Prevalence of Toxigenic Fungi in Egyptian Smoke-Dried Herring Fish: I- Antifungal Activity of Basil (Ocimum basilicum L.) Essential oil

A SURVEY was carried out on malt salt agar media to isolate and evaluate mycoflora occurring in samples of smoke-dried herring fish (Clupea harengus L.) that are ready for human consumption in Egypt. Aspergillus species were the most abundant fungi followed by Penicillium species then Fusarium species. Fungal genera of Cladosporium, Epicoccum, Mucor, and Rhizopus species were also isolated. A. flavus and A. fumigatus were the most frequently isolated aspergilli. P. griseofulvum was the most species common among penicillia, and F. solani was the predominant Fusarium species. C. cladosporioides was recovered in a high incidence. Findings of mycotoxins formation by the isolated mycoflora showed that some mycotoxins (aflatoxins, cyclopiazonic acid and kojic acid) were produced by some isolates of A. flavus. Some isolates of A. niger and A. fumigatus were able to produce kojic acid. A. ochraceus isolates produced penicillic acid but were not able to produce ochratoxin A. Two isolates of A. parasiticus were aflatoxin B1-producing and one isolate of A. versicolor produced sterigmatocystin. Concerning Fusarium species, some isolates of F. oxysporum and F. solani had the ability to produce cyclosporin A and zearalenone. The antibiotic, griseofulvin, citrinin and patulin were the characteristics metabolites produced by the toxigenic isolates of Penicillium species. This study was also extended to evaluate the efficacy of different concentrations of Ocimum basilicum L. essential oil on in vitro activity against the toxigenic isolated moulds. The recorded minimum inhibitory concentration (MIC) of the essential oil was 15% (v/v) with all the tested mould strains except A. niger, A. ochraceus (the MIC value was 10%, v/v) and Penicillium species (the MIC value was 20%, v/v). This oil was found to be fungicidal at all the tested concentrations. These findings indicate the possibility to use O. basilicum essential oil as a substitute for chemical additives to control fungal growth and toxins production