Extraction of ferulic acid and feruloylated arabinoxylo-oligosaccharides from wheat bran using pressurized hot water

Producción CientíficaPressurized water was tested as solvent for the hydrolysis and extraction of Ferulic acid (FA) and feruloylated arabinoxylooligosaccharides (F-AXOS) from destarched wheat bran (DWB). Results were dependent on the severity factor of the process (combination of temperature and time), obtaining the maximum extraction yields at 200°C and 3.5 min. 78% of the total FA was successfully extracted, being 17% in its free form and the rest, covalent ester-bounded to arabinoxylans. Under such conditions, 80% of the arabinoxylans are extracted with a degree of FA esterification of 1.34 g FA/100 g AXOS, and an average molecular weight of 1,3·104 Da. Pressurized Microwave Assisted Extraction was also studied to evaluate potential intensification of the process using microwaves. However, no significant differences were observed with the microwave heating. Residual solid after extraction was mainly composed by lignin and cellulose (56% and 21%, respectively) showing that hot compressed water technology can be integrated in the first steps of a biorefinery for the total valorization of the wheat bran.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project CTQ2015-64892-R

Understanding biomass fractionation in subcritical & supercritical water

Producción CientíficaBiomass fractionation into its individual building blocks poses a major challenge to the biorefinery concept. The recalcitrance of the lignocellulose matrix and the high crystallinity of cellulose make typical feed stocks difficult to separate into their components. Hydrothermal processing fractionates biomass by its hydrolysis. However, a deep knowledge of hydrolysis principles is required since an inappropriate selection of the operating parameters such as an excessive temperature and a long residence times causes dramatic selectivity losses. This review is divided in four main sections which present the fundamentals of lignocellulosic biomass fractionation in hemicelluloses, cellulose and lignin. As the biomass structure plays an important role, a section to study the extraction of the linked phenols that joint lignin and hemicelluloses is included.Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA040U16)Ministerio de Economía, Industria y Competitividad - FEDER (Proyect CTQ2013-44143-R)Ministerio de Economía, Industria y Competitividad - FEDER (Proyect CTQ2016-79777-R

10th World Congress of Chemical Engineering,

Wheat bran is an important by-product of the cereal milling industry and it has a great potential as raw material in a biorefinery. Wheat bran contains many important bioactive phenolic compounds, such as ferulic acid (FA), phytic acid, caffeic acid and flavonoids that can be recovered in a first step of a cereal biorefinery to increase economical benefit of the whole process. FA is the most abundant phenolic acid in the wheat bran, and it exhibits a number of potential applications such as natural antioxidant, food preservative/antimicrobial agent, anti-inflammatory agent, photoprotectant, and as precursor of vanillin (food flavor). FA seems to be part of the cell wall bounded via ester linkages to the structural polysaccharides, while dimers of ferulic acid can serve to cross-link hemicelluloses. Ferulic acid is unstable and can be oxidized in high temperature and it could be denature and reduced by using alkaline-hydrolysis. Release of FA from plant material is typically facilitated by alkaline and enzymatic hydrolysis. Alkaline-hydrolysis cannot be considered a green technology, is poorly selective and solvent consuming. Enzymatic-hydrolysis requires cocktails of enzymes (amylases, xylanases, proteases, feruloyl esterases) combined with bran pre-treatment and exhibits economical drawbacks and low extraction yield per unit of enzyme. The challenge is, therefore, to intensify the process by using green and short time techniques with high hydrolysis capacity to recover selectively the maximum amount of free FA and preserving the antioxidant activity of the extract. In this work, we present and discuss a strategy to maximize the recovering of free FA from wheat bran by using microwaves and subcritical water. This study presents the effect of various factors in a Microwave-Assisted-Extraction (MAE) with water: time, temperature and solvent/solid ratio, using Box-Benhken experimental design. MAE of wheat bran at 220ºC and 1 minute leads to the recovery of ca. 80% of the FA, that is a really high yield compared to that reported in the literature for enzymatic hydrolysis (15-35%) [1]. However, more than 70% of FA remains bounded to the cell compounds extracted under such conditions. Subcritical water in the range has been evaluated to complete the release of free FA. Temperatures in the range 250-320 ºC and time from 1 to 10 min have been studied at 150 barg and discussed using the severity factor. Under such conditions dissociation of water is very important, and hydroxyl groups act to the ester bond breakage. Results are discussed in terms of total FA extraction yield, Free FA extraction yield, TOC and total phenolic content and antioxidant capacity of the final hydrolysate.Proyecto CTQ2015-64892-R (MINECO/FEDER

12th International Conference on Renewable Resources and Biorefineries (RRB-12)

Wheat bran can be considered as a feedstock for future biorefineries, due to the enormous quantities arising in the milling industry and its specific properties. It has a high content of nutritionally valuable and technologically desirable compounds. Development of efficient processes for the isolation of such high-value compounds could represent a real cost effectiveness to the whole process. Ferulic acid (FA) is the most abundant hydroxycinnamic acid found in wheat bran and is of considerable interest due to its antioxidant properties. Its extraction from wheat bran represents a great opportunity to add value. The main inconvenient is that the major part of the FA is in an insoluble bound form, esterified to the arabinoxylans (AX) and other cell wall structural components (≈92%). Hence, new processes are required to break these bonds in order to recover it in high quantities. In this study, different strategies have been tested for ferulic acid recovery, i) extraction with pressurized aqueous ethanol mixtures, ii) microwave-assisted extractions and iii) ultrafast supercritical water extraction. Operational conditions have been studied and optimized for these three extraction processes to maximize the FA extraction yield. The studied variables were: the ethanol:water content in the mixture (20-50-80%), temperature (130-145-160ºC) and extraction time (20-40-60min) in the pressurized solvent extraction process, extraction time (1-10 min) in the microwave-assisted extraction and time (0.15-0.3 s) in the ultrafast supercritical water extraction process. The analysis of the FA profile in the wheat bran use as raw material consists in the quantification of its free, soluble bound and insoluble bound forms. An alkaline hydrolysis is performed in order to release the bound forms, and finally, they are quantified as free ferulic acid by HPLC analysis. In the samples obtained in each experiment, the FA content and the total phenolic content (TPC) are analysed. The TPC analysis is performed by the Folin-Ciocalteu method.CTQ2015-64892-R (MINECO/FEDER)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA040U16