The feasibility of an industrial-scale subcritical water (SW) system by scaling up from laboratory to pilot scale in
a discontinuous operation mode has been investigated regarding the valorization of brewer´s spent grain (BSG).
The subcritical water treatment (SWT) of BSG at the pilot scale in a discontinuous mode at 170 ◦C and 22 min,
resulted in the release of 56% of the total carbohydrates present in the BSG. A total pentose yield of 78% was
achieved (18% as monomer and 82% as oligomer). The concentration of inhibitors in the hydrolysate was
relatively low, 0.22 g/L, 0.31 g/L, and 0.13 g/L of furfural and acetic and formic acids respectively. Other highvalue compounds were obtained, such as 6.5 g peptides/L (64% protein yield), 21 mg free amino acids/g protein
(2.17% aa yield), and a total phenolic content (TPC) of 17.84 mg GAE/g dry BSG. In general, the results showed
good reproducibility when scaling up from laboratory to pilot SW process. Good reproducibility of the scale-up
was found for the release yield of arabinoxylo-oligomers, and gluco-oligomers from BSG, also for the protein
yield and the release of free amino acids. However, the xylo-oligomers yield was 13% higher at the lab scale than
at the pilot scale and higher concentrations of monomers and phenolic compounds were found in the SW hydrolysates obtained at the lab scale. Differences in the preheating time in both systems seem to have an effect on
the hydrolysis yield of some the biopolymers. SWT modified the composition of the residual solid, as a decrease
in the concentration of hemicellulose and an increase in the glucan content was observed, which may enhance
the digestibility of the solid improving a further enzymatic release of glucose from the remaining solid.
