Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/21/2006
Publication Date: 9/25/2006
Citation: Pryor, S.W., Gibson, D.M., Krasnoff, S.B., Walker, L.P. 2006. Identification of antifungal compounds in a biological control product using a microplate inhibition bioassay and ms analysis. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE). 49:1643-1649. Interpretive Summary: Biological control of plant pathogens through the use of microbial antagonists may be a more environmental friendly approach to controlling plant pathogens if they can be shown to be efficacious as well as cost effective relative to other treatments. Bacillus subtilis is a promising candidate for controlling pathogenic species of the fungal genera Fusarium as well as other plant pathogenic fungi. Although antimicrobial activity has been determined for some individual compounds produced by B. subtilis, there have been few studies that have combined component analysis of complex fermentation materials relative to biological activity. The purpose of this study was to demonstrate the use of the microplate bioassay as a method of evaluating relative activity of mixtures of bioactive compounds and to use the assay to partially characterize the spectrum of identified compounds produced by B. subtilis strain TrigoCor 1448 and their relative contribution to total activity of an extract against F. oxysporum f. sp. melonis. This information should be useful in the development and formulation of this organism as a fungal biological control agent.
Technical Abstract: An inhibition assay was developed to quantify the antifungal activity of a solid state fermentation of Bacillus subtilis. Methanol extracts were tested against a spore solution of the fungal pathogen Fusarium oxysporum f. sp. melonis using a 96-well microplate bioassay. HPLC analysis of extracts showed positive correlation between inhibition and levels of several active lipopeptides produced during fermentation. MS analysis confirmed the presence of the lipopeptides iturin A, fengycin, and surfactin. HPLC fractionation and subsequent bioassays established that the activity of the extracts was largely associated with the fraction containing fengycins. A smaller amount of activity was attributable to the fraction containing iturin A.