Cellulose hydrolysis and IBE fermentation of eucalyptus sawdust for enhanced biobutanol production by Clostridium beijerinckii DSM 6423

Abstract

Butanol has shown to have superior fuel properties when compared to ethanol and has many applications in chemicals industries. It can be produced by isopropanol-butanol-ethanol (IBE) fermentation by some natural Clostridium beijerinckii strains that can produce isopropanol instead of acetone, along with butanol and ethanol, producing an alcohol biofuel mixture. In this work, biobutanol production from eucalyptus sawdust by cellulose hydrolysis and fermentation was evaluated. Eucalyptus sawdust was first subjected to autohydrolysis pretreatment at mild severe conditions (180 °C, 45 min) to enhance the hemicellulose recovery and preserve the xylan fractions (xylose and xylo-oligomers) for further processing. The pretreated solids obtained were subjected to enzymatic hydrolysis and fermentation under different process configurations: separate hydrolysis and fermentation (SHF), simultaneous hydrolysis and fermentation (SSF), and pre-saccharification and simultaneous saccharification and fermentation (PSSF). Butanol and IBE concentrations of 4.2 g/L and 8.7 g/L were achieved in SHF at 48 h, which resulted 35% and 45% higher than in SSF, respectively. Under this condition, the butanol yield reached 0.15 gbutanol/gsugars, which allowed to achieve a process efficiency of butanol production from eucalyptus sawdust of 12%.