Factors affecting the antifungal properties of Brevibacterium linens

Abstract

Abstract The antifungal properties of Brevibacterium linens against Aspergillus flavus were studied in relation to: incubation temperature and time, light, addition of proteolytic enzymes, heating, storage, pH value, and enrichment of the bacterial growth medium with l - or dl -methionine. The effect of adding different levels of B. linens culture and its cell-free supernatant to the fungal growth medium was also studied. The results indicated that B. linens produced antifungal compound(s) when grown in nutrient broth medium at 27°C with shaking at 110 rpm either in the presence or absence of light. The antifungal activity was maximal after 3–10 days. The antifungal compound seemed resistant to proteolytic enzymes, heat and storage and was most active at alkaline pH (optimum pH 11.0). The addition of l - or dl -methionine to the growth medium had no effect on the antifungal activity of B. linens. Growth, sporulation and production of aflatoxins of A. flavus were affected by the addition of B. linens culture and the effect was most pronounced when the B. linens culture was added at a level of 75%, v/v. Cell-free supernatants of 3- and 7-day-old B. linens culture had less antifungal activity than the parent cultures. The results give a basis to recommend B. linens for use as a biological control agent in the food industry.