Inactivation of Aspergillus niger with photocatalytic paints

ZACARIAS, SILVIA MERCEDES; ROCÍO SCHUMACHER; FEDERICO SALVADORES; O. M. ALFANO; MARÍA DE LOS MILAGROS BALLARI

Buenos Aires

Congreso; 5th International Symposium on Environmental Biotechnology and Engineering 2016 (5ISEBE); 2016

Instituto de Investigación e Ingeniería Ambiental (3iA), UNSAM

Inactivation of Aspergillus niger with photocatalytic paintsS. M. Zacarías (1,2), R. Schumacher (2), F. Salvadores (1), O. M. Alfano (1), M. M. Ballari *(1,2) (1)INTEC (UNL-CONICET), Ruta Nacional Nº 168, Paraje "El Pozo", Santa Fe, Argentina(2)FBCB (UNL), Ruta Nacional Nº 168, Ciudad Universitaria UNL, Santa Fe, Argentina * ballari@santafeconicet.gov.ar (M. M. Ballari)Diverse microorganisms are transported as bioaerosols being a health risk for people living in indoor environments. A particular but very common problem is the fungus or mold growth in environments without ventilation and with high relative humidity (Sivasubramani et al. 2004). The heterogeneous photocatalysis is an efficient method for the chemical and biological purification of water and air. In this work the environmental fungi inactivation employing photocatalytic paint containing modified TiO2 was assessed for different illumination conditions (visible and UV light). Photocatalytic paint composed of water (30%), modified carbon doped TiO2 (active under visible radiation) Kronos vlp 7000 (18%), CaCO3 (18%), styrene-acrylic resin (33%) and dispersing agent (1%) was developed. Borosilicate glass plates of 2 cm × 2 cm were used as support to immobilize the paints. The ??dip-coating?? technique was employed to obtain the photocatalytic films (3 cm min-1, 25ºC). Aspergillus niger (ATCC 16404) conidia were used as model microorganism. 10 μL aliquots of the conidia suspension were spread over the coated plates. The dry plates were exposed to visible or UV radiation for different time periods. After the programmed irradiation time for each sample, the photocatalytic plates were removed and the remaining viable conidia were counted. Experimental results were fitted with the exponential equation N=N0 exp(-kt), where N (CFU mL-1) is the concentration of viable conidia, N0 (CFU mL-1) is the initial conidia concentration, k (day-1) is the apparent kinetic inactivation constant, and t (day) is the irradiation time.The inactivation of Aspergillus niger conidia was evaluated over diverse paints: the developed photocatalytic paint, a homemade non active paint, a commercial normal indoor paint, and a commercial ?antifungal? latex type paint. Significant conidia abatement was obtained for both radiation exposure, but principally applying UV light. The tested photocatalytic paint under visible light was even able to equal the fungus inactivation of a commercial antifungal paint with the disadvantage of employing sometimes harmful fungicides in its formulation. However, under conditions of visible radiation the photocatalytic effect of the modified carbon doped TiO2 in the paint was undistinguishable because similar inactivation levels of the Aspergillus niger were achieved when non-photoactive paints and surfaces were tested as the blanks. On the other hand, a greater environmental mold inactivation capacity by the photocatalytic paint was achieved when UV light was used as the photocatalyst activator. The photocatalytic oxidation power of the designed paint has been improved only when it was irradiated with UV light. Based on these results, a promising technology for microorganism control over photocatalytic coated surfaces can be expected for UV irradiated conditions, without the application of dangerous and toxic chemical fungicide in the paint. For forthcoming works new paint formulations using visible light photocatalysts and others indoor environmental conditions will be assessed to prove the fungicide effect of this photocatalytic building material under visible radiation.Keywords: PHOTOCATALYSIS; PAINT; FUNGI; INACTIVATION.