CONICET | Buscador de Institutos y Recursos Humanos

IntroductionPhages infections constitute the main cause of failure of starter cultures during fermented dairy products manufacturing, and can lead to significant technological difficulties and economic losses. Bioaerosols constitute the main dissemination via of phages in industrial environments [1]. The aim of this work was to study diverse oxidation advanced processes as an alternative to reduce the phage concentration in the surface/air. Materials and MethodsThe following assays were performed in a laboratory scale reactor constituted by two separate compartments, an emission source constituted by seven lamps and an irradiation chamber where phage suspensions were placed for irradiation:Photocatalytic paints: phage suspensions were deposited and dried on the coated plates with photocatalytic paints (0.71 mg modified carbon doped TiO2 anatase/cm2). Inactivation assays were performed for sixteen phages, with a total time of 20 h at 30°C and 80% RH under radiation typically used for indoor illumination (λ = 360 - 720 nm) [2]. Photocatalysis (TiO2, UV-A): drops of phage particles were deposited on plates coated with TiO2 (0.02 mg/cm2). Inactivation assays were performed for seventeen phages under UV-A radiation (λ = 200 - 400 nm), for a period of 3 h at 40°C and 89.5% RH [3]. Afterwards, assays were performed in a semi-pilot reactor in order to analyze the inactivation efficiencies in air. The reactor is a close system with recirculation constituted by a chamber where phage particles were nebulized for a total time of 30 min using the 6-jet Collison nebulizer and a photocatalytic reactor with the UV emission system (20 lamps). An axial fan provided a forced air circulation coming from the chamber and a polypropylene tube connected the exit of the photocatalytic reactor with the chamber, allowing phage recirculation. Assays were performed for four phages under UV-A radiation (λ = 200 - 400 nm) and presence of photocatalyst (1.77 mgTiO2/cm2) for a total time of 100 min [1]. For all assays, borosilicate glass plates were used to deposit the catalyst. Phage inactivation as function of time (Log PFU/mL vs time) was evaluated and photonic and quantum inactivation efficiencies were calculated, that is the relations of the inactivation rate per the incident radiation flux and per the rate of absorbed radiation, respectively.Results and DiscussionPhotocatalytic paints: eight phages were completely inactivated within 1.5 and 5 h of treatment, reaching reductions higher than 2.79 log orders, whereas other eight phages reduced their infectivity between 2.33 and 5.88 log orders, within 4 and 20 h. Photonic efficiencies ranged from 2.84×109 to 4.06×1012 PFU/Einstein and quantum efficiencies ranged from 6.40×109 to 9.17×1012 PFU/Einstein.Photocatalysis (TiO2, UV-A): some phages were completely inactivated after 60 - 120 min of treatment, while others maintained their infectivity even after 180 min. Photonic efficiencies ranged from 3.63×109 to 4.82×1010 PFU/Einstein and quantum efficiencies ranged from 1.03×1011 to 1.37×1012 PFU/Einstein.Photocatalytic treatments to airborne phages: three phages were completely inactivated within 100 min of treatment whereas one was partially inactivated under the same condition. Photonic efficiencies ranged from 7.65×106 to 1.59×107 PFU/Einstein and quantum efficiencies ranged from 2.66×107 to 5.53×107 PFU/Einstein.Significance or Main ConclusionsThe results obtained demonstrated a phage dependent behavior and the feasibility of oxidation advanced processes (photocatalysis and photocatalytic paints) as simple methodologies that could complement those habitually applied in laboratories and industrial plants handling lactic acid bacteria, in order to reduce the frequency of phage attacks. References [1] M. Briggiler Marcó et al.; J. Photochem. Photobiol. A Chem. 409 (2021) 987-993.[2] S. Zacarías et al.; J. Photochem. Photobiol. A Chem. 364 (2018) 76-87. [3] M. Briggiler Marcó et al.; Chem. Eng. J. 172 (2011) 987-993.

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