The application of supercritical fluids technology to recover healthy valuable compounds from marine and agricultural food processing by-products: a review

Food by-products contain a remarkable source of bioactive molecules with many benefits for humans; therefore, their exploitation can be an excellent opportunity for the food sector. Moreover, the revalorization of these by-products to produce value-added compounds is considered pivotal for sustainable growth based on a circular economy. Traditional extraction technologies have several drawbacks mainly related to the consumption of hazardous organic solvents, and the high temperatures maintained for long extraction periods which cause the degradation of thermolabile compounds as well as a low extraction efficiency of desired compounds. In this context, supercritical fluid extraction (SFE) has been explored as a suitable green technology for the recovery of a broad range of bioactive compounds from different types of agri-food wastes. This review describes the working principle and development of SFE technology to valorize by-products from different origin (marine, fruit, vegetable, nuts, and other plants). In addition, the potential effects of the extracted active substances on human health were also approached.Axencia Galega de Innovación | Ref. IN607A2019 / 01European Commission | Ref. H2020, AQUABIOPRO-FIT, n. 790956CYTED | Ref. 119RT0568Ministerio de Economía y Competitividad | Ref. RYC2018-026177-IChina Scholarship Council (CSC) | Ref. 201908420246China Scholarship Council (CSC) | Ref. 201908420245Generalitat Valenciana | Ref. IDIFEDER / 2018 / 04

A Comparative Assessment on the Recovery of Pectin and Phenolic Fractions from Aqueous and DES Extracts Obtained from Melon Peels

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThis work evaluates the purification of melon peel extracts obtained by two eco-friendly methods: autohydrolysis and sodium acetate/urea/water extraction (1:3:1.6), an alkaline deep eutectic solvent (DES). For that, sequential ethanol precipitation and resin adsorption/desorption stages were proposed for the separate recovery of the pectic and phenolic fractions. In order to screen the optimal purification conditions, in a first step, the effect of ethanol concentrations (from 70 to 85%) on the precipitation of pectic oligosaccharides was assayed. Subsequently, the influence of the selected resin (Amberlite XAD4, XAD16HP and XAD7HP), liquid/resin ratios, and desorption sequences (varying ethanol concentrations and pH) on the phenolic compounds was also studied. The highest pectin yields were achieved with 85% ethanol: 16.11 and 18.05 g pectin/100 g water-insoluble solids (WIS) for autohydrolysis and DES extracts, respectively. All pectins presented a galacturonic acid content of about 45%, while autohydrolysis pectin presented a higher amount of neutral sugar side chains. The presence of low methoxyl GalA and both linear and branched OGalA with DP from 2 to 20 was also confirmed by FTIR and HPAEC-PAD analysis, respectively. Concerning the phenolic fraction, the resin adsorption and desorption steps at the selected conditions (XAD4 resin, liquid/resin ratio of 2 mL/g, eluted with 50% ethanol thrice) resulted in 79.55 and 4.08 mg GAE/g non-volatile content (NVC) for autohydrolysis and DES extracts, respectively, with improved antioxidant capacity. Moreover, some phenolic acids (protocatechuic and ferulic acids) and flavonoids (orientin, vitexin and naringenin) were quantified in the extracts by HPLC–PDA-MS/MS.Agencia Estatal de Investigación | Ref. RYC2018-026177-IXunta de Galicia | Ref. ED431C 2018/47Xunta de Galicia | Ref. reference ED481A-2018/300Xunta de Galicia | Ref. ED431F 2020/0

Evaluation of strategies for enhanced bioethanol production from melon peel waste

Financiaciado para publicación en acceso aberto: Universidade de Vigo/CISUGMelon peels can be a low-cost raw material for the production of bioethanol due to its high worldwide production and contents in cellulose, protein and minerals. In this work, several strategies were proposed for this purpose. Centrifugation of the raw material and autohydrolysis of the washed solid were used as pretreatment for the recovery of a sugar rich juice and a glucan rich solid, respectively. The enzymatic hydrolysis of the autohydrolysis spent solid was studied by response surface assessment. High glucose concentrations (35.15 g/L after 24 h) and yields were obtained operating at a liquid solid ratio of 10 g/g and cellulase to solid ratio of 17.5 FPU/g. In the selected conditions, the simultaneous saccharification and fermentation (SSF) of the solid was studied using the juice (virgin and concentrated) in the formulation of the media. Moreover, the separate fermentation of the juice (virgin and concentrated) was also evaluated, as well as a pre-fermentation followed by SSF. Finally, several scenarios were proposed, achieving the maximum bioethanol production by SSF and separate juice fermentation (17.84 g/100 g melon peel), and the maximum concentration by SSF using concentrated juice in the formulation of the medium (56.24 g/L).Xunta de Galicia | Ref. GRC ED431C 2018/47Xunta de Galicia | Ref. ED431F 2020/03Ministerio de Economía y Competitividad | Ref. RYC2018- 026177-IXunta de Galicia | Ref. ED481A-2018/30

Potato peels waste as a sustainable source for biotechnological production of biofuels: Process optimization

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGPotato peel waste (PPW) is a starchy by-product generated in great amounts during the industrial processing of potatoes. It can be used as a low cost alternative, and renewable feedstock for the production of second generation bioethanol. In order to intensify this process, Saccharomyces cerevisiae Ethanol Red®, a robust and thermotolerant yeast strain, was selected and two experimental designs and response surfaces assessment were conducted to enable very high gravity fermentations (VHGF) using PPW as feedstock. The first one focused on the optimization of the liquefaction and enzymatic hydrolysis stages, enabling a maximum ethanol concentration of 116.5 g/L and a yield of 80.4 % at 72 h of fermentation; whereas, the second one, focus on the optimization of the pre-saccharification and fermentation stages, which further increased process productivity, leading to a maximum ethanol concentration of 108.8 g/L and a yield of 75.1 % after 54 h of fermentation. These results allowed the definition of an intensified pre-saccharification and simultaneous saccharification and fermentation (PSSF) process for ethanol production from PPW, resorting to short liquefaction and presaccharification times, 2 h and 10 h respectively, at an enzyme loading of 80 U/g PPW of Viscozyme and 5 UE/g PPW of SAN Super and a higher fermentation temperature of 34 ◦C due to the use of a thermotolerant yeast. Overall, with these conditions and solely from PPW without any supplementation, the outlined PSSF process allowed reaching a high ethanol concentration and yield (104.1 g/L and 71.9 %, respectively) standing at high productivities with only 54 h of fermentation.Xunta de Galicia | Ref. ED431F 2020/03Xunta de Galicia | Ref. GRC ED431C 2022/08Xunta de Galicia | Ref. GRC ED431C 2021/46Ministerio de Economía y Competitividad | Ref. PID2020-116717RB-I00Ministerio de Economía y Competitividad | Ref. PID2019- 110031RB-I00Ministerio de Economía y Competitividad | Ref. RYC2018-026177-IXunta de Galicia | Ref. UIDB/ 04469/2020Fundação para a Ciência e a Tecnologia | Ref. UIDB/ 04469/202

Eco-friendly strategy for the joint valorization of invasive macroalgae and fast-growing wood to produce advanced biofuels

A novel sustainable scheme to jointly valorize Sargassum muticum (Sm) and Paulownia wood (PW) was proposed in this work, employing the advanced environmentally friendly microwave-assisted autohydrolysis (MA) as pretreatment. Sm is an invasive macroalga that has been drastically spread in the Atlantic coast of Europe, causing environmental damage. Conversely, Paulownia elongata x fortunei is a fast-growing biomass with a high biomass production and potential for biofuels production. Thus, the concomitant valorization of both biomasses may lead to benefits related to environmental protection and bioeconomy. A sequential approach was proposed: first stage of glucose production from Sm (treated by MA and enzymatic hydrolysis to obtain a glucose-rich liquor), and second stage with MA-pretreated PW followed by saccharification and fermentation, employing in this process the glucose rich solution obtained from algae, to obtain simultaneously second and third generation bioethanol. These approaches enabled to add the ethanol production from both biomasses, leading to up to 45.2 g ethanol/L (70% ethanol yield), boosting ethanol titers compared to using only one biomass (up to 27.8 g/L) and confirming the benefits of combining MA-processed biomass. Furthermore, up to 87% of the energy may be recovered, reflecting a suitable approach within an integrated strategy.Agencia Estatal de Investigación | Ref. PID2019-110031RB-I00Agencia Estatal de Investigación | Ref. CNS2022-136095Xunta de Galicia | Ref. ED431C 2017/62-GRCXunta de Galicia | Ref. ED481B-2022-020Agencia Estatal de Investigación | Ref. RYC2018-026177-IAgencia Estatal de Investigación | Ref. RYC2020-030690-IUniversidade de Vigo/CISU

Assessment of deep eutectic solvents (DES) to fractionate Paulownia wood within a biorefinery scheme: Cellulosic bioethanol production and lignin isolation

Five deep eutectic solvents (DES) were evaluated to disrupt Paulownia wood structure to produce bioethanol and lignin. The DES formulated with choline chloride:lactic acid provided the most promising result. Temperature (110–130 ◦C), residence time (30–120 min), molar ratio (1:2–1:9), and liquid-to-solid ratio (8–15 mL/g) were optimized for cellulose recuperation (93% retained in the solid phase) and lignin removal (94% delignification yield). The spent solid was used for bioethanol production, achieving up to 43.6 g ethanol/L (89.7% ethanol yield). Lignin (84% of purity) was isolated from the black liquor and thoroughly characterized by FTIR, 1H NMR, TGA-DTG and SEM, while the liquor after lignin precipitation was chemically characterized for monomers/oligomers, total phenolic content, antioxidant activity and phytochemical profile (highlighting the presence of 25.06, 10.21 and 2.51 mg of syringaldehyde, vanillin and 3,4-dihydroxibenzoic acid per g of initial biomass). Overall, this study show that DES pre-treatment is a promising strategy for simultaneous lignin extraction and cellulose digestibility enhancement.Interreg | Ref. S1/1.1/ E0116Xunta de Galicia | Ref. ED431C 2021/46-GRCXunta de Galicia | Ref. ED481B-2022–020Agencia Estatal de Investigación | Ref. PID2019–110031RB-I00Ministerio de Universidades | Ref. FPU20/02385Universidade de Vigo/CISUGAgencia Estatal de Investigación | Ref. RYC2018–026177-

Microwave-assisted extraction of hemicellulosic oligosaccharides and phenolics from Robinia pseudoacacia wood

Financiaciado para publicación en acceso aberto: Universidade de Vigo/CISUGMicrowave-assisted autohydrolysis is an environmentally friendly intensification technology that permits the selective solubilization of hemicelluloses in form of oligosaccharides in a short time and with low energy consumption. The purpose of this work was to evaluate the suitability of microwave-assisted autohydrolysis to produce oligosaccharides and phenolics with potential prebiotic and antioxidant activities from Robinia pseudoacacia wood. The influence of treatment time (0–30 min) and temperature (200–230 ◦C) on oligosaccharide production was studied and conditions of 230 ◦C and 0.25 min resulted in maximum content of xylooligosaccharides (7.69 g XO/L) and more efficient energy consumption. Furthermore, under those conditions, liquors showed high contents of phenols (80.28 mg GAE/g of RW) and flavonoids (44.51 RE/g) with significant antioxidant activities (112.07 and 102.30 mg TE/g, measured by ABTS and FRAP tests, respectively). Additionally, the solubilized hemicelluloses were structurally characterized by HPAEC-PAD, MALDI-TOF-MS, FTIR and TGA/DSC, and HPLC-ESI-MS analysis allowed the tentative identification of 17 phytochemicals.Ministerio de Economía y Competitividad | Ref. PID2019-110031RB-I00Xunta de Galicia | Ref. ED431C 2017/62-GRCMinisterio de Ciencia e Innovación | Ref. FPU21/02446Ministerio de Ciencia e Innovación | Ref. PRE 2020 093359Ministerio de Ciencia e Innovación | Ref. RYC2018-026177-IXunta de Galicia | Ref. ED481B-2022-02

Synergetic effect of hydrothermal and deep eutectic solvents (DES) pretreatments on Robinia wood fractionation for the manufacture of bioethanol and cellulose nanocrystals

This study dealt with the use of environmentally friendly processes based on microwave-assisted autohydrolysis (MAA) and deep eutectic solvents (DES) for the selective fractionation of Robinia pseudoacacia wood (RW) within a biorefinery approach. MAA enabled the recovery of 76% of hemicelluloses in the form of oligomers. Afterwards, different conditions were assessed for the optimal delignification of RW with the DES choline chloride combined with lactic acid reaching delignification ratios up to 86%. Two different methods were accomplished to valorize the cellulosic-rich solid fraction after delignification: (i) bioethanol via enzymatic-fermentative pathway (attaining 53.3 g ethanol/L, about 83% of ethanol yield), and (ii) cellulose nanocrystals (length of 27–550 nm, width of 2–12 nm). Hence, this study presents a novel multiproduct biorefinery to selectively separate the main components of RW and valorize its cellulosic fraction using eco-friendly proceduresUniversidade de Vigo/CISUGMinisterio de Economía| Ref. PID2019-110031RB-I00Xunta de Galicia | Ref. ED431C 2017/62-GRCMinisterio de Ciencia, Innovación y Universidades | Ref. FPU21/02446Ministerio de Ciencia, Innovación y Universidades | Ref. PRE2020-093359Ministerio de Ciencia, Innovación y Universidades | Ref. RYC2018-026177-IXunta de Galicia | Ref. ED481B-2022-02

Valorization of hop (Humulus lupulus L.) pruning to produce valuable compounds using two biorefinery strategies: Conventional processing and microwave-assisted autohydrolysis

The beer industry produces a significant quantity of residues, including hop pruning from the Humulus lupulus L. plant. In this work, two alternative schemes of biorefinery were evaluated for the first time for valorization of this residue. A conventional processing, involving the water extraction of compounds (110 ◦C for 30–60 min), was proposed to obtain phenolic compounds, followed by weak acid treatment to optimize the hemicelluloses solubilization. Alternatively, innovative processing, based on autohydrolysis assisted by microwave was also evaluated for the co-extraction of antioxidants and oligosaccharides. Results obtained from these biorefineries showed that after 30 min of aqueous extraction phenols (33.86 mg GAE/g raw material) and flavonoids (42.50 mg RE/g raw material) were successfully solubilized with an antioxidant activity of 6.09, 43.56, and 29.79 mg TE/g raw material using the DPPH, ABTS, and FRAP methods, respectively. The second stage of conventional process (123.5 ◦C; 1.69 % HCl; 59.6 min) yielded the highest values of xylooligosaccharides and xylose (16.38 g/L) and glucan content (53.25 %). Alternatively, 5.50 g/L of xylooligosaccharides and xylose were obtained along with antioxidant phenolics measuring 31.74 mg GAE/g raw material and 61.06 mg RE/g raw material, using microwave-assisted autohydrolysis (200 ◦C for 5 min). The antioxidant activity of these bioactive compounds was 20.80, 29.82, and 44.01 mg TE/g raw material for the DPPH, ABTS, and FRAP assays, respectively. Overall, this study shows the feasibility of hop pruning processing under two biorefinery schemes, in which between 10.32 and 17.11 g of phenolic compounds and xylan derivatives per 100 g of raw material can be obtained, with high potential to be used in the pharmaceutical, food or chemical industriesUniversidade de Vigo/CISUGAgencia Estatal de Investigación | Ref. TED2021–132088B-I00European Comission | Ref. NEWPOWER, S1/1.1/E0116Xunta de Galicia | Ref. ED431C 2021/46-GRCAgencia Estatal de Investigación | Ref. PID2022-138458OB-I00Agencia Estatal de Investigación | Ref. FPU20/02385Agencia Estatal de Investigación | Ref. RYC2018–026177-IXunta de Galicia | Ref. ED481B-2022–02

Recuperacion de compostos bioactivos procedentes de podas de vide mediante o uso de disolventes intelixentes

Neste traballo investigouse a obtención de compostos antioxidantes a partir de podas da vide mediante extracción sólido-líquido utilizando solventes eutécticos profundos (DES) como un medio para desenvolver procesos de separación sostibles. A partir dunha selección preliminar de sete Deep Eutectic Solvents (DES) diferentes, seleccionouse unha combinación a base de glicerina-glicina-auga como sistema máis efectivo para recuperar compostos fenólicos a partir desta biomasa residual. Posteriormente, avaliouse o efecto de diferentes parámetros operativos como a temperatura (T), tempo (t), contido en auga e relación líquido-sólido (RLS) para determinar as condicións óptimas de extracción para recuperar antioxidantes naturais en termos de contido fenolóxico total (TPC), flavonoides (TFC) e actividade antioxidante dos extractos. As condicións óptimas (T = 70 ºC, t = 45 min, 40 % de auga e RLS = 15 mL/g) permitiron a recuperación dun alto nivel de compostos fenólicos (TPC = 27,49 mg GAE/g biomasa) e de flavonoides (TFC = 40,74 mg RE/g biomasa); así como unha notable actividade antioxidante (29,76; 36,09 e 20,51 mg TE/g biomasa para os ensaios de DPPH, ABTS e FRAP, respectivamente)