LAUSR

Abstract. Weak acids released during hydrolysis of lignocellulosic biomass are potential inhibitors of microorganism fermentation. In this study, the effects of formic and levulinic acids on butyric acid synthesis by were investigated. With the addition of 1.2 to 4.8 g L-1 of formic acid, increased lag time, decreased cell density, and lower butyric acid productivity were observed. Up to 15% and 56% reduction in peak cell density and butyric acid productivity, respectively, were caused by formic acid addition, whereas there was no significant difference in butyric acid yield between the control and formic acid treated groups (except for the 2.4 g formic acid L-1 treatment). Levulinic acid did not show any notable effects on within the investigated concentration range (0 to 4.8 g L-1). Overall, showed strong tolerance of both formic and levulinic acids, but neither of these acids could be metabolized by the microbe.HighlightsFormic acid had dosage-dependent inhibitory effects on C. tyrobutyricum.Levulinic acid had no effects on cell growth or butyrate synthesis.Neither formic acid nor levulinic acid was metabolized by C. tyrobutyricum.C. tyrobutyricum showed strong tolerance to formic acid and levulinic acid. Keywords: Butyric acid, Clostridium tyrobutyricum, Formic acid, Levulinic acid, Lignocellulosic hydrolysate, Xylose.