Fed-batch fermentation for n-butanol production from cassava bagasse hydrolysate in a fibrous bed bioreactor with continuous gas stripping

Concentrated cassava bagasse hydrolysate (CBH) containing 584.4 g/L glucose was studied for acetone–butanol–ethanol (ABE) fermentation with a hyper-butanol-producing Clostridium acetobutylicum strain in a fibrous bed bioreactor with gas stripping for continuous butanol recovery. With periodical nutrient supplementation, stable production of n-butanol from glucose in the CBH was maintained in the fed-batch fermentation over 263 h with an average sugar consumption rate of 1.28 g/L h and butanol productivity of 0.32 ± 0.03 g/L h. A total of 108.5 g/L ABE (butanol: 76.4 g/L, acetone: 27.0 g/L, ethanol: 5.1 g/L) was produced, with an overall yield of 0.32 ± 0.03 g/g glucose for ABE and 0.23 ± 0.01 g/g glucose for butanol. The gas stripping process generated a product containing 10–16% (w/v) of butanol, ∼4% (w/v) of acetone, a small amount of ethanol (<0.8%) and almost no acids, resulting in a highly concentrated butanol solution of ∼64% (w/v) after phase separation.