Efficient acetone-butanol-ethanol production by Clostridium beijerinckii from sugar beet pulp

Sugar beet pulp (SBP) has been investigated as a promising feedstock for ABE fermentation by Clostridium beijerinckii. Although lignin content in SBP is low, a pretreatment is needed to enhance enzymatic hydrolysis and fermentation yields. Autohydrolysis at pH 4 has been selected as the best pretreatment for SBP in terms of sugars release and acetone and butanol production. The best overall sugars release yields from raw SBP ranged from 66.2% to 70.6% for this pretreatment. The highest ABE yield achieved was 0.4 g/g (5.1 g/L of acetone and 6.6 g/L butanol) and 143.2 g ABE/kg SBP (62.3 g acetone and 80.9 g butanol) were obtained when pretreated SBP was enzymatically hydrolyzed at 7.5% (w/w) solid loading. Higher solid loadings (10%) offered higher acetone and butanol titers (5.8 g/L of acetone and 7.8 g/L butanol). All the experiments were carried out under not-controlling pH conditions reaching about 5.3 in the final samples.