Effectiveness of Low-Cost Bioreactors Integrated with a Gas Stripping System for Butanol Fermentation from Sugarcane Molasses by Clostridium beijerinckii

Abstract

The effectiveness of column bioreactors for butanol fermentation from sugarcane molasses by Clostridium beijerinckii TISTR 1461 was investigated. This fermentation was operated at an initial pH of 6.5 and temperature of 37 °C under anaerobic conditions. A 1-L bubble column bioreactor was used with various gas circulation rates ranging from 0.2 to 1.0 L/min. The highest butanol concentration (PB, 8.72 g/L), productivity (QB, 0.24 g/L∙h) and yield (YB/S, 0.21 g/g) were obtained with a gas circulation of 0.2 L/min. To improve butanol production efficiency, gas-lift column bioreactors with internal and external loops at 0.2 L/min of circulating gas were used. Higher PB (10.50–10.58 g/L), QB (0.29 g/L∙h) and YB/S (0.22–0.23 g/g) values were obtained in gas-lift column bioreactors. These values were similar to those using a more complex 2-L stirred-tank bioreactor (PB, 10.10 g/L; QB, 0.28 g/L h and YB/S, 0.22 g/g). Hence, gas-lift column bioreactors have potential for use as low-cost fermenters instead of stirred-tank bioreactors for butanol fermentation. When the gas-lift column bioreactor with an internal loop was coupled with a gas stripping system, it yielded an enhanced PB and sugar consumption of approximately 9% and 7%, respectively, compared to a system with no gas stripping.