2026-04-20T11:30:56Zhttps://riubu.ubu.es/oai/request

oai:riubu.ubu.es:10259/66582022-05-20T13:21:59Zcom_10259_4244com_10259_5086com_10259_2604col_10259_4569

00925njm 22002777a 4500 dc Alonso Riaño, Patricia author Melgosa Gómez, Rodrigo author Trigueros Andrés, Ester author Beltrán Calvo, Sagrario author Sanz Díez, Mª Teresa author 2022 Brewer ́s spent grain (BSG) is the solid by-product generated in breweries after the mashing and wort filtration process. It comprises about 85 % of the total by-products, generating approximately 20 kg per 100 L [1]. BSG presents a valuable chemical composition with a high content of protein and carbohydrates, 5 % of lipids and an important source of phenolic compounds. Among the different techniques proposed to valorize BSG, supercritical CO2 (sc-CO2) has become a promising technology to process biomass. The main aim of this work was to assess the effect of sc-CO2, after BSG oil extraction, on the subsequent enzymatic hydrolysis to hydrolyze the polysaccharide fraction into monomeric sugars by comparing the sugar yields of sc-CO2 and non-scCO2 treated BSG. After sc-CO2 treatment at 40 MPa and 80 oC, the raffinate obtained was subjected to enzymatic hydrolysis by cellulase at different enzyme dose. At the sc-CO2 extraction the carbohydrate fraction remained in the raffinate phase after extraction. Glucose yield increased with enzyme concentration for non-treated and sc-CO2 treated BSG. Higher yields of glucose were obtained for sc-CO2 treated compared to non-treated sc-CO2 for all the enzymes concentrations. The percentage increase in glucose yield for sc-CO2 treated and non-treated BSG was 8, 14 and 18 % for the three cellulase concentrations essayed in this work, 0.25, 0.5 and 1 %, respectively. The hydrolysis kinetics for xylose and arabinose have been also determined for non-treated and sc-CO2 treated BSG at 1 % of cellulase dose. Although not big differences were observed in the final sugar yield in the hydrolysates, the initial hydrolysis rate were significant higher for the sc-CO2 treated BSG than for the untreated samples. The higher enzymatic hydrolysis rate and yield obtained in the raffinate-BSG after sc- CO2 treatment compared with non-treated BSG could be attributed partially to the removal of the lipid fraction. As it has been described in literature [2], fats and oils could influence the susceptibility of carbohydrates to enzymes. This improvement was also due to surface morphology modification. The structural and chemical changes of untreated and sc-CO2 treated BSG was assessed by scanning electron microscopy and X-ray powder diffraction (XRD). Although the XRD pattern after sc-CO2 treatment indicated that the pre-treatment was not strong enough to modify the BSG crystallinity, the raffinate exhibited an irregular porosity and lamellar structure. sc-CO2 broke partially some structural barriers allowing a better enzyme access. Furthermore, some phenolic compounds were determined in the enzymatic hydrolysates at the end of the hydrolysis by using 1 % of cellulase (Table 1). It was observed that for p-coumaric acid and ferulic acid, a concentration 31 and 24 % higher, respectively, was obtained in the BSG hydrolysates after sc-CO2 treatment, while for vanillin similar concentration was obtained in both hydrolysates. The concentration of p-coumaric acid and vanillin after cellulase hydrolysis was lower than the values previously reported for the same BSG by alkaline, xylanase (1%) and subcritical water hydrolysis [3], [4]. Nevertheless, for ferulic acid, only a higher value was reached for alkaline hydrolysis. http://hdl.handle.net/10259/6658 Modification of brewer’s spent grain after sc-CO2 extraction: improvement of sugar and phenolic compounds release