Optimization of Microwave-Assisted Water Extraction to Obtain High Value-Added Compounds from Exhausted Olive Pomace in a Biorefinery Context

Abstract

Microwave-assisted water extraction (MAWE) was evaluated to obtain the valuable bioactive compounds hydroxytyrosol and mannitol from exhausted olive pomace (EOP). The influence of the operational parameters solid loading (3–15%, w/v), temperature (40–100 °C), and extraction time (4–40 min) was studied using an experimental design. The optimized conditions maximizing their joint extraction were 12% w/v solid loading, 100 °C temperature, and 16 min. It was possible to solubilize 5.87 mg of hydroxytyrosol/g EOP and 46.70 mg mannitol/g EOP. The extracts were also further characterized by liquid chromatography–mass spectrometry, which detected other hydroxytyrosol derivatives such as oleacein, verbascoside, and oleuropein. Moreover, the applied MAWE conditions promoted the co-extraction of proteinaceus material, which was also evaluated. In order to carry out an integral valorization of this waste, the extracted EOP solid was further evaluated chemically and microscopically before recovering the bioactive triterpenes. In particular, maslinic acid and oleanolic acid were obtained, 9.54 mg/g extracted solid and 3.60 mg/g extracted solid, respectively. Overall, MAWE can be applied as a first stage in the fractionation of EOP to support its valorization in a biorefinery framework.

Towards the Integral Valorization of Olive Pomace‐Derived Biomasses through Biorefinery Strategies

“…During its combustion, particles that are harmful to human health and the environment are emitted 56. This fact has prompted looking for new valorization ways, e.g., to obtain fermentable sugars 22, 23, 55, ethanol 57, xylitol 58, polygalacturonase and fatty acids 59, proteins 24, lignin, and bioactive compounds 22, 23, 55.…”

“…It has nonhygroscopic properties, making it a potential excipient for moisture‐sensitive drugs 66. Also, it has the potential to be applied for the treatment of diseases such as Parkinson's disease, cystic fibrosis, migraines, and renal insufficiency 22.…”

“…Integrating the extraction of these biocompounds together with obtaining bioenergy, biofuels, and/or other value‐added chemicals is a subject of current studies 21–24. This means applying biorefinery schemes that provide value to olive pomace‐derived biomass and the transition towards a circular (bio)economy based on sustainable principles and green chemistry.…”

Hydrothermal Treatment of Biomass Feedstocks for Sustainable Production of Chemicals, Fuels, and Materials: Progress and Perspectives

“…Microwave-assisted hydrothermal extraction (MHE) is widely used in biorefinery because it promotes disintegration of microalgal cells which often contain polymers such as algaenan and sporopollenin which are difficult to degradation with chemical treatment . MHE offers several advantages over conventional methods including the increase of yield and purity of bioactive compounds, reduction of extraction times, energy consumption, and solvent requirement. , The properties of extracted compounds can be controlled by the extraction conditions (solid loading, temperature, and time). , MHE is used for the extraction of bioactive compounds (e.g., solanesol and cembranoids) from lignocellulosic biomass (rich in hemicellulose, cellulose, and lignin) for applications in medicines and in seed oil production for biofuels. ,, Tsubaki et al and Yuan et al used different types of green algae (e.g., Ulva meridionalis , Ulva ohnoi , Monostroma latissimum , or Ulva prolifera ) for the extraction of sulfated polysaccharides/polysaccharides using the MHE process. The yield of sulfated polysaccharides varied between 36.5 and 53.1% .…”

“…552,553 The properties of extracted compounds can be controlled by the extraction conditions (solid loading, temperature, and time). 554,555 MHE is used for the extraction of bioactive compounds (e.g., solanesol and cembranoids) from lignocellulosic biomass (rich in hemicellulose, cellulose, and lignin) for applications in medicines and in seed oil production for biofuels. 540,556,557 Tsubaki et al 558 and Yuan et al 540 used different types of green algae (e.g., Ulva meridionalis, Ulva ohnoi, Monostroma latissimum, or Ulva prolifera) for the extraction of sulfated polysaccharides/polysaccharides using the MHE process.…”