## 2 Materials and Methods
### Solid Residues Porosity  
The global porosity of the pretreated solid residues was estimated by the measurement of the water retention value (WRV) according to the ISO 23714:2014 standard procedure or calculated based on the mass removal, assuming a material density of 1.5 g/mL.  
To discriminate between the global porosity and the effective porosity for the enzymes to be applied later in the process, an attempt was done to determine the volumetric fraction of the solid residues' pores correspondent to a catalytic unit's hydrodynamic radius of a typical cellulase enzyme [18]. Dextrans and glucose were used as molecule probes: Dextran D11000 (Sigma-Aldrich, St. Louis, MO, USA) has a molecular weight of 9000-11,000 and a hydrodynamic radius of 2.65 nm, which is in the same order of magnitude of the catalytic unit of a typical cellulase enzyme [3]. Dextran D200000 (Sigma-Aldrich, St. Louis, MO, USA) has a molecular weight of 1,500,000-2,000,000 and a hydrodynamic radius of 35.06 nm. Glucose (Sigma-Aldrich, St. Louis, MO, USA) was also used as a probe molecule, to estimate the global porosity, assuming that its hydrodynamic radius (0.4 nm) is small enough to enter every pore.  
The probes hydrodynamic radii were calculated according to Equation (2) [25].  
\[\mathrm{r}=[0.53(\mathrm{M})^{0.5}]/2 \tag{2}\]  
where r is the hydrodynamic radius of the molecule (nm) and M is the molecular weight (g/mol).  
Solutions with a concentration of 4% (_in/v_) were prepared for each probe molecule. A given amount of solid residue, after centrifugation under the same conditions of the WRV procedure, was added to the probe solution to attain a solid content of 6% in the falcon tubes. The tubes were vigorously agitated to ensure a good dispersion of the solutions and the probes were left in contact with the biomasses for over 24 h. A blank was performed for each biomass, adding water to the tubes, instead of the probe solutions. All essays were performed in duplicate. Afterwards, the supernatant was recovered by centrifugation at 3000\(\times\)\(g\) for 15 min, covering the centrifuge tubes with parafilm to prevent water evaporation. The concentration of the probe in the supernatant was determined by measuring the rotation angle of polarized light in an ADP 220 Polarimeter (Bellingham & Stanley Ltd., Tunbridge Wells, UK), using water as baseline. The same procedure was followed for the blanks (to identify any carbohydrate possibly released from the pulp). The initial probe solutions were also tested. The decrease of the rotation angle in the samples, regarding the corresponding value for the initial probe solutions, which was attributed to the dilution water in the sample accessible to each probe, was calculated. It was assumed that the Dextran D2000000 does not penetrate the water inside the fiber wall and consequently the dilution effect observed corresponds to the free water. The added dilution observed for the Dextran D11000, regarding the D200000 was assumed as the water in the pores larger than 2.65 nm. The values are normalized by the precise number of solid residues, determined by drying at 105 \({}^{\circ}\)C.  
The external specific surface area (SSA) of the solid residues was determined using a LS Particle Analyzer (Beckman Coulter, LS 200, CA, USA).