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

Abstract

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 L−1 of cellulosic sugars. S. cerevisiae and Ethanol Red® 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®. However, bioethanol production was not improved. The best fermentation performance was achieved by Ethanol Red®, which provided a maximum ethanol concentration near 50 g 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.

Subcritical Water as Pretreatment Technique for Bioethanol Production from Brewer’s Spent Grain within a Biorefinery Concept

“…As expectable, xylose contribution to ethanol production was not remarkable since pentose sugars are not easily metabolized. Amândio et al [ 35 ] also reported slight xylose consumption by Ethanol Red ® . In the present work, the maximum concentration of glycerol, 0.677 ± 0.005 g/L, was achieved at 13 h, showing a minor decrease after that.…”

Valorization of Brewer's Spent Grain by Furfural Recovery/Removal from Subcritical Water Hydrolysates by Pervaporation

“…This phenomenon is known as diauxic effect, consisting in glucose preference when the fermentation broth contains both glucose and xylose. Higher rate of xylose consumption was observed only after full consumption of glucose [30]. Arabinose and xylose exhaustion were detected only after 24 h, but certainly it might be occurred significantly earlier given its consumption profile.…”

Getting Value from Pulp and Paper Industry Wastes: On the Way to Sustainability and Circular Economy

“…Regarding bark, the use of a pretreatment step has been extensively studied [18]. The main pretreatments employed were kraft pulping and hot water extraction (HWE) [26,40,41,131,132]. Besides these two processes, steam explosion (SE) was also extensively applied to sawdust [48,50,59,[133][134][135].…”

“…Regarding the conversion of E. globulus bark into bioethanol, studies are scarce (Table 1). Recently, Amândio et al [132] assessed the bioethanol production from E. globulus bark previously submitted to kraft pulping through SHF configuration. The maximum ethanol concentration of 50.8 ± 0.5 g L −1 was achieved using Ethanol Red ® (Saccharomyces cerevisiae yeast) after 20.5 h, corresponding to the productivity of 2.48 ± 0.02 g L −1 h −1 and 81.0 ± 0.6% of the theoretical yield (0.511 g ethanol g sugars −1 ) [132].…”