Cellulosic Bioethanol from Industrial Eucalyptus globulus Bark Residues Using Kraft Pulping as a Pretreatment

The pulp and paper industry faces an emerging challenge for valorising wastes and side-streams generated according to the biorefinery concept. Eucalyptus globulus bark, an abundant industrial residue in the Portuguese pulp and paper sector, has a high potential to be converted into biobased products instead of being burned. This work aimed to evaluate the ethanol production from E. globulus bark previously submitted to kraft pulping through separate hydrolysis and fermentation (SHF) configuration. Fed-batch enzymatic hydrolysis provided a concentrated hydrolysate with 161.6 g center dot L-1 of cellulosic sugars. S. cerevisiae and Ethanol Red(R) strains demonstrated a very good fermentation performance, despite a negligible xylose consumption. S. passalidarum, a yeast known for its capability to consume pentoses, was studied in a simultaneous co-culture with Ethanol Red(R). However, bioethanol production was not improved. The best fermentation performance was achieved by Ethanol Red(R), which provided a maximum ethanol concentration near 50 g center dot L-1 and fermentation efficiency of 80%. Concluding, kraft pulp from E. globulus bark showed a high potential to be converted into cellulosic bioethanol, being susceptible to implementing an integrated biorefinery on the pulp and paper industrial plants.

Automated summary

The study demonstrated that Eucalyptus globulus bark has the potential to be converted into biobased products, particularly bioethanol, with high efficiency, especially when subjected to kraft pulping. Yeasts such as S. cerevisiae and Ethanol Red(R) showed good fermentation performance, making them ideal for ethanol production.