Improvement of butanol production from sweet sorghum juice by Clostridium beijerinckii using an orthogonal array design

• Sweet sorghum juice was used as butanol production medium by Clostridium beijerinckii.
• Three main factors were optimized using orthogonal array design.
• Optimum CaCO3, (NH4)2SO4 and butyric acid were 7, 1.25 and 6 g/L, respectively.
• Butanol concentration and productivity were 15.46 g/L and 0.43 g/L h, respectively.

Optimization of three chemical supplements: CaCO3 (4–10 g/L), (NH4)2SO4 (0.50–2.00 g/L) and butyric acid (3–9 g/L) for high levels butanol production by Clostridium beijerinckii TISTR 1461 from sweet sorghum juice was attempted using an L9 (34) orthogonal array design (OAD). The fermentation was carried out at 37 °C in 1-L screw-capped bottles under strictly anaerobic conditions. The OAD results showed that the optimum concentrations of CaCO3, (NH4)2SO4 and butyric acid for butanol fermentation were 7, 1.25 and 6 g/L, respectively. The butanol concentration (Pb) and productivity (Qb) values of the verification experiment under the optimum conditions in a 5-L fermenter were 15.46 g/L and 0.43 g/L.h, respectively at 36 h. The chemicals influencing the Pb and Qb values in descending order were butyric acid > CaCO3 > (NH4)2SO4. In the control treatment (sweet sorghum juice without chemical supplementation), the Pb and Qb values were only 0.64 g/L and 0.02 g/L.h, respectively.