Inhibitory effects of acids found in crude glycerol and lignocellulosic biomass on clostridium pasteurianum for butanol production
As fossil fuel resources decrease while pollution and greenhouse gas emissions from gasoline increase, the need for an alternative transportation fuel is pressing (Cassia et al. 2018). Current substitutes include ethanol-mixed gasolines, which have lower efficiency than gasoline and still rely on fossil fuels. Butanol, another possible gasoline substitution, is promising. It is a much more efficient fuel than ethanol and can be directly substituted for gasoline (Seggiani et al. 2012). Current techniques to mass-produce butanol depend on fermentation of sugars for butanol production. While sugar can be found in most natural matter, such as lumber or agriculture, it is an expensive material to process. In order to decrease the expense, agricultural waste, known as lignocellulosic biomass, is fermented instead (Baral et al. 2016). Another substrate that undergoes fermentation is crude glycerol, the waste product of producing biodiesel. Both crude glycerol and lignocellulosic biomass contain sugars that are fermentable. Certain strains of a bacterial genus Clostridium can ferment biomass and create acetone, butanol, and ethanol in a process known as ABE fermentation. A specific strain, Clostridium pasteurianum, is used in this study, as it has the ability to ferment sugars found in lignocellulosic biomass and crude glycerol (Venkataramanan et al. 2012). Unfortunately, both crude glycerol and lignocellulosic biomass also contain many toxic compounds, which kill or damage the bacteria and decrease butanol production. To ensure efficiency, it is important to determine which acids in these two substrates are causing inhibitory effects on Clostridium pasteurianum, specifically. This specific study investigates six different acids and their inhibitory effects on this strain of bacteria: D-glucuronic acid, furfural, hydroxymethylfurfural, levulinic acid, linoleic acid, and oleic acid. Based on these findings, furfural, linoleic, and oleic acid are the most toxic to Clostridium pasteurianum, and a tolerance to these specific acids should be engineered in order to create a more efficient butanol production system.