Sustainable Environmental Management and Valorization Options for Olive Mill Byproducts in the Middle East and North Africa (MENA) Region

Biotechnological Innovations Unleashing the Potential of Olive Mill Wastewater in Added-Value Bioproducts

Byproducts and wastes from the food processing industry represent an important group of wastes generated annually in large quantities. It is important to note that the amount of this waste will increase with industrialization, and effective solutions must be found urgently. Many wastes that cause environmental pollution are evaluated by their low-tech conversion into products with little economic value, such as animal feed and fertilizer. Therefore, the evaluation of food processing waste using effective recycling techniques has become an interesting subject with increasing population, ongoing biotechnological studies, and advances in technology. The conversion of food waste into biotechnological products via fermentation is a sustainable, environmentally friendly, and economical method in line with the principles of green chemistry. This approach promotes the reuse of food waste by supporting the principles of a circular economy and offers sustainable alternatives to fossil fuels and synthetic chemicals. This contributes to reducing the carbon footprint, preserving soil and water quality, and providing economic sustainability through the production of high-value products. In this study, the properties of olive mill wastewater, an important and valuable waste in the olive oil industry, its environmental aspects, and its use in biotechnological applications that integrate green chemistry are evaluated.

Monitoring the Phenolic and Terpenic Profile of Olives, Olive Oils and By-Products throughout the Production Process

Olive oil is a food of great importance in the Mediterranean diet and culture. However, during its production, the olive oil industry generates a large amount of waste by-products that can be an important source of bioactive compounds, such as phenolic compounds and terpenes, revalorizing them in the context of the circular economy. Therefore, it is of great interest to study the distribution and abundance of these bioactive compounds in the different by-products. This research is a screening focused on phytochemical analysis, with particular emphasis on the identification and quantification of the phenolic and terpenic fractions. Both the main products of the olive industry (olives, olive paste and produced oil) and the by-products generated throughout the oil production process (leaf, "alpeorujo", liquid and solid residues generated during decanting commonly named "borras" and washing water) were analyzed. For this purpose, different optimized extraction procedures were performed for each matrix, followed by high-performance liquid chromatography coupled with electrospray time-of-flight mass spectrometry (HPLC-ESI-TOF/MS) analysis. Although no phenolic alcohols were quantified in the leaf and the presence of secoiridoids was low, this by-product was notable for its flavonoid (720 ± 20 µg/g) and terpene (5000 ± 300 µg/g) contents. "Alpeorujo" presented a complete profile of compounds of interest, being abundant in phenolic alcohols (900 ± 100 µg/g), secoiridoids (4500 ± 500 µg/g) and terpenes (1200 ± 100 µg/g), among others. On the other hand, while the solid residue of the borras was the most abundant in phenolic alcohols (3700 ± 200 µg/g) and secoiridoids (680 ± 20 µg/g), the liquid fraction of this waste was notable for its content of elenolic acid derivatives (1700 ± 100 µg/mL) and phenolic alcohols (3000 ± 300 µg/mL). Furthermore, to our knowledge, this is the first time that the terpene content of this by-product has been monitored, demonstrating that it is an important source of these compounds, especially maslinic acid (120 ± 20 µg/g). Finally, the phytochemical content in wash water was lower than expected, and only elenolic acid derivatives were detected (6 ± 1 µg/mL). The results highlighted the potential of the olive by-products as possible alternative sources of a wide variety of olive bioactive compounds for their revalorization into value-added products.

HPLC-MS/MS Phenolic Characterization of Olive Pomace Extracts Obtained Using an Innovative Mechanical Approach

Olive pomace results from the production of olive oil. Even if olive pomace represents a potential environmental problem, it contains phenolic compounds, which are widely recognized for their beneficial properties for human health. In this study, an innovative and sustainable technological approach to extract phenolic compounds from fresh olive pomace, based on food-grade solvent instead of those usually adopted, is investigated. Characterization and shelf-life evaluation of the hydroalcoholic extracts obtained from the procedure developed for different industrial purposes were also carried out. The phenolic fractions of the different samples were studied with the Folin-Ciocâlteu method to quantify that the total reducing molecules and HPLC-MS/MS analysis was used to define the profile through the identification and quantification of 42 compounds, belonging to five chemical families. Regarding shelf-life, the hydroalcoholic extract showed no significant reduction in phenolic content, for both instrumental evaluations, retaining most of the phenolic compounds present in the raw material; negative attributes were not perceived by sensory evaluation. Thus, these lab-scale results can be the starting point to develop a procedure that is suitable for a real olive mill, representing a valorization strategy in a circular economy and the perspective of new business models.

Growth Response of Non-Conventional Yeasts on Sugar-Rich Media: Part 2: Citric Acid Production and Circular-Oriented Valorization of Glucose-Enriched Olive Mill Wastewaters Using Novel Yarrowia lipolytica Strains

The global market for citric acid (CA) is one of the biggest and fastest expanding markets in the food industry. The CA production employing microbial bioprocessing with efficient GRAS strains and renewable waste streams is in line with the European Union binding targets for resource efficiency, sustainable consumption-production, and low-carbon technologies. In this work, the potential of three novel wild-type Yarrowia lipolytica strains (namely LMBF Y-46, LMBF Y-47 and ACA-YC 5033) regarding the production of CA and other valuable metabolites was tested on glucose-based media, and the most promising amongst the screened strains (viz. the strain ACA-YC 5033) was cultured on glucose-based media, in which part of the fermentation water had been replaced by olive-mill wastewaters (OMWs) in a novel approach of simultaneous OMW valorization and bioremediation. In the first part of this study, the mentioned strains were cultured under nitrogen-limited conditions with commercial (low-cost) glucose employed as a sole carbon source in shake-flask cultures at an initial concentration (S0) ≈ of 50 g/L. Variable quantities of secreted citric acid (CA) and intra-cellular compounds (viz. polysaccharides and lipids) were produced. All strains did not accumulate significantly high lipid quantities (i.e., maximum lipid in dry cell weight [DCW] values ≈30% w/w were noted) but produced variable CA quantities. The most promising strain, namely ACA-YC 5033, produced CA up to c. 24 g/L, with a yield of CA produced on glucose consumed (YCA/S) ≈ 0.45 g/g. This strain in stirred tank bioreactor experiments, at remarkably higher S0 concentrations (≈110 g/L) and the same initial nitrogen quantity added into the medium, produced notably higher CA quantities, up to 57 g/L (YCA/S ≈ 0.52 g/g). The potential of the same strain (ACA-YC 5033) to bioremediate OMWs and to produce value-added compounds, i.e., yeast cells, CA, and intra-cellular metabolites, was also assessed; under nitrogen-limited conditions in which OMWs had partially replaced tap water and significant glucose concentrations had been added (S0 ≈ 100 g/L, simultaneous molar ratio C/N ≈ 285 g/g, initial phenolic compounds [Phen0] adjusted to ≈1.0 g/L; these media were similar to the OMWs generated from the traditional press extraction systems) the notable CA quantity of 60.2 g/L with simultaneous YCA/S = 0.66 g/g, was obtained in shake flasks, together with satisfactory phenolic compounds removal (up to 19.5% w/w) and waste decolorization (up to 47.0%). Carbon-limited conditions with Phen0 ≈ 1.0 g/L favored the production of yeast DCW (up to 25.3 g/L), with equally simultaneous interesting phenolic compounds and color removal. The fatty acid profile showed that cellular lipids were highly unsaturated with oleic, linoleic and palmitoleic acids, accounting for more than 80% w/w. This study proposed an interesting approach that could efficiently address the biotreatment of toxic effluents and further convert them into circular-oriented bioproducts.

Comparison of sheep and goat preferences for different forms of stoned olive cake

The objectives of this experiment were to investigate voluntary intake of stoned olive cake (SOC) in sheep and goats. The feeding experiment was carried out with a total of 10 animals consisting of five Karya yearlings and five Saanen goats (28.0 ± 2.0 and 37.0 ± 2.1 kg initial body weight (BW), respectively). Three feeds were offered as free-choice: alfalfa hay-maize silage mix (40:60 in dry matter basis), pelleted SOC, and ensiled SOC. Goats had higher (P < 0.001) dry matter (DM) and neutral detergent fiber (NDF) intakes than sheep, although digestible DM and NDF intakes were similar. Goats consumed more (P < 0.05) pelleted SOC and ensiled SOC than sheep as a percentage of total intake (29.2 and 22.4%, respectively). Both sheep and goats preferred (P < 0.001) the silage form of SOC compared to the pelleted form of SOC.

The current status and challenges of biomass biorefineries in Africa: A critical review and future perspectives for bioeconomy development

Africa benefits from diverse biomasses that are rich in high-added value materials and precursors for energy, food, agricultural, cosmetic and medicinal applications. Many African countries are interested in valorizing biomasses to develop efficient and integrated biorefinery processes and their use for local and regional economic development. Thus, this report critically reviews the current status of African biomass richness, its diversity, and potential applications. Moreover, particular attention is given to bioenergy production, mainly by biological and thermochemical conversion processes. This also includes biomass valorization in agriculture, particularly for the production of plant-based biostimulants, which are a potential emerging agri-input sector worldwide. This study points out that even though several processes for biofuel, biogas, biofertilizer and biostimulant production have already been established in Africa, their development on a larger scale remains limited. This study also reports the different socioeconomic and political aspects of biomass applications, along with their challenges, opportunities, and future research perspectives, to promote concrete technologies transferable into an industrial level.

Effect of dietary olive (Olea europea) pomace on productive performance, and physiological and meat quality parameters in Jumbo quail

High levels of dietary fiber could restrict the inclusion of olive (Olea europea L.) pomace (OP) as a source of energy and bioactive compounds in Jumbo quail (Coturnix sp.) diets. In this study, the optimum inclusion level of dietary OP on growth and carcass performance, serum biochemistry, and meat quality parameters in Jumbo quail was investigated. One-week-old Jumbo quail (350; 28.9 ± 1.29 g live-weight) were reared on a standard mash grower diet with 0 (OP0), 100 (OP10), 150 (OP15), 200 (OP20), and 250 g/kg (OP25) OP for five weeks. The experimental diets were randomly allocated to 35 pens (experimental units) with seven replicates each. Overall body weight gain in Jumbo quail fed with diets OP20 and OP25 was lower (p < 0.001) than those fed diets OP0 and OP10. Including dietary OP had no effect on the overall gain-to-feed ratio, serum biochemistry, and internal organs but linearly reduced carcass yields. Diet OP25 promoted a higher (p < 0.022) meat hue angle value than the other diets. The inclusion of OP beyond 150 g/kg compromised growth and carcass performance, and altered some meat color attributes, but had no influence on serum biochemistry, and internal organs of the Jumbo quail.

Effect of Feeding Olive Pomace Acid Oil on Dark Chicken Meat Lipid Composition, Oxidative Stability, Color, and Sensory Acceptance

This study evaluated the effect of using olive pomace acid oil (OPAO) instead of crude palm oil (PO) or refined olive pomace oil (ROPO) on lipid composition, lipid oxidation, and quality of chicken meat. Broiler chickens were fed diets with 6% of PO, ROPO, or OPAO, and deboned legs with skin were sampled. Fresh and refrigerated (commercial conditions; 7 days) chicken meat samples were assessed for fatty acid (FA) composition, tocopherol (T) and tocotrienol (T3) content, lipid oxidative stability, 2-thiobarbituric acid (TBA) values, volatile compounds, color, and sensory acceptance. Using ROPO and OPAO led to meat richer in monounsaturated FAs and OPAO to lower α-T levels compared to PO. Oxidative stability, TBA values, volatile compounds, and overall acceptance of meat were not affected by diet. Refrigeration increased TBA values and some volatile compounds' concentrations, but it did not decrease redness or consumers' overall acceptance. Therefore, the OPAO used was an adequate fat source for chicken diets at 6%, as it produced dark meat lower in saturated FAs than PO without affecting lipid oxidation or overall acceptance. According to this, upcycling OPAO as an energy source in chicken diets would be possible, which can contribute to the sustainability of the food chain.

Sustainable recovery of phenolic antioxidants from real olive vegetation water with natural hydrophobic eutectic solvents and terpenoids

Olive oil production leads to the generation of olive mill wastewater (OMWW). Due to the presence of phenolic compounds, they are difficult to process, but they represent a source of high-added value chemicals since they have antioxidant and therapeutic properties. This work has studied the extraction of phenolic compounds from a type of OMWW, olive vegetation water, which presents these compounds in a more diluted dosage than in other studied to date, to revalue this waste stream. A real olive vegetation water from a Spanish olive oil producer was used, and liquid-liquid extraction was applied. Terpenoids and terpene-based hydrophobic eutectic solvents were systematically used to extract phenolic compounds following the concentrations of tyrosol, catechol, caffeic acid, and total phenolic content. By molecular simulation with the COSMO-RS method, 4 terpenoids, and 2 eutectic solvents were selected and compared with 2 conventional solvents. The Solvent/Feed ratio in the extraction of phenolic compounds was studied, showing that the solvents with the highest extraction results were geraniol, eucalyptol, and eutectic solvent menthol + camphor, which outperformed conventional solvents methyl isobutyl ketone and diisopropyl ether. Menthol + camphor gave total phenol extraction yields of 88.73% at a Solvent/Feed ratio in volume of 0.50, surpassing all solvents tested. A solvent reuse and regeneration process was applied by back-extraction of the 4 solvents: FTIR results showed the stability of the solvents while maintaining yields in the solvent reuse process. The phenolic compounds could be concentrated in the alkaline phase to factors up to 49.3 to the initial concentration in olive vegetation water. The alkaline phases were neutralized to obtain a precipitate with a caffeic acid content of up to 26 % wt%, and a tyrosol-rich supernatant with a concentration of up to 6.54 g/L. This work proposes a process using natural solvents to extract phenolic compounds from olive vegetation water.

Treatment technologies for olive mill wastewater with impacts on plants

Olive mill wastewater (OMW), produced during olive oil production, contains high levels of salt contents, organic matter, suspended particles, and toxic chemicals (particularly phenols), which all result in increased biological and chemical oxygen demand. Olive Oil Mills' Wastes (OMW), which have dark brown color with unpleasant smell, consist mainly of water, high organic (mainly phenols and polyphenols) and low inorganic compounds (e.g. potassium and phosphorus), as well as grease. OMW components can negatively affect soil's physical, chemical, and biological properties, rendering it phytotoxic. However, OMW can positively affect plants' development when it's applied to the soil after pretreatment and treatment processes due to its high mineral contents and organic matter. There are various approaches for removing impurities and the treatment of OMW including chemical, biological, thermal, physiochemical, and biophysical processes. Physical techniques involve filtration, dilution, and centrifugation. Thermal methods include combustion and pyrolysis; biological techniques use anaerobic and aerobic techniques, whereas adsorption and electrocoagulation act as physiochemical methods, and coagulation and flocculation as biophysical methods. In contrast, combined biological treatment methods use co-digestion and composting. A comparison of the effects of both treated and untreated OMW samples on plant development and soil parameters can help us to understand the potential role of OMW in increasing soil fertility. This review discusses the impacts of untreated OMW and treated OMW in terms of soil characteristics, seed germination, and plant growth. This review summarizes all alternative approaches and technologies for pretreatment, treatment, and recovery of valuable byproducts and reuse of OMW across the world.

Circular bioeconomy for olive oil waste and by-product valorisation: Actors' strategies and conditions in the Mediterranean area

The circular economy and bioeconomy can contribute to transitioning towards more sustainable production and consumption in the olive oil sector. This article is the first to analyse multi-actor strategies and multi-level socio-economic conditions for olive oil waste and by-product valorisation in the Mediterranean area using circular bioeconomy principles. Government policies, the strategies of corporations and farmers and consumers' perceptions are discussed, and various methods are applied, such as desk reviews, case studies and quantitative and qualitative surveys. The findings show strong aspirations for improved sustainability in the olive industry. Furthermore, waste and by-product valorisation strategies foster the creation of innovative practices. However, a common regulatory framework, public financial measures, new circular business models using innovative technologies, multi-actor collaboration and increased consumer awareness of the circular economy and new olive oil waste-based products are necessary for more efficient and sustainable use of olive resources. The policy and management recommendations presented in this study may aid in improving and innovating frameworks and practices for better sustainable management of valuable olive resources.

Adsorption of rutin from olive mill wastewater using copolymeric hydrogels based on N-vinylimidazole: Kinetic, equilibrium, and thermodynamics assessments

Olive mill wastewater, also known as olive wastewater, contains biologically active components with various beneficial effects on health. The development of novel adsorbent materials for the recovery of these biologically active substances is important area of research. In this study, copolymeric hydrogels based on N-vinylimidazole (VIm), a new material that has never been used as an adsorbent in the separation of phenolic components, were synthesized. The hydrogels synthesized in this study is copolymer structures based on N-vinylimidazole (VIm) containing [2- (methacryloxy) ethyl] dimethylpentylammonium bromide (QDMAC5) in different moles. QDMAC5 was obtained by quaternization of 2- (dimethylamino) ethyl methacrylate (DMA) with 1-bromopentane (C5). The production of copolymer hydrogels was carried out by free radical solution polymerization. The syntheses were carried out only by changing the monomer composition so that the crosslinker ratio remained constant (1.2 mol%). The QDMAC5 content in the copolymers was 5, 10, 20, 30, and 50 mol%. So, the resulting structures were named PVQ-5%, PVQ-10%, PVQ-20%, PVQ-30%, and PVQ-50%, respectively. Functional group characterizations of hydrogels were made by Fourier Transform Infrared Spectrometry (FTIR). The surface of the hydrogels was analyzed by Scanning Electron Microscopy (SEM). Finally, thermogravimetric analyzes (TGA) were performed to investigate the thermal degradation behavior. The recovery of the rutin present in olive mill wastewater has been investigated as a model study. Kinetic data has been represented by the selected models (pseudo-first order, pseudo-second order, and intraparticle diffusion) convincingly (R² > 0.76), while the equilibrium findings have fitted well to Langmuir, Freundlich, and Temkin equations (R² > 0.77). Rutin adsorption process on N-vinylimidazole (VIm) based copolymeric hydrogels has been found as exothermic and spontaneous chemisorption process depending on the thermodynamic analysis.

Optimization of Autohydrolysis of Olive Pomaces to Obtain Bioactive Oligosaccharides: The Effect of Cultivar and Fruit Ripening

The valorisation of agro-industrial residues presents a challenge in obtaining economically sustainable and environmentally friendly industrial processes. Olive pomace is a by-product generated in large quantities, from olive oil extraction. This residue mostly consists of lignocellulosic materials. The aim of this study was to evaluate the potential use of extracted olive pomaces (EOP) obtained from olives with different ripening indexes (RI) and from different cultivars (Cobrançosa; RI = 2.5; 3.3 and 4.7; and Galega Vulgar; RI = 1.8; 2.9 and 4.8), to produce bioactive oligosaccharides from hemicelluloses by autohydrolysis. The hydrothermal treatment conditions were optimized by Response Surface Methodology, following a central composite rotatable design (CCRD), as a function of temperature (T: 142–198 °C) and time (t: 48–132 min), corresponding to severity factor (SF) values from 3.2 to 4.9. For all pomace samples, soluble sugar production was described by concave surfaces as a function of temperature and time. Autohydrolysis with SF equal or higher than 4.0 produced higher sugar yields, with maximum values around 180 g glucose equivalent/kg EOP for SF of 4.7 (190 °C/120 min) or 4.9 (198 °C/90 min). These values were similar for both cultivars and were not dependent on the ripening stage of the olives. Maximum oligosaccharide (OS) yields of 98% were obtained by autohydrolysis with SF of 4.0. The increase in SF to 4.9 resulted in a decrease in OS yield to 86–92%, due to the release of monomeric sugars. The monosaccharides were mostly xylose (55.8–67.7% in Galega; 50.4–69.0% in Cobrançosa liquid phases), and glucose, galactose, arabinose and rhamnose, in smaller quantities. Therefore, the production of bioactive xylo-oligosaccharides (XOS) from olive pomaces mainly depends on the hydrothermal conditions used.

Designing of pretreatment filter technique for reduction of phenolic constituents from olive-mill wastewater and testing its impact on wheat germination

Olive oil extraction produces a great volume of olive mill wastewater (OMW), which is considered a serious ecological challenge. In this study, we have designed and tested a trickling filter consisting of seven different layers of natural material, including (coarse gravel, fine gravel, lime (Ca (OH)₂), sand (SiO₂), carbon char, sponge/mesh), to treat OMW. The filter process involved physical separation, filtration, coagulation and adsorption with the removal of COD (69.8%), BOD (40.2%), Phenolic contents (90%), pH (41%), EC (41.6%) and total suspended solids (TSS) (69%). Our results have shown that treated OMW has a high potential oxidant activity. T7, Untreated OMW at 1:6 dilutions, had the strongest correlation (i.e. 0.97), while untreated OMW had the lowest IC50 (7.62 g ml^-1), which shown the best DPPH radical scavenging capabilities. While pure Untreated OMW has the maximum radical scavenging activity, 63%, treated (1:6) diluted OMW exhibits the lowest value i. e 9% when phosphomolybdate assay was done. HPLC analysis showed that the trickling filter removed the vanillic acid, caffeic acid and reduced the contents of phenolic components such as gallic acid, hydroxytyrosol, vanillin, quercetin and catechol. Filtered OMW was also tested for its germination efficacy at various dilutions (1:0, 1:2, 1:4, 1:6). A remarkable improvement in germination percentage, germination index, seedling length, seedling vigor index, promptness index, stress tolerance index (76.7%, 68.4%, 51.7%, 82.1%, 54.8%, and 66.7%, respectively) has shown the efficiency of treated OMW at 1:6 dilutions. The results from this study show the efficiency of our filter design which can be further used.

Use of Anthracophyllum Discolor and Stereum Hirsutum as a Suitable Strategy for Delignification and Phenolic Removal of Olive Mill Solid Waste

This study evaluated the use of the white-rot fungi (WRF) Anthracophyllum discolor and Stereum hirsutum as a biological pretreatment for olive mill solid mill waste (OMSW). The WRF strains proposed were added directly to OMSW. The assays consisted of determining the need to add supplementary nutrients, an exogenous carbon source or use agitation systems, and evaluating WRF growth, enzyme activity, phenolic compound removal and lignin degradation. The highest ligninolytic enzyme activity was found at day 10, reaching 176.7 U/L of manganese-independent peroxidase (MniP) produced by A. discolor, and the highest phenolic removal (more than 80% with both strains) was reached after 24 days of incubation. The confocal laser scanning microscopy analysis (CLSM) confirmed lignin degradation through the drop in lignin relative fluorescence units (RFU) from 3967 for untreated OMSW to 235 and 221 RFU, showing a lignin relative degradation of 94.1% and 94.4% after 24 days of treatment by A. discolor and S. hirsutum, respectively. The results demonstrate for the first time that A. discolor and S. hirsutum were able to degrade lignin and remove phenolic compounds from OMSW using this as the sole substrate without adding other nutrients or using agitation systems. This work indicates that it could be possible to design an in situ pretreatment of the valorization of OMSW, avoiding complex systems or transportation. In this sense, future research under non-sterile conditions is needed to evaluate the competition of WRF with other microorganisms present in the OMSW. The main drawbacks of this work are associated with both the low reaction time and the water addition. However, OMSW is seasonal waste produced in one season per year, being stored for a long time. In terms of water addition, the necessary optimization will be addressed in future research.

Biological activities and phenolic compounds of olive oil mill wastewater from Abani, endemic Algerian variety

The current study aimed to determination of cytotoxicity, antioxidant, anti-inflammatory, anti-hemolytic, and anticoagulant activities of phenolic compounds extracted from olive oil mill wastewater (OMW) issue from the cold extraction of olive oil from Khenchela eastern in Algeria. The LC–MS (liquid chromatography–mass spectrometry) results were revealed the presence of 20 phenolic compounds in the extract of OMW and mostly consisted of Kaempferol, 4,5-di-O-caffeoyquinic acid, quinic acid, and caffeic acid. The extracts possessed effective reducing power (FRAP) and high radical scavenging activity against DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS + (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) free radicals, and it inhibited cytochrome c reduction in a dose-dependent manner. They exert a protective effect on red blood cells, and they were found to exhibit the highest inhibitory effect anti-inflammatory activity using inhibition of protein denaturation (IPD) and membrane stabilizing potential (MSP) tests (80.46 ± 3.81 µg/mL and 87.43 ± 0.66 µg/mL) more than the standard used. The extract also showed the greatest anticoagulant activity in both the endogenous and exogenous routes (44.77 ± 0.25 s and 15.84 ± 0.12 s, respectively). Based on these findings, it is reasonable to infer that OMW is a good source of natural phenolic compounds with potential antioxidant, anti-inflammatory, and anticoagulant properties.

A Potential Valorization Strategy of Wine Industry by-Products and Their Application in Cosmetics-Case Study: Grape Pomace and Grapeseed

Grape pomace and grapeseed are agro-industrial by-products, whose inadequate treatment generates socioeconomic and environmental concerns. Nevertheless, it is possible to valorize them by extracting their bioactive compounds, such as antioxidants (phenolic compounds), vitamin E and fatty acids. The bioactive compounds were extracted using solid-liquid extraction. The yields for phenolic compounds were 18.4 ± 0.4% for grape pomace, and 17.4 ± 0.4%, for grapeseed. For the oil, the yields were 13.3 ± 0.2% and 14.5 ± 0.3% for grape pomace and grapeseed. Antioxidant capacity was assessed by the assay with 2,2-diphenyl-1-picrylhydrazyl (DPPH), and showed that phenolic extract has higher antioxidant capacity than the oils. Grape pomace and grapeseed extracts exhibit, correspondingly, values of 90.8 ± 0.8 and 87.5 ± 0.5 of DPPH inhibition and IC₅₀ of 48.9 ± 0.5 and 55.9 ± 0.7 μg_extract·mL_DPPH⁻¹. The antimicrobial capacity was assessed by the disk diffusion test, and revealed that, phenolic extracts inhibit the growth of Staphylococcus aureus and Staphylococcus epidermidis. The obtained extracts were incorporated in 10 face cream formulations, with slight modifications in quantities of formulation stabilizers. Their stability was studied for 35 days, and this revealed the possibility of incorporating extracts and oils obtained from by-products as antioxidants in cosmetics, and replacing synthetic ones. As a future recommendation, microencapsulation of the extracts should be performed, in order to increase their stability.

Evolution of the Olive Oil Industry along the Entire Production Chain and Related Waste Management

The production of olive oil involves the sustainable management of the waste produced along the entire production chain. This review examines the developments regarding cultivation techniques, production technologies, and waste management, highlighting the goals to be achieved and the most reasonable prospects. The results show that cultivation and production technology have evolved to an almost final solution to meet economic feasibility, keeping the oil’s high quality. Continuous horizontal decanters will coexist with traditional mills in many countries with old olive oil production and consumption traditions. High-quality products have conquered markets, especially in the wealthiest countries. At the same time, the exploitation of dried pomace by solvent extraction is increasingly an obsolete practice. However, waste management is still looking for one or a few reasonable solutions that meet modern society’s constraints. The enhancement of some experienced technologies and the full-scale application of emerging technologies and strategies should solve this problem in the short–medium term. A short discussion is reported on the possibility of unifying the nature and the quality of the waste, whatever the olive oil production method is. Furthermore, modern thermochemical treatment for solid wet organic waste disposal is examined and discussed.

Estimation of Sustainable Bioenergy Production from Olive Mill Solid Waste

The disposal of olive wastes and their wastewater is a major problem worldwide. An important recycling chain can be formed through biogas production and energy conversion from olive waste. This study developed an efficient and effective sustainable model for biogas production using anaerobic digestion conditions with the co-digestion of pretreated olive waste. The sample used was hard olive pomace, which was dried in an oven before being crushed to fine particles with a mortar and pestle. The sample was analyzed by a CE-440 Elemental Analyzer, and Fourier Transform Infrared Spectrophotometer (FTIR) analysis was performed using Shimadzu IRTracer-100. Through the analysis, a substantial amount of electrical energy of 769 kWh/t was found to be generated per ton of olive pomace due to the high volatile solid (VS) percentage of organic waste material incorporated during the calculation. Reduced land area for landfilling olive waste was calculated to be 108 m2 per year, whereas the potential to reduce landfill leachate production was evaluated to be 0.32 m3 per year.

Variation of soil microbial carbon use efficiency (CUE) and its Influence mechanism in the context of global environmental change: a review

Soil microbial carbon utilization efficiency (CUE) is the efficiency with which microorganisms convert absorbed carbon (C) into their own biomass C, also referred to as microorganism growth efficiency. Soil microbial CUE is a critical physiological and ecological parameter in the ecosystem’s C cycle, influencing the processes of C retention, turnover, soil mineralization, and greenhouse gas emission. Understanding the variation of soil microbial CUE and its influence mechanism in the context of global environmental change is critical for a better understanding of the ecosystem’s C cycle process and its response to global changes. In this review, the definition of CUE and its measurement methods are reviewed, and the research progress of soil microbial CUE variation and influencing factors is primarily reviewed and analyzed. Soil microbial CUE is usually expressed as the ratio of microbial growth and absorption, which is divided into methods based on the microbial growth rate, microbial biomass, substrate absorption rate, and substrate concentration change, and varies from 0.2 to 0.8. Thermodynamics, ecological environmental factors, substrate nutrient quality and availability, stoichiometric balance, and microbial community composition all influence this variation. In the future, soil microbial CUE research should focus on quantitative analysis of trace metabolic components, analysis of the regulation mechanism of biological-environmental interactions, and optimization of the carbon cycle model of microorganisms’ dynamic physiological response process.

Sorption of Ce(III) on magnetic/olive pomace nanocomposite: isotherm, kinetic and thermodynamic studies

Used for various high-tech applications, cerium is an important rare earth element (REE), and its sorption on various solids also is important considering purification and environmental and radioactive waste disposal. In view of the industrial and environmental terms, it is important to remove Ce³⁺ ions from an aqueous solution. Magnetite and magnetic olive pomace nanocomposite were thus fabricated by a partial reduction co-precipitation approach. The structure and morphological properties of the prepared nano-material and nanocomposite were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), vibrating sample magnetometry (VSM), and BET surface area analysis. The effects of parameters such as solution pH, contact time, initial Ce(III) concentration, and temperature on the sorption efficiency were studied. The maximum sorption capacities of the magnetite (MNP) and magnetic olive pomace nanocomposite (MOP) for Ce(III) ions were found to be 76.92 and 90.90 mgg^-1, respectively. The sorption data fitted well with Dubinin-Radushkevich isotherm model and the pseudo-second-order kinetic model. Thermodynamic parameters indicated that the sorption was non-spontaneous and endothermic. This paper reports the preparation of MNP and novel MOP and their application as efficient, sustainable adsorbents alternative to commercial ones for adsorption of cerium ions from aqueous solution.

Optimization of Pulsed Electric Field as Standalone "Green" Extraction Procedure for the Recovery of High Value-Added Compounds from Fresh Olive Leaves

Olive leaves (OLL) are reported as a source of valuable antioxidants and as an agricultural by-product/waste. Thus, a twofold objective with multi-level cost and environmental benefits arises for a "green" standalone extraction technology. This study evaluates the OLL waste valorization through maximizing OLL extracts polyphenol concentration utilizing an emerging "green" non-thermal technology, Pulsed Electric Field (PEF). It also provides further insight into the PEF assistance span for static solid-liquid extraction of OLL by choosing and fine-tuning important PEF parameters such as the extraction chamber geometry, electric field strength, pulse duration, pulse period (and frequency), and extraction duration. The produced extracts were evaluated via comparison amongst them and against extracts obtained without the application of PEF. The Folin-Ciocalteu method, high-performance liquid chromatography, and differential scanning calorimetry were used to determine the extraction efficiency. The optimal PEF contribution on the total polyphenols extractability (38% increase with a 117% increase for specific metabolites) was presented for rectangular extraction chamber, 25% v/v ethanol:water solvent, pulse duration (tpulse) 2 μs, electric field strength (E) 0.85 kV cm-1, 100 μs period (Τ), and 15 min extraction duration (textraction), ascertaining a significant dependence of PEF assisting extraction performance to the parameters chosen.

Effective Approach of Activated Jordanian Bentonite by Sodium Ions for Total Phenolic Compounds Removal from Olive Mill Wastewater

Olive mill wastewater (OMW) is nowadays considered a serious environmental problem, especially within the Mediterranean region. With this in mind, water shortages are also a very serious and prevalent concern in third world countries. The aim of this study is to investigate the feasibility of using Jordanian bentonite, a simple and natural clay, as a possible adsorbent to decrease the negative characteristics of raw OMW, as an approach to the development of a methodology that addresses the OMW problem without affecting freshwater resources. The purified bentonite was activated by sodium ions at room temperature. FTIR, XRD, TGA, and BET surface area measurements were performed. OMW was contacted with both purified and activated bentonite in the batch technique to figure out the optimum parameters for the adsorption process. Physiochemical parameters of OMW were measured before and after treatment. The maximum adsorption qm was found as 8.81 mg/g at 323 K for the total phenolic compounds. The Langmuir and Freundlich models were utilized to describe the equilibrium isotherms and both models fit well. The parameters of thermodynamic show that the adsorption process was feasible, spontaneous, and endothermic in nature. These promising results along with the sodium activation of bentonite significantly improve bentonite’s adsorption capacity.

Use of Pulsed Electric Field as a Low-Temperature and High-Performance “Green” Extraction Technique for the Recovery of High Added Value Compounds from Olive Leaves

Olive leaves (OLL), an agricultural waste by-product, are considered a significant bioresource of polyphenols, known as bioactive compounds. This study evaluates the pulsed electric field (PEF) technique for the extraction of polyphenols from OLL. The study parameters included a series of “green” solvents (ethanol, water as well as mixtures of them at a 25% step gradient) and different input values for the pulse duration of PEF. The phytochemical extraction degree was evaluated using total phenol concentration (Folin–Ciocalteu method) and high-performance liquid chromatography (HPLC) analyses, while the antioxidant activity was assessed using differential scanning calorimetry (DSC). The results obtained from the PEF extracts were compared with those of the extracts produced without the PEF application. The highest PEF effect was observed for aqueous ethanol, 25% v/v, using a pulse duration of 10 μs. The increase in the total polyphenols reached 31.85%, while the increase in the specific metabolites reached 265.67%. The recovery in polyphenols was found to depend on the solvent, the pulse duration of treatment and the structure of the metabolites extracted.

Olive Oil Dregs as a Novel Source of Natural Antioxidants: Extraction Optimization towards a Sustainable Process

Olive oil dregs (OOD), which are an underutilized by-product from oil mills, were used for the extraction of antioxidant compounds. The residues from three oil mills located in Campania (Southern Italy) were extracted with acidified methanol, and hydroxytyrosol (HT) was the main phenolic compound detected. Total phenolic content (TPC) and HT amount were measured. EVO Campania oil mill provided the residue with the highest TPC and HT quantities: 6.801 ± 0.159 mg Gallic Acid Equivalents (GAE)/g OOD and 519.865 ± 9.082 μg/g OOD, respectively. Eco-friendly extractions at different temperatures and times were performed on EVO Campania OOD, obtaining 9.122 ± 0.104 mg GAE/g OOD and 541.330 ± 64.087 μg/g OOD for TPC and HT, respectively, at 121 °C for 60 min. Radical Scavenging Activity (RSA), Superoxide Scavenging Activity (SSA), and Ferric Reducing Antioxidant Power (FRAP) were measured in OOD aqueous extracts. Extract prepared at 37 °C for 60 min showed the greatest RSA and SSA values (44.12 ± 1.82 and 75.72 ± 1.78, respectively), whereas extract prepared at 121 °C for 60 min exhibited the highest FRAP value (129.10 ± 10.49 μg Ascorbic Acid Equivalents (AAE)/mg). OOD extracts were able to protect sunflower oil from oxidation for 4 weeks at 65 °C. The overall results suggest that this novel residue can be usefully valorized by providing HT-rich extracts to use as antioxidant agents.

Bioactive Compounds in Waste By-Products from Olive Oil Production: Applications and Structural Characterization by Mass Spectrometry Techniques

In recent years, a remarkable increase in olive oil consumption has occurred worldwide, favoured by its organoleptic properties and the growing awareness of its health benefits. Currently, olive oil production represents an important economic income for Mediterranean countries, where roughly 98% of the world production is located. Both the cultivation of olive trees and the production of industrial and table olive oil generate huge amounts of solid wastes and dark liquid effluents, including olive leaves and pomace and olive oil mill wastewaters. Besides representing an economic problem for producers, these by-products also pose serious environmental concerns, thus their partial reuse, like that of all agronomical production residues, represents a goal to pursue. This aspect is particularly important since the cited by-products are rich in bioactive compounds, which, once extracted, may represent ingredients with remarkable added value for food, cosmetic and nutraceutical industries. Indeed, they contain considerable amounts of valuable organic acids, carbohydrates, proteins, fibers, and above all, phenolic compounds, that are variably distributed among the different wastes, depending on the employed production process of olive oils and table olives and agronomical practices. Yet, extraction and recovery of bioactive components from selected by-products constitute a critical issue for their rational valorization and detailed identification and quantification are mandatory. The most used analytical methods adopted to identify and quantify bioactive compounds in olive oil by-products are based on the coupling between gas- (GC) or liquid chromatography (LC) and mass spectrometry (MS), with MS being the most useful and successful detection tool for providing structural information. Without derivatization, LC-MS with electrospray (ESI) or atmospheric pressure chemical (APCI) ionization sources has become one of the most relevant and versatile instrumental platforms for identifying phenolic bioactive compounds. In this review, the major LC-MS accomplishments reported in the literature over the last two decades to investigate olive oil processing by-products, specifically olive leaves and pomace and olive oil mill wastewaters, are described, focusing on phenolics and related compounds.

Effect of Processing on Phenolic Composition of Olive Oil Products and Olive Mill By-Products and Possibilities for Enhancement of Sustainable Processes

The bio-functional properties of olive oil products and by-products rely greatly on the proportions and types of the endogenous phenolics that may favorably/unfavorably change during various processing conditions. The olive oil industrial activities typically produce (i) olive oils, the main/marketable products, and (ii) olive mill by-products. The mechanical processing of olive oil extraction is making progress in some areas. However, the challenges inherent in the existing system, taking into consideration, the susceptibilities of phenolics and their biosynthetic variations during processing, hamper efforts to ascertain an ideal approach. The proposed innovative means, such as inclusion of emerging technologies in extraction system, show potential for sustainable development of olive oil processing. Another crucial factor, together with the technological advancements of olive oil extraction, is the valorization of olive mill by-products that are presently underused while having great potential for extended/high-value applications. A sustainable re-utilization of these valuable by-products helps contribute to (i) food and nutrition security and (ii) economic and environmental sustainability. This review discusses typical processing factors responsible for the fate of endogenous phenolics in olive oil products/by-products and provides an overview of the possibilities for the sustainable processing to (i) produce phenolic-rich olive oil and (ii) optimally valorize the by-products.

Removal of Cadmium, Copper, and Lead From Water Using Bio-Sorbent From Treated Olive Mill Solid Residue

Olive Mill Solid Residue (OMSR) can be utilized as a bio-sorbent in wastewater treatment. Even though several studies on OMSR as a bio-sorbent were carried out, there is still a need to investigate a simple and relatively inexpensive OMSR treatment that increases pollutant removal. In this study; OMSR is used in batch experiments to remove toxic heavy metals from aqueous solutions including Cd²⁺, Cu²⁺, and Pb²⁺ ions. The effect of OMSR treatment (untreated; OMSR-U, treated with n-hexane; OMSR-H, and treated with water; OMSR-W) was investigated by chemical oxygen demand and cation exchange capacity. It was confirmed by both tests that OMSR-W was the best treatment. The same result was re-confirmed by batch uptake experiments of the heavy metal ions. Using OMSR-W as a bio-sorbent; the effect of several parameters such as pH, contact time, bio-sorbent concentration, metal ions concentration, and the presence of other metal species were studied to figure their influence on the metal ions uptake. The optimum conditions for single metal systems were found to occur at pH 5.5, an initial metal concentration of 50 mg/L, a shaking time of 60 minutes, a bio-sorbent concentration of 20 g/L. In binary metal ions solutions; Cd²⁺ uptake was increased in presence of Cu²⁺ or Pb²⁺. However, the uptake of Cu²⁺ and Pb²⁺ was decreased in presence of other metals. The equilibrium sorption data for single metal systems were described by the Langmuir isotherm model. The highest value of maximum uptake was found for Pb²⁺ (4.587 mg/g) followed by Cd²⁺ (4.525 mg/g) and Cu²⁺ (4.367 mg/g). These results show that OMSR-W, which has a very low economical value, could be used for the treatment of wastewater contaminated with heavy metals.

Olive Mill Wastes: A Source of Bioactive Molecules for Plant Growth and Protection against Pathogens

Simple Summary

Olive oil is the most common vegetable oil used for human nutrition, and its production represents a major economic sector in Mediterranean countries. The milling industry generates large amounts of liquid and solid residues, whose disposal is complicated and costly due to their polluting properties. However, olive mill waste (OMW) may also be seen as a source of valuable biomolecules including plant nutrients, anthocyanins, flavonoids, polysaccharides, and phenolic compounds. This review describes recent advances and multidisciplinary approaches in the identification and isolation of valuable natural OMW-derived bioactive molecules. Such natural compounds may be potentially used in numerous sustainable applications in agriculture such as fertilizers, biostimulants, and biopesticides in alternative to synthetic substances that have a negative impact on the environment and are harmful to human health.

Abstract

Olive oil production generates high amounts of liquid and solid wastes. For a long time, such complex matrices were considered only as an environmental issue, due to their polluting properties. On the other hand, olive mill wastes (OMWs) exert a positive effect on plant growth when applied to soil due to the high content of organic matter and mineral nutrients. Moreover, OMWs also exhibit antimicrobial activity and protective properties against plant pathogens possibly due to the presence of bioactive molecules including phenols and polysaccharides. This review covers the recent advances made in the identification, isolation, and characterization of OMW-derived bioactive molecules able to influence important plant processes such as plant growth and defend against pathogens. Such studies are relevant from different points of view. First, basic research in plant biology may benefit from the isolation and characterization of new biomolecules to be potentially applied in crop growth and protection against diseases. Moreover, the valorization of waste materials is necessary for the development of a circular economy, which is foreseen to drive the future development of a more sustainable agriculture.