Switchgrass Extractives Have Potential as a Value-added Antimicrobial Against Plant Pathogens and Foodborne Pathogens

Panicum virgatum (switchgrass), a perennial grass native to North America, is a leading biomass feedstock candidate for the manufacture of cellulosic ethanol. Switchgrass is considered a viable option for biofuel production due to its cheap production cost and ability to grow on marginal land. Biofuel derived from switchgrass has been shown to be very energy efficient, producing 540% more renewable energy versus nonrenewable energy expended. Switchgrass-derived biofuel is also estimated to have greenhouse gas emissions that are 94% lower than emissions from gasoline (Schmer et al 2008). Biofuels are created through biochemical processes that utilize various enzymes and microorganisms for conversion of cellulose to ethanol. During this process, switchgrass extractives can be eliminated to allow for optimum enzyme activity, and improved efficiency of the conversion process (Thammasouk et al. 1997). Switchgrass extractives removed during this process are rich in phenolic compounds that are known to have antibacterial and antifungal properties. These compounds are concomitant with the induction of the systemic resistance response exhibited by stressed or diseased plants (Chen et al. 2010). If the extractives are not removed during the biofuel production process, the phenolic compounds will inhibit microbial and enzymatic function and decrease ethanol yield. The goal of this research was to assess the efficacy of switchgrass extractives as an antimicrobial for use as a commercial value-added product to switchgrass-derived biofuels. Specifically, the objectives of this research were to test for antimicrobial activity of concentrated switchgrass extractives against bacterial plant pathogens, fungal plant pathogens, and bacterial foodborne pathogens.