Photodynamic inactivation of Aspergillus flavus mediated by Bidens pilosa extract

Abstract

Occurrence of mycotoxins in food and animal feeds poses major health risks to human  and animals, and effective control requires integration of crop management strategies  both in the field and during post-harvest storage and processing. Photodynamic  inactivation is a novel light-based approach which offers a promising alternative to  conventional methods for the control of mycotoxigenic fungi. An experimental study was conducted to assess the effectiveness of photoinactivation of Aspergillus flavus, a major aflatoxin-producing fungal species, by photosensitization mediated by an extract of the tropical plant Bidens pilosa. Photosensitization was conducted on fungal spores and hyphae in solution using of 420 nm wavelength light at a dose of 60 J cm^-2 combined with 0.25 and 0.5 mg ml^-1 of the plant water extract. The numbers of viable spores and hyphae were reduced by 4 log colony forming units (CFU ml^-1) and this was affected by changing temperature but not pH. The findings of this study indicate the potential of using photosensitization technique utilizing natural photosensitizers derived from locally available herbs to effectively control mycotoxins in feeds for improved livestock production.

Keywords: Aspergillus flavus, Bidens pilosa, light, mycotoxins, photosensitization