Acetone, butanol, and ethanol production from the green seaweed Enteromorpha intestinalis via the separate hydrolysis and fermentation

Acetone, butanol, and ethanol (ABE) were produced following the separate hydrolysis and fermentation (SHF) method using polysaccharides from the green macroalgae Enteromorpha intestinalis as biomass. We focused on the optimization of enzymatic saccharification as pretreatments for the fermentation of E. intestinalis. Pretreatment was carried out with 10% (w/v) seaweed slurry and 270-mM H2SO4 at 121 °C for 60 min. Monosaccharides (mainly glucose) were obtained from enzymatic hydrolysis with a 16-U/mL mixture of Celluclast 1.5 L and Viscozyme L at 45 °C for 36 h. ABE fermentation with 10% (w/v) E. intestinalis hydrolysate was performed using the anaerobic bacteria Clostridium acetobutylicum with either uncontrolled pH, pH controlled at 6.0, or pH controlled initially at 6.0 and then 4.5 after 4 days, which produced ABE contents of 5.6 g/L with an ABE yield (YABE) of 0.24 g/g, 4.8 g/L with an YABE of 0.2 g/g, and 8.5 g/L with an YABE of 0.36 g/g, respectively.