by impact of air on a glass slide was carried out. Some conditions of equipment operation (phage suspension concentration, nebulization method, influence of relative humidity) using phage ATCC 8014-B1 were previously adjusted. Phages ALQ13.2, ATCC 15807-B1, BYM and CHD were not detected in the air because of loss of their infectivity after nebulization when assays in absence of catalyst and UV radiation were conducted. On the other hand, it was possible to achieve a complete inactivation (< 10 PFU mL−1) of phages ATCC 8014-B1, LDG and Ln-9 within 100 min of photocatalytic treatments. On the other, phage MLC-A was partially inactivated under the same conditions. These results are in agreement to those obtained when photonic and quantum inactivation efficiencies were calculated. In this sense, efficiencies varying between 1.27–2.64 × 10−17 PFU photon−1 and 4.42–9.18 × 10−17 PFU photon−1 were obtained, respectively, being the lowest efficiencies for phage MLC-A. This phage with the highest resistance could be studied in the future to evaluate diverse working conditions in order to optimize the operation and efficiency of the semi-pilot scale equipment.