Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2007
Publication Date: 12/8/2007
Citation: Pryor, S.W., Siebert, K., Gibson, D.M., Gossett, J.M., Walker, L.P. 2007. Modeling Production of Antifungal Compounds and their Role in Biocontrol Inhibitory Activity. Journal of Agricultural and Food Chemistry. 55:9530-9536. Interpretive Summary: The biological control agent, Bacillus subtilis, produces several families of antifungal compounds that are presumed to be important in the interactions with fungal pathogens for plant protection. The relationship of these compounds and other metabolites to antifungal activity, however, has not been well established. We took an empirical approach known as partial least squares regression modeling to identify the relative importance of individual metabolite concentrations to antifungal activity and under what conditions they are produced. This information should be useful in developing an optimal B. subtilis biological control product.
Technical Abstract: Partial Least Squares (PLS) regression modeling was used to relate the antifungal activity of B. subtilis solid-state fermentation extracts to the individual HPLC peaks from those extracts. A model was developed that predicted bioassay inhibition based on extract HPLC profile (R2 = 0.99). Concentrations of the members of the antifungal lipopeptide families iturin A and fengycin were found to correlate positively with extract inhibition, but a peak with unidentified chemical composition (designated as peak 48) showed the strongest correlation with extract inhibition. HPLC data were used to construct models for the production of iturin A, fengycin, and peak 48 as a function of substrate moisture content, incubator temperature, and aeration rate in the solid state bioreactors. Maximum production of all compounds occurred at the highest moisture content (1.7 g/g dry basis) and lowest incubator temperature (19ºC) tested. Optimal aeration rates for production of the two known lipopeptides and peak 48 were 0.1 L/min and 1.5 L/min, respectively.