INHIBITION OF SURFACE GROWTH OF TOXIGENIC AND NONTOXIGENIC ASPERGILLI AND PENICILLIA BY EUGENOL, ISOEUGENOL AND MONOLAURIN

Abstract

Sabouraud dextrose agar, containing up to 300 ppm of eugenol, isoeugenol or monolaurin, was prepared. Eight strains of mycotoxin and non‐mycotoxin‐producing Aspergillus spp. and Penicillium spp. were tested. Spore suspensions were spotted in the center of agar plates and the linear (radial) growth rate was measured during incubation. All agents inhibited mold growth, but isoeugenol and eugenol were more effective than monolaurin. The average decreases in linear growth rate in the presence of eugenol, isoeugenol and monolaurin were 56, 43 and 11% at 100 ppm and 81, 85 and 15% at 200 ppm, respectively. At 300 ppm eugenol and isoeugenol, all fungi were inhibited completely; however, monolaurin (up to 2000 ppm) did not prevent mold growth. Except for P. viridicatum NRRL 6062, the molds tested did not vary significantly (at p=0.05) in degree of inhibition by any particular antifungal agent.A. parasiticus was grown in a yeast extract dextrose broth containing 100 ppm of the antifungal agents. Decreases in mycelial dry weight in the presence of eugenol, isoeugenol and monolaurin were 5.3, and 7.9, 10.5%, respectively. The corresponding reductions in aflatoxin B1 synthesized were 58, 57 and 25%. In conclusion, eugenol and isoeugenol have strong antifungal properties which are best manifested when the surface growth of molds on solid media is monitored.