Bio-butanol fermentation using clostridium acetobutylicum and clostridium tetanomorphum in modified bioreactor flasks

Abstract

An alternative new generation biofuel to bio-ethanol has attracted researchers to investigate various approaches for optimization of traditional ABE fermentation to enable bio-butanol to be produced cheaper at an industrial scale. For instance, the use of different or modified Clostridium strains to enhance bio-butanol yields has been extensively studied. In this study, single-culture fermentation was investigated usingdifferentinoculum concentrations of Clostridium acetobutylicum andClostridiumtetanomorphum(3, 5, 10 % v/v) to ferment sweet sorghum juicewith a Brix index of 14°.Furthermore, co-culture fermentation were conducted using varying ratios of the two clostridium speciesin modified reactor flasks at pH 6-6.5, and incubated at 37oC while shaking (150rpm) for 96 hrs. Cell growth profileswere monitored using UV spectrophotometry at 600nm during both single and co-culture fermentation. Meanwhile, bio-butanol, residual sugars and by-products were analysed by high-performance liquid chromatography (HPLC).The results demonstrated that butanol and organic acids can be produced from sweet sorghum juice using a single culture, whereas co-culture only produced acids with no organic solvents. The highest butanol concentrationof6.49 g/L was obtained after96hrs using 10 % v/v C. acetobutylicumas a single culture. The highest organic acid concentration (Lactic acid) of 2.7 g/L was produced when an inoculum ratio of 6.5: 6.5 %v/v C. acetobutylicum to C. tetanomorphum were used and fermented for 96 hrs. Sweet sorghum juicehas potential as a cheaper substrate in producing high bio-butanol yield as a product in the presence of C.acetobutylicum. Co-culturescan also be used in fermentation of interest to produce high yields of organic acids