Search Results (15)

This study investigates the diversity and provides a preliminary evaluation of the enzymatic potential of culturable fungi present in two-phase olive mill waste (TPOMW), a lignocellulose- and phenolic-rich agro-industrial by-product generated in large quantities in olive oil-producing countries. Ninety-four isolates, representing 31 species of the phyla Ascomycota, Basidiomycota, and Mucoromycota, were obtained and identified by using ITS, 28S, tef1-α, tub2, rpb2, act, and/or cal sequences. Among the identified taxa, two new Trichoderma species within the Harzianum clade, namely Trichoderma amurcicola (phylogenetically related to T. simile and T. guizhouense) and Trichoderma olivarum (phylogenetically related to T. simmonsii), were described following a multilocus phylogenetic analysis combined with a study of their morphoanatomical features. A rather high phylogenetic divergence was detected in Candida boidinii, Pleurostoma richardsiae, and Mucor circinelloides, while Cladosporium limoniforme, Mucor pseudolusitanicus, Stagonosporopsis ailanthicola, and Talaromyces nanjingensis were recorded for the first time in TPOMW. A preliminary screening revealed 29 species with cellulolytic and/or xylanolytic activities; 26 species displayed dye decolorization capacity, while ligninolytic and laccase activities were restricted to a few taxa. The most promising degraders of lignocellulosics included strains of Cladosporium limoniforme, C. ramotenellum, Fuscoporia ferrea, Peniophora lycii, and Pseudophlebia setulosa. Fungi detected in TPOMW are promising biotechnological tools to be exploited in the frame of circular economy applications. Full article

At present, taking into account the sustainability of the starting matrices, the biogas production industry is continuously growing, especially in consideration of ecological transition and circularity. The present study deals with the development of anaerobic bioreactors aimed at valorizing two specific wastes of the olive oil supply chain, i.e., the residual of protein hydrolysis process of three-phases olive pomace (OP-PH) and that recovered after the extraction of bioactive molecules from olive mill wastewater (OMWW waste). The energy consumed for biogas production varied from 0.52 kJ (OP and OMWW waste) to 0.97 kJ (OP-PH), while the energy produced for OP, OP-PH and OMMW waste was equal to 1.73, 2.94 and 1.60 kJ, respectively. The optimal production period was defined by considering only the range showing energy production higher than its consumption. According to this, OMWW showed the best performances, since it required 9 days (instead of 12 of untreated and treated OP) to reach the completion. The biogas production efficiency of the three-phase OP-PH waste calculated in the optimal production period, i.e., 12 days, was higher than the other samples, with a yield of 76.7% and a quantity of energy potentially producible corresponding to 1727.8 kJ/kg of volatile solids. These results pave the way for possible applications of this procedure for the planning of a multi-purpose biorefinery fed with by-products from the olive supply chain waste, thus promoting the use of sustainable waste materials from a circular economy perspective. Full article

The use of a two-phase decanter (TwPD) for olive-oil extraction produces wastes and byproducts (a small volume of water from oil washing, olive leaves from the defoliator, and a high moisture pomace which can be destoned) that contain valuable bioactive compounds, such as phenolics and/or triterpenic acids. So far, there is no (water) or limited information (leaves and the destoned pomace fraction) on their content of bioactives, especially triterpenic acids. To contribute to the characterization of such streams from cultivars of international interest, in the present study, samples obtained from five mills from the region of Laconia (from one or two harvests) in Greece, where Koroneiki cv dominates, were screened for phenols and/or triterpenic acids. The leaves and pomace were dried at two temperatures (70 °C and/or 140 °C), and the pomace was also destoned before analysis. The liquid wastes contained low amounts of total (TPC) phenols (<140 mg gallic acid/L), hydroxytyrosol (<44 mg/L), and tyrosol (<33 mg/L). The olive leaves varied widely in TPC (12.8–57.4 mg gallic acid/g dry leaf) and oleuropein (0.4–56.8 mg/g dry leaf) but contained an appreciable amount of triterpenic acids, mainly oleanolic acid (~12.5–31 mg/g dry leaf, respectively). A higher drying temperature (140 vs. 70 °C) affected rather positively the TPC/oleuropein content, whereas triterpenic acids were unaffected. The destoned pomace TPC was 15.5–22.0 mg gallic acid/g dw, hydroxytyrosol 3.9–5.6 mg/g dw, and maslinic 5.5–19.3 mg/g dw. Drying at 140 °C preserved better its bioactive phenols, whereas triterpenic acids were not influenced. The present findings indicate that TwPD streams may have a prospect as a source of bioactives for added-value applications. Material handling, including drying conditions, may be critical but only for phenols. Full article

In Spain and other Mediterranean countries, significant quantities of semi-solid olive mill waste are generated, which should be preferentially applied to agricultural soils to close nutrient cycles. However, two-phase olive mill waste (termed alperujo in Spanish) is known to pose risks to soil quality and plant production when applied to soil in large quantities. Alperujo has high contents of polyphenol substances, which can inhibit microbial growth and are also phytotoxic in nature. However, when applied in appropriate quantities and following specific methods, it is possible that the practice may not pose any risks, and this requires evaluation. As a waste management option, direct application of alperujo can supply plant nutrients and organic matter to degradation-prone Mediterranean soils. In order to validate this circular economy fertilization and soil protection strategy, an 18-month field experiment was undertaken, applying moderate quantities of alperujo on permanent crop groves throughout the Spanish region of Valencia. Eleven experimental parcels with permanent crops managed by farmers were identified to test two scenarios: a single application of 10 t/ha, and a second application of 10 t/ha after 10 months. Soil chemical parameters were assessed at 0, 6, 10, and 18 months. Soil organic carbon, total Kjeldahl nitrogen, pH, electrical conductivity, nitrates, and polyphenol contents were modified by alperujo application, but these effects were highly transient in nature, with generally no lasting effects after 4–6 months for either application scenario. Also, qualitative evaluations carried out by farmers revealed few effects, although some reductions in erosive processes and improvements in plant vigor were noted. As such, based on the measured parameters, it is concluded that the direct soil application of alperujo olive mill wastes at low application rates did not lead to any lasting detrimental effects on soil quality or compromise the productivity of permanent crops in this Mediterranean region. Full article

Owing to its important nutritional features, extra virgin olive oil (EVOO) is one of the world’s highest-value products, mostly manufactured in Mediterranean countries. However, its production exerts several negative environmental effects, mainly related to the agricultural phase (and the use of fertilizers, pesticides, etc.) and waste management. Olive oil can be extracted from the olive paste using different extraction systems, including pressure, centrifugation, and percolation. In particular, EVOO by-product composition strictly depends on the extraction technologies, and two- or three-phase centrifugal extraction methods are usually employed. Therefore, due to olive oil’s economic value, it might be useful to investigate its environmental impacts, to advise sustainable supply chain models. In this context, a valuable tool for assessing the product’s environmental compatibility is the Life Cycle Assessment, which is part of a broader Life Cycle Thinking philosophy. This research focused on evaluating the EVOO environmental impact by comparing two- and three-phases extraction processes. Additionally, two scenarios, (i.e., composting and bio-gasification), were proposed to assess the best valorisation strategy for the produced pomace. The results showed that the two-step extraction process was more sustainable than the three-step one in nine out of nine considered impact categories. By milling 1000 kg of olives, the first technology approximately produces 212 kg CO₂ eq, the latter 396 kg CO₂ eq. Finally, pomace valorisation by bio-gasification was found as the best recovery process, able to confer greater environmental benefit than composting. Full article

Over the last decade, the two-phase centrifugation system for olive-oil extraction has become dominant in Slovenia. There are many suggestions for the exploitation of two-phase OMW, but among the suggested methods, direct spreading on agricultural land appears to be operationally simple and economically feasible for Slovenia. As there is little information available about two-phase OMW produced in the northern Mediterranean regions, the aim was to determine its composition and evaluate its use as a soil amendment in olive groves. This study shows that the characteristics of two-phase olive-mill waste produced in northern Mediterranean regions are similar to those of other countries. In addition, the calcareous characteristics of the Mediterranean soil can reduce its phytotoxic effects and might thus represent a natural system for olive-mill waste treatment. Phenolic compounds in the two-phase olive-mill waste are rapidly decomposed, and the soil has a high buffering capacity. Furthermore, the results of the soil analysis also showed some effects on the soil properties, such as a significant increase in K₂O and soil organic carbon. The combined application of two-phase olive-mill waste and mineral fertilizer to olive groves on eutric cambisols has positive effects on the physical, chemical and biochemical properties of the soil. Full article

The olive oil industry produces high amounts of waste, which need to be valorized in a more sustainable way as an alternative to its traditional use as an energy source, with high associated CO₂ emissions. Rice (Oryza sativa L.) is one of the most important crops for global food security; however, the traditional cropping systems under flooding lead to an important decrease of soil quality, as well as relevant emissions of greenhouse gases (GHG). The aim of this study was to assess the GHG emission from rice fields amended with composted two-phase olive mill waste (C-TPOW), in Mediterranean conditions. A field experiment was carried in rice cultivated by the traditional system, either unamended (Control) or amended with C-TPOW (Compost). GHG emissions were measured over three years following a single C-TPOW application (80 Mg ha⁻¹ only in the first year of study), so that the results found in the first and third years correspond to its direct and residual effects, respectively. Compost decreased CO₂ emissions relative to Control by 13% and 20% in the first and third year after C-TPOW application, respectively. However, in the case of CH₄ and N₂O, increases in the total cumulative emission were recorded in Compost relative to Control throughout the study, in agreement with the highest β-glucosidase and urease activity observed in the amended soil. The values of global warming potential (GWP) and yield-scaled GWP increased by 14% and 11%, respectively, in Compost relative to Control in the first year, but no significant differences between treatments were observed three years after application for GWP and yield-scaled GWP. Therefore, the use of C-TPOW as soil amendment in rice fields could be a good option since its impact on GHG emissions seems to decrease over time, while the benefit for soil remained clear even after 3 years. Full article

Olive mill wastes represent an important environmental problem. Their high phenol, lipid, and organic acid concentrations turn them into phytotoxic materials. Specifically, wet olive pomace (WOP) is the waste generated in the two-phase continuous extraction process. WOP is a paste with around 60% water. The total volume of WOP generated is around 0.25 L/kg of olives processed. Its current waste management practices result in environmental problems as soil contamination, underground seepage, water-bodies pollution, and foul odor emissions. Some valorization alternatives include composting, biological treatments, direct combustion for energy production, or direct land application. The leather industry is making great efforts to apply cleaner processes while substituting chemical products for natural products. In this way, different alternatives are being studied, such as the use of zeolites, triazine derivatives, grape seed extract, olive leaf extract, etc. In this work, the use of wet olive pomace is presented as a possible alternative to conventional vegetable tannins (mimosa, quebracho, chestnut, etc.). Although different projects and studies have been developed for the valorization of olive mill wastes, there is completely a new approach to the WOP application for tanning purposes. This study shows that WOP has a significant number of polyphenolic substances, so it has a great potential to be used as a tanning agent. Specifically, this study has been able to determine that, of the polyphenols present in WOP, 39.6% correspond to tannins that are capable of tanning the skin. Additionally, it contains 14.3% non-tannins, that is, molecules that by themselves do not have the capacity to tan the leather but promote the tanning mechanism and improve the properties of the tanned leather. Full article

In this study, the combustion of olive byproducts was investigated using the TG-FTIR technique. Different types of olive biomass were considered: twigs, leaves, olive-mill waste from the two-phase decanting method, and wastewater from the three-phase system. The reaction regions, ignition, and burnout temperatures at different heating rates were determined using TG/DTG analysis and the thermogravimetry results. Comprehensive combustion, ignition, burnout, and flammability indexes were also calculated. The highest combustion index values were obtained for waste from the three-phase system, followed by the two-phase decanting method, then with leaves and small twigs. The order of the index values indicated that the sample from the three-phase process ignited more quickly and yielded faster. The changes in activation energy calculated using different model-free isoconversional methods—Friedman, Ozawa–Flynn–Wall, and Kissinger–Akahira–Sunose—fell within the range of 130–140 kJ/kmol. FTIR analyses presented differences in the exhaust gas composition for specific combustion temperature ranges. Full article

Diverse vegetable oils are extracted from oleagenic trees and plants all over the world. In particular, olive oil represents a strategic socio-economic branch in the Mediterranean countries. These countries use either two or three-phase olive oil extraction systems. In this work, we focus on the by-products from three-phase olive oil extraction, which are the liquid olive mill wastewater (OMW) and the solid olive mill pomace (OMP) rejected in evaporative ponds. The disposal of this recalcitrant waste poses environmental problems such as the death of different species of insects and animals. In-depth ICP-OES analysis of the heavy metal composition of OMW and OMP revealed the presence of many metals ranging from non-toxic to highly toxic. The LC-HRMS characterization of these by-products indicated the presence of several secondary metabolites harmful to humans or to the environment. Thus, we aimed to identify OMW and OMP indigenous microbiota through metagenomics. The bacterial population was dominated by the Acetobacter (49.7%), Gluconobacter (17.3%), Gortzia (13.7%) and Nardonalla (5.3%) genera. The most abundant fungal genera were Nakazawaea, Saccharomyces, Lachancea and Candida. These microbial genera are responsible for OMW, OMP and soil toxicity alleviation. Full article

The olive oil production is an important industrial sector in many Mediterranean areas, but it is currently struggled by the necessity of a proper valorisation of the olive mill solid waste or alperujo. The alperujo is the main by-product generated during the two-phase olive oil extraction, accounting for up to 80% of the initial olive mass. The alperujo is a source of valuable compounds, such as the pomace olive oil or highly interesting phenolic compounds. In the present research, a novel biorefinery approach has been used for phenolic compounds recovery. However, the extraction of these valuables compounds generates different exhausted phases with high organic matter content that are required to be managed. This study consists of the evaluation of the anaerobic biodegradability of the different fractions obtained in a novel biorefinery approach for the integral valorisation of alperujo. The results show that the different phases obtained during the biorefinery of the alperujo can be effectively subjected to anaerobic digestion and no inhibition processes were detected. The highest methane yield coefficients were obtained for the phases obtained after a two-months storages, i.e., suspended solids and liquid phase free of suspended solids, which generated 366 ± 7 mL CH₄/g VS and 358 ± 6 mL CH₄/g VS, respectively. The phenol extraction process reduced the methane yield coefficient around 25% due to the retention of biodegradable compounds during the extraction process. Regardless of this drop, the anaerobic digestion is a suitable technology for the stabilization of the different generated residual phases, whereas the high market price of the extracted phenols can largely compensate the slight decrease in the methane generation. Full article

Olive oil byproducts show differences according to the olive oil extraction systems, which are called olive mill solid wastes, olive oil wastewater and olive oil wastewater sludge. Three different kinds of composts, including two-phase and three-phase olive mill solid wastes, and olive oil wastewater sludge were produced with separated dairy manure, poultry manure, and straw. The composts obtained from two-phase and three-phase olive mill solid wastes and olive oil wastewater sludge were named as two-phase, three-phase, and water sludge composts, respectively. They were separately enriched by rock phosphate and potassium salt. These composts were mixed with peat in a ratio of 0%, 25%, 50%, 75%, and 100% (v/v). Tomato seeds were sown in all mixtures on 3 February 2016. All the seeds were sown into 2 trays and each plug included 2 replicates. The trays were left in a germination room for 3 days, then moved to a heated greenhouse which is specialized for growing seedlings, and the seedlings were grown there for 3 weeks. The results showed that increasing compost ratios in the growing medium and also the enrichment of the growing medium increased organic matter content, electrical conductivity, and macro and micro nutrient concentrations. The germination period lasted longer with increasing compost ratios. The shoot length was lower at a compost ratio of over 50% excluding water sludge compost, which reacted to over 75%. The highest plant dry weights were obtained in the plants grown on the media with compost ratios of 50%, 25%, and 25% for water sludge compost, enriched two-phase compost, and enriched three-phase compost, respectively. We concluded that the composts obtained from two-phase and three-phase olive mill solid wastes and olive oil waste water sludge can be used without any need of enrichment and a ratio of 25% was found appropriate in most of the measured properties. Full article

Verticillium Wilt of Olive, a disease caused by the hemibiotrophic vascular fungus Verticillium dahliae Kleb. presents one of the most important constraints to olive production in the world, with an especially notable impact in Mediterranean agriculture. This study evaluates the use of RGB vegetation indexes in assessing the effects of this disease during the biotrophic phase of host-pathogen interaction, in which symptoms of wilt are not yet evident. While no differences were detected by measuring stomatal conductance and chlorophyll fluorescence, results obtained from RGB indexes showed significant differences between control and inoculated plants for indexes Saturation, a*, b*, green Area (GA), normalized green-red difference index (NGRDI) and triangular greenness index (TGI), presenting a reduction in plant growth as well as in green and yellow color components as an effect of inoculation. These results were contrasted across two scenarios of mineral fertilization in soil and soil amended with two different olive mill waste composts, presenting a clear interaction between the host-pathogen relationship and plant nutrition and suggesting the effect of V. dahliae infection during the biotrophic phase was not related to plant water status. Full article

The semi-solid wastes (pomace or alperujo) produced in the two-phase olive oil extraction process contains extremely high organic load and phenolic substances. Efficient treatment of such kinds of wastes using membrane filtration, should be sought to reduce the hazardous effects to the environment. On the other hand, phenolic compounds can be isolated and purified up to a level of commercial exploitation using the membrane technology. Firstly, the extraction process with mixtures of water and ethanol was optimized by testing extraction parameters (e.g., solvent’s mixture, duration, and temperature) at laboratory scale. Next, extraction was conducted using larger volumes and the treatment was continued in a pilot membrane filtration system, consisted of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes. The extracted solution from the olive oil pomace was fed to the pilot membrane filtration system, where all fat, lipids, and solids were removed while the phenolic compounds were concentrated in the retentate streams of NF and/or RO. Total phenolic content (TPC) at the RO’s concentrate stream was 225 mg/L and at the final effluent was lower than 10 mg/lt. The chemical oxygen demand (COD) value at the final effluent was much lower (~280 mg/L) than in the feed stream (>32,000 mg/L). Full article

Alperujo—a two-phase olive mill waste that is composed of olive vegetation water and solid skin, pulp, and seed fragments - is a highly valuable olive by-product due to its high content in phenolic compounds. In this study, we assessed whether β-cyclodextrin (β-CD), which is used to extract and protect alpejuro phenolic compounds (hydroxytyrosol-O-glucoside, tyrosol, caffeic, and p-coumaric acids) could impact on their bioaccessibility (i.e., the percentage of molecule found in the aqueous phase of the digesta) and uptake by intestinal cells, by using an in vitro digestion model and Caco-2 TC7 cells in culture, respectively. Our results showed that β-CD did not change the bioaccessibility of the selected phenols. Hydroxytyrosol-O-glucoside and caffeic did not cross Caco-2 cell monolayers. Conversely ferulic acid, identified as the main caffeic acid intestinal metabolite, was absorbed through intestinal cell monolayers (~20%). Interestingly, β-CD moderately but significantly improved the local absorption of tyrosol and p-coumaric acid (2.3 + 1.4% and 8.5 ± 4.2%, respectively, p < 0.05), even if their final bioavailability (expressed as bioaccessibility × absorption by Caco-2 cells) was not modified (16.2 ± 0.6% vs. 16.8 ± 0.5% for tyrosol and 32.0 ± 3.2% vs. 37.2 ± 3.2% for p-coumaric acid, from pure alperujo and alperujo complexed with β-CD, respectively). Overall, our results show that β-CD is an interesting extraction and storage agent for phenolic compounds that does not alter their in vitro bioavailability. Full article