The Effect of Initial Butyric Acid Addition on ABE Fermentation by C.acetobutylicum NCIMB 619 Siti Jamilah Hanim Mohd Yusof 1 , Mohd Sobri Takriff 2 , Abdul Amir Hassan Kadhum 2 , Abdul Wahab Mohammad 2 and Jamaliah Jahim 2 1 School of Bioprocess Engineering, Universiti Malaysia Perlis, Kompleks Pusat Pengajian Jejawi 3, 02600 Arau, Perlis 2 Chemical and Process Engineering Department, Faculty of Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Abstract. The addition of organic acids to the growth medium has been shown to stimulate solvent production and protect against the degeneration of ABE-producing clostridia. The objective of this study is to demonstrate the effect of introduction of butyric acid in the fermentation media on the solvent production by C. acetobutylicum NCIMB 619. In this study, batch cultures were carried out in Reinforced Clostridial Media (RCM) containing 0.0015, 2.0 and 5.0 g/l of butyric acid, simultaneously with a control media (without addition of butyric acid) at 37°C for 72 hours. Samples were periodically withdrawn for analysis purposes. It was found that the presence of butyric acid during the early stage of the fermentation process favor the solvent yield to glucose utilization and productivity up to 139%. By adding butyric acid, the concentration of acetone, butanol and ethanol generated was improved significantly. In the case of 5.0 g/l butyric acid addition, acetone, butanol and ethanol production was increased approximately 92, 8 and 2 folds, respectively compared to control culture. The result obtained in this study showed that the addition of butyric acid has successfully enhanced the cell growth and subsequently promoted solvent production by C. acetobutylicum NCIMB 619. Keywords: Acetone-butanol-ethanol, organic acid, clostridia. 1. Introduction The production of butanol by acetone-butanol-ethanol (ABE) fermentation used to be one of the largest bioprocesses until the 1950s, but later it was replaced by the less expensive petroleum-based chemical synthesis. In recent years, interest in bio-based butanol has been revived primarily due to concerns with fossil fuel depletion, and microbial production of butanol is considered to be a potential source of liquid fuels. The metabolic pathway of solvent-producing Clostridium consists of two distinct phases, acidogenesis and solventogenesis [1]. In general, during acidogenesis, cell growth is exponential and organic acids are produced together with hydrogen gas, which results in pH reduction. Solventogenesis followed subsequently where cell growth enters the stationary phase and the organic acids are reutilized to produce acetone, butanol and ethanol. This reutilization of organic acids increases the pH value of the broth. It was reported that the addition of organic acids in the broth triggered the metabolic transition from the acidogenic phase to solventogenic phase [1-4]. Therefore in the present study, butyric acid was introduced early in the fermentation media to demonstrate its contribution in solvent production. 2. Approach and Methods + Corresponding author. Tel.: +6049766340; fax: +6049798755. E-mail address: jamilahhanim@unimap.edu.my 2012 2nd International Conference on Environment Science and Biotechnology IPCBEE vol.48 (2012) © (2012) IACSIT Press, Singapore DOI: 10.7763/IPCBEE. 2012. V48. 19 100