Lignocellulosic degradation compounds, especially phenolic compounds, inhibit the fermentation of Clostridium strains. In this study, a simple in situ detoxification method using a surfactant was developed for butyric acid production by Clostridium tyrobutyricum ATCC25755. Tween 80, a non-ionic surfactant, was chosen to sequester inhibitors by forming micelles, consequently preventing direct contact of inhibitors with cell membranes. When Tween 80 was added during fermentation, butyric acid production was significantly enhanced in the presence of hydrophobic phenolics such as p-coumaric acid (0 vs. 3.1 g/L butyric acid) and ferulic acid (2.2 vs. 4.6 g/L butyric acid) even at 0.016 g/L of Tween 80 (corresponding to the critical micelle concentration). Lignin, a polyphenol compound in lignocellulose, was also detoxified by Tween 80. When Tween 80 was added to acid-pretreated rice straw hydrolysate, butyric acid production significantly increased (0.1 vs. 8.7 g/L butyric acid), thus verifying detoxification effect of Tween 80 on lignocellulosic hydrolysate. (C) 2015 Elsevier Ltd. All rights reserved.