High yield bio-butanol production by solvent-producing bacterial microflora

Highly efficient butanol-producing bacterial microflora were isolated from hydrogen-producing sludge of a sewage treatment plant. Based on denaturing gradient gel electrophoresis (DGGE) analysis and 16s rDNA comparison, four strains from the butanol-producing microflora were identified as Clostridium saccharoperbutylacetonicum, Clostridium butylicum, Clostridium beijernckii, and Clostridium acetobutylicum. The effects of glucose, FeSO4·7H2O and yeast extract concentrations on the butanol production by the mixture culture were investigated on batch mode. The medium composition for bio-butanol production was optimized using the Box–Behnken design and response surface methodology (RSM). The maximum butanol production rate (0.25 ± 0.02 g/L-h) and concentration (12.4 g/L) were obtained under the condition of glucose concentration, 60 g/L; FeSO4·7H2O, 0.516 g/L; yeast extract concentration, 5.13 g/L. Addition of 6.0 g/L butyric acid significantly increased the butanol titer to 17.51 ± 0.49 g/L. Pressurized fermentation strategy (employed with a 5 L fermentor) further enhanced the butanol concentration to 21.35 g/L, along with a maximum butanol rate of 1.25 g/L-h.

► Efficient butanol-producing bacterial microflora were isolated from sewage sludge.
► Medium optimization by RSM marked enhance bio-butanol production.
► Butyric acid addition and pressurized fermentation led to the highest performance.
► The obtained butanol titer and production rate are among the world’s top performance.