Direct and rapid discrimination of aflatoxigenic strains based on fibre-optic room temperature phosphorescence detection

Abstract

An innovative analytical methodology for the rapid identification of aflatoxin-producing moulds belonging to Aspergillus genus is presented here. The procedure is based on the measurement, using a fibre-optic luminometer, of the room temperature phosphorescence (RTP) emitted by aflatoxins produced by isolated aflatoxigenic strains, cultured in a special culture medium consisting of malt extract agar modified with β-cyclodextrin and sodium deoxycholate for RTP induction. Unequivocal detection of the presence of aflatoxins in the culture medium is achieved within the first 36 h of incubation at 32 °C, owing to the selectivity and sensitivity of the RTP emission, as compared with the minimum of 72 h needed using a conventional microbiological method. In a first step, the capability of aflatoxin standard solutions to emit analytically useful RTP was evaluated. In this line all experimental conditions were optimised for in vitro induction of RTP from aflatoxins. In a second step, a simple analytical test was developed and it has been evaluated for the rapid identification of aflatoxigenic strains, as a discriminating assay from non-aflatoxigenic strains based on the measurement of experimental RTP emission observed. Confirmation of aflatoxin production on the studied culture plates was accomplished by means of an HPLC/fluorescence reference method.