Effects of byproducts from acid hydrolysis of lignocellulose on butanol fermentation by clostridium acetobutylicum CICC8012

Abstract

Several byproducts of acid hydrolysis, including sodium acetate, formic acid, glucuronic acid, furfural, 5-hydroxymethylfurfural, sodium chloride, sodium sulfate, ferulic acid, coumaric acid, syringaldehyde and vanillin, were added into the medium at different concentrations to investigate their effects on butanol fermentation by Clostridium acetobutylicum CICC8012. The fermentation of butanol by the strain was strongly inhibited by formic acid and phenolic compounds. The butanol inhibition rate was 88.1%, 22.1% and 82.4% respectively when 0.5 g/L formic acid, ferulic acid or coumaric acid existed in the medium. Syringaldehyde (≥0.5 g/L) and vanillin (≥2 g/L) caused a much longer lag phase, but their negative effects on butanol fermentation were weaker than those of ferulic acid and coumaric acid. The butanol inhibition rate was 9.8%, 4.6% and 7.3% respectively when 1 g/L furfural, 5-hydroxiymethylfurfural or glucuronic acid existed in the medium. The butanol inhibition rate was 4.8% when 10 g/L sodium acetate existed in the medium. The inhibiting effects by furfural, 5-hydroxiymethylfurfural, glucuronic acid and sodium acetate were relatively weaker. It began to show inhibiting effects when the concentrations of sodium sulfate and sodium chloride exceeded 5 g/L. When their concentrations reached 20 g/L, the fermentation was almost inhibited. When the inhibitors were mixed together and their concentrations were above the critical point, the inhibiting effect was enhanced. The result of fermentation from wheat straw hydrolysate indicated that the composition of the hydrolysate was more complicated and the inhibiting effect was stronger. Fig 3, Tab 7, Ref 20.