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Special Issue "Biorefinery Based on Olive Biomass"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "Bio-Energy".

Deadline for manuscript submissions: 30 September 2019.

Special Issue Editor

Guest Editor
Prof. Dr. Eulogio Castro

Department of Chemical, Environmental and Materials Engineering and Center for Advanced Studies in Energy and Environment, Universidad de Jaén, Campus Las Lagunillas, 23071 Jaén, Spain
Website 1 | Website 2 | E-Mail
Interests: biomass valorization; agricultural residues; biofuels; bioactive compounds

Special Issue Information

Dear Colleagues,

Olive tree cultivation is gaining an increased interest worldwide due to the health benefits of olive oil consumption. Currently, more than eleven million hectares of olive trees are spread in sixty countries, with those in the Mediterranean basin as the main olive oil producers. As a consequence of the production of olive oil, a huge amount of biomass is generated yearly, coming from two different origins. On the one hand, pruning of olive trees produces a great deal of biomass that must be eliminated from cultivation fields. On the other hand, the olive oil production process is also responsible for the generation of a number of biomasses, such as olive leaves, pits, pomace and even olive mill waste water, all of which must be adequately handled. All these biomasses can be exploited as raw material for a number of biocompounds productions, under the biorefinery scheme. This Special Issue of Bioenergies aims at summarizing the recent research developed around these different biomasses, along with procedures, methods and configurations to obtain a wide range of bioproducts, including, but not limited to biofuels, lignin, natural antioxidants, biobased compounds, fermentable sugars, etc.

Articles focusing on all areas considering olive-derived biomass are welcome, such as resource quantification, pretreatment strategies, enzymatic hydrolysis, fermentation configurations, inhibitor effects and treatments, microorganism performance, product applications, and so on.

Prof. Dr. Eulogio Castro
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • biomass from olive trees
  • pretreatment
  • fermentable sugars production
  • bioproducts
  • lignin extraction and applications

Published Papers (5 papers)

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Research

Open AccessArticle
Ultrasound-Assisted Extraction as a First Step in a Biorefinery Strategy for Valorisation of Extracted Olive Pomace
Energies 2019, 12(14), 2679; https://doi.org/10.3390/en12142679
Received: 29 May 2019 / Revised: 4 July 2019 / Accepted: 10 July 2019 / Published: 12 July 2019
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Abstract
Currently, interest in finding new feedstock as sources of natural food antioxidants is growing. The extracted olive pomace (EOP), which is an agro-industrial residue from the olive pomace extracting industries, is generated yearly in big amounts, mainly in the Mediterranean countries. EOP was [...] Read more.
Currently, interest in finding new feedstock as sources of natural food antioxidants is growing. The extracted olive pomace (EOP), which is an agro-industrial residue from the olive pomace extracting industries, is generated yearly in big amounts, mainly in the Mediterranean countries. EOP was subjected to an ultrasound assisted extraction with ethanol-water mixtures. The effect of main parameters, such as ethanol concentration (30–70% v/v), ultrasound amplitude (20–80%), and extraction time (5–15 min), on the extraction of antioxidant compounds was evaluated according to a Box–Behnken experimental design. The antioxidant capacity of the resulting extracts was determined by measuring their content in total phenolic compounds (TPC) and flavonoids (TFC), as well as their antioxidant activity by DPPH, ferric reducing antioxidant power (FRAP), and ABTS assays. Considering the simultaneous maximization of these five responses, the optimal conditions were found to be 43.2% ethanol concentration, 70% amplitude, and 15 min. The ultrasound assisted extraction of EOP under these optimized conditions yielded an extract with a phenolic and flavonoid content (per gram of EOP) of 57.5 mg gallic acid equivalent (GAE) and 126.9 mg rutin equivalent (RE), respectively. Likewise, the values for DPPH, ABTS, and FRAP assay (per gram of EOP) of 56.7, 139.1, and 64.9 mg Trolox equivalent, respectively were determined in the optimized extract. Full article
(This article belongs to the Special Issue Biorefinery Based on Olive Biomass)
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Graphical abstract

Open AccessFeature PaperArticle
Determination of the Lignocellulosic Components of Olive Tree Pruning Biomass by Near Infrared Spectroscopy
Energies 2019, 12(13), 2497; https://doi.org/10.3390/en12132497
Received: 30 May 2019 / Revised: 25 June 2019 / Accepted: 26 June 2019 / Published: 28 June 2019
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Abstract
The determination of chemical composition of lignocellulose biomass by wet chemistry analysis is labor-intensive, expensive, and time consuming. Near infrared (NIR) spectroscopy coupled with multivariate calibration offers a rapid and no-destructive alternative method. The objective of this work is to develop a NIR [...] Read more.
The determination of chemical composition of lignocellulose biomass by wet chemistry analysis is labor-intensive, expensive, and time consuming. Near infrared (NIR) spectroscopy coupled with multivariate calibration offers a rapid and no-destructive alternative method. The objective of this work is to develop a NIR calibration model for olive tree lignocellulosic biomass as a rapid tool and alternative method for chemical characterization of olive tree pruning over current wet methods. In this study, 79 milled olive tree pruning samples were analyzed for extractives, lignin, cellulose, hemicellulose, and ash content. These samples were scanned by reflectance diffuse near infrared techniques and a predictive model based on partial least squares (PLS) multivariate calibration method was developed. Five parameters were calibrated: Lignin, cellulose, hemicellulose, ash, and extractives. NIR models obtained were able to predict main components composition with R2cv values over 0.5, except for lignin which showed lowest prediction accuracy. Full article
(This article belongs to the Special Issue Biorefinery Based on Olive Biomass)
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Open AccessArticle
Optimization of Oleuropein and Luteolin-7-O-Glucoside Extraction from Olive Leaves by Ultrasound-Assisted Technology
Energies 2019, 12(13), 2486; https://doi.org/10.3390/en12132486
Received: 29 May 2019 / Revised: 20 June 2019 / Accepted: 27 June 2019 / Published: 28 June 2019
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Abstract
The olive orchard cultivation in Mediterranean countries results in huge amounts of lignocellulosic biomass residues. One of the main residues are olive leaves. Olive leaves contain high concentrations of bioactive antioxidant compounds like oleuropein and luteolin-7-glucoside. The production of biactive compounds from olive [...] Read more.
The olive orchard cultivation in Mediterranean countries results in huge amounts of lignocellulosic biomass residues. One of the main residues are olive leaves. Olive leaves contain high concentrations of bioactive antioxidant compounds like oleuropein and luteolin-7-glucoside. The production of biactive compounds from olive leaves requires treatments capable of breaking the lignocellulosic structure. Current research focuses on use of inexpensive, quick, and not harmful to the environment treatments, searching a more simplified large-scale operation approach. Recently, advances in applied chemistry have led to possible new emerging industrial techniques like ultrasound-assisted extraction (UAE). This technology is a promising candidate as a green treatment solution for olive leaves utilization in a biorefinery. However, this application goes through prior optimization of technique and operating conditions. The goal of this study was to optimize the extraction of oleuropein and luteolin-7-glucoside from olive leaves through an investigation of the influence of key factors of ultrasound-assisted extraction using an experimental central composite design, in comparison with conventional Soxhlet extraction. The highest extraction efficiency and antioxidant capacity were obtained under optimal increment of temperature and amplitude conditions (40 °C and 30%, respectively). Values for oleuropein, luteolin-7-glucoside were 69.91 g/kg and 1.82 g/kg, respectively. Full article
(This article belongs to the Special Issue Biorefinery Based on Olive Biomass)
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Open AccessArticle
Long-Term Evaluation of Mesophilic Semi-Continuous Anaerobic Digestion of Olive Mill Solid Waste Pretreated with Steam-Explosion
Energies 2019, 12(11), 2222; https://doi.org/10.3390/en12112222
Received: 23 May 2019 / Revised: 7 June 2019 / Accepted: 10 June 2019 / Published: 11 June 2019
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Abstract
Steam-explosion is a promising technology for recovering phenolic compounds from olive mill solid waste (OMSW) due to its high impact on the structure of the fibre. Moreover, the recovery of the phenols, which are well-known microbial inhibitors, could improve the subsequent biomethanization of [...] Read more.
Steam-explosion is a promising technology for recovering phenolic compounds from olive mill solid waste (OMSW) due to its high impact on the structure of the fibre. Moreover, the recovery of the phenols, which are well-known microbial inhibitors, could improve the subsequent biomethanization of the dephenolized OMSW to produce energy. However, there is a considerable lack of knowledge about how the remaining phenolic compounds could affect a long-term biomethanization process of steam-exploded OMSW. This work evaluated a semi-continuous mesophilic anaerobic digestion of dephenolized steam-exploited OMSW during a long operational period (275 days), assessing different organic loading rates (OLRs). The process was stable at an OLR of 1 gVS/(L·d), with a specific production rate of 163 ± 28 mL CH4/(gVS·d). However, the increment of the OLR up to 2 gVS/(L·d) resulted in total exhaust of the methane production. The increment in the propionic acid concentration up to 1486 mg/L could be the main responsible factor for the inhibition. Regardless of the OLR, the concentration of phenolic compounds was always lower than the inhibition limits. Therefore, steam-exploited OMSW could be a suitable substrate for anaerobic digestion at a suitable OLR. Full article
(This article belongs to the Special Issue Biorefinery Based on Olive Biomass)
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Open AccessArticle
Monitoring the Bioactive Compounds Status in Olea europaea According to Collecting Period and Drying Conditions
Energies 2019, 12(5), 947; https://doi.org/10.3390/en12050947
Received: 4 January 2019 / Revised: 4 March 2019 / Accepted: 6 March 2019 / Published: 12 March 2019
PDF Full-text (2727 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Polyphenols and triterpenoids in olive have relevant importance both in the physiology of the plant and the nutritional and biological value of its products. Olive leaf extracts are of special interest for their numerous health-promoting properties. The present research is investigating the occurrence [...] Read more.
Polyphenols and triterpenoids in olive have relevant importance both in the physiology of the plant and the nutritional and biological value of its products. Olive leaf extracts are of special interest for their numerous health-promoting properties. The present research is investigating the occurrence of phytochemicals in supercritical fluid extracts from leaves with regard to collection time and drying temperature. The phytochemical profiles of the olive leaf extracts were determined by reversed-phase high-performance liquid chromatography (HPLC) coupled to electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) detection. The main extracted phytochemicals were phenols and terpenoids. A significant variation in the amounts of the different components was observed as a function of the different drying temperature and collecting time (p < 0.05). Among samples, the maximal contents of polyphenols and secoiridoid derivatives were found in the extracts from olive leaves collected in November and dried at 120 °C, whereas triterpenoids showed the highest content in fresh leaves collected in August. Full article
(This article belongs to the Special Issue Biorefinery Based on Olive Biomass)
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