Purpose: The aim of this investigation was to evaluate the effect of UVC light on Aspergillus and Penicillium species on moist and dry surfaces.
Methods: Ten Aspergillus and ten Penicillium species were used in this study. For the moist surface method, 0.1 ml of mold spore suspensions (~ 102 to 103 spores/plate) were spread on MEA plates and exposed to UVC treatment (254 nm) for 0, 5, 10, 15, 30, 60, 120, and 150 seconds. For the dry surface method, mold spores (~ 105 spores) were dried onto a membrane filter, and then treated with UVC (254 nm) for 0, 30, 60, 120, 180, and 300 seconds. The membranes were placed in 0.1% sterile peptone water, mixed in a stomacher, diluted, and plated onto MEA plates. All plates were incubated at 25°C for three days. Colonies were counted. All the experiments were done in triplicate.
Results: On moist surfaces, after 30 seconds exposure, 70 to 99% reductions were observed for most of the species tested. On the dried filter membranes, a reduction of viable spores of up to 3.6 log was observed after 180 s exposure. Mold species with dark pigmented spores, such as Aspergillus carbonarius, were more resistant to UVC. Penicillium species were significantly (P<0.001) more sensitive to UVC, with approximately three-log reduction in comparison with one to two-log reduction for the Aspergillus species.
Significance: UVC light treatment is an effective process for inactivating mold spores on moist and dry surfaces. Longer exposure periods should be used for dry surfaces.