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Comprehensive study on the effects of process parameters of alkaline thermal pretreatment followed by thermomechanical extrusion in sugar liberation from Eucalyptus grandis wood

Pablo Doménech ORCID logo, Paloma Manzanares, Cristina Álvarez, Mercedes Ballesteros and Aleta Duque
From the journal Holzforschung


A combination of alkaline thermal pretreatment followed by thermomechanical extrusion was studied as a novel sequential pretreatment process for an effective breakdown of the lignocellulosic structure of Eucalyptus grandis wood (EW). The first step was studied by analysing the influence of two factors: the NaOH-to-dry biomass ratio or NaOH loading (NaOH/DM) and the liquid-to-solid ratio (L/S). Optimization of these two parameters provided good results in terms of enzymatic hydrolysis at 5% (w w−1) solids loading, obtaining a total sugar concentration of 24.9 g L−1 and a total sugar production of 36.9 g 100 g−1 raw EW after pretreating the biomass at 20% NaOH/DM and L/S = 1/1. The second step of extrusion, when followed by a final washing step, provided a significant increase in glucose and xylose production when working at 10% NaOH/DM. For a soda loading of 20%, there was a clear improvement in sugars conversion yield after extrusion and washing: 71% for glucan conversion and 89% for xylan.

Corresponding author: Pablo Doménech, Biofuels Unit, Energy Department – CIEMAT, Avda. Complutense 40, 28040, Madrid, Spain, E-mail:

Funding source: European Commission

Award Identifier / Grant number: 654365


The authors would like to thank the INIA (Uruguay) for kindly providing the eucalyptus biomass used for all experiments and Novozymes A/S (Denmark) for kindly providing the enzymatic cocktail used for saccharification.

  1. Author contribution: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: This work was carried out in the frame of the BABET-REAL5 Project. The project is co-funded by the European Union within the Horizon 2020 programme Grant Agreement No. 654365.

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.


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Received: 2020-03-11
Accepted: 2020-07-01
Published Online: 2020-08-19
Published in Print: 2021-03-26

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