Assessment and valorization of treated and non-treated olive mill wastewater (OMW) in the dry region

PurposeThe quantity of Olive by-products does not stop increasing and a water shortage that threatens the olive tree culture; require a serious valuation of these by-products. A comparative and valorization study of two kinds of OMW; Fresh OMW (FOMW), directly issue from three-phase continuous extraction factory and Disposal Evaporation Ponds OMW (DOMW) were done.MethodsPhysico-chemical and biological parameters of OMWs and soil irrigated with OMWs, respectively, were determined. An antibacterial activity test of FOMW against Clinic Standard Bacteria was determined. A statistical analysis was performed for all defined parameters.ResultsA significant increase of pH value of 6 and a lower failure of the EC in 8.94 (mS/cm−1) were registered after OMW disposal in evaporation ponds. We registered a fall of BOD5 and COD from 61.05–116.37 (g/L) to 55.67–103.82 (g/L), respectively. A significant increment of phenol compound removal was observed after OMW disposal. However, a switch of fatty acids distribution and content was observed, which several fermentation pathways could explain took place. This result suggested by a clear shift in biomass composition. An important soil fertility after DOMW soil irrigated was traduced by an important value of the germination index (170.55%) and efficient organic matter increment of 2.3%. A CMI rate of 32.76 (μg mL−1) was determined by FOMW against different clinic standard bacteria.ConclusionA spectacular soil fertility effect was obtained from DOMW soil spreading, that efficiently evaluate the OMW biological treatment. In addition, the FOMW was valorized as its powerful antibacterial.

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title: Review: Effects of olive mill wastewater application on soil properties and plants growth
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title: Olive mill wastewater microconstituents composition according to olive variety and extraction process.
abstract: Olive oil production yields a considerable amount of wastewater, a powerful pollutant that is currently discarded but could be considered as a potential source of valuable natural products due to its content in phenolic compounds and other natural antioxidants. The aim of this work was to explore the variability in olive mill wastewater composition from Algerian olive oil mills considering extraction processes (traditional discontinuous press vs 3-phases centrifugal system) and olive varieties (Azerraj, Sigoise, Chemlal). Whereas pH, dry or organic matter content didn't vary, there was a significant difference in ash content according to extraction process and olive variety. Carotenoid content was 2.2-fold higher with 3-phases than with press systems whereas tocopherol content was not significantly different. Among the phenolic compounds quantified, tyrosol was usually the most abundant whereas oleuropein concentrations were highly variable. Differences in phenolic compound concentrations were more pronounced between olive varieties than between processes.

title: Olive mill wastes: Biochemical characterizations and valorization strategies
abstract: The olive mill waste generated from olive oil extraction is a major environmental issue, particularly in Mediterranean areas. The extraction of olive oil is achieved through discontinuous or continuous processes. The two processes yield three fractions: a solid residue and two liquid phases (oil and olive mill wastewater). The characterization of these two by-products showed that they are mainly composed of phenolic compounds, carbohydrates, organic acids and mineral nutrients variably distributed depending on the process employed and the agronomic practices. Untreated olive by-products discharged between November and March into the environment are a major ecological issue for olive oil-producing countries due to their high toxic organic loads, low pH, and high chemical and biological demands. In this context, recent research studies highlight on the treatment approaches and valorization options for dealing with olive mill waste residues, predominantly those allowing for the recovery of valuable natural components such as phenolic compounds, dietary fibers, animal feed, biofuel, biogaz, enzymes, polymers and other. The impact of the chemical heterogeneity and water content of olive mill by-products about these processes of valorization and bioconversion is discussed.

title: Technologies for olive mill wastewater (OMW) treatment: a review
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title: Treatment and valorization of olive mill wastewaters
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title: Identification and characterisation of phenolic compounds extracted from Moroccan olive mill wastewater
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title: Phenolic profiles of olive mill wastewaters treated by membrane filtration systems
abstract: Olive mill wastewater is an important by-product obtained after olive oil extraction. In this investigation, the phenolic composition of olive mill wastewater treated with a semi-industrial membrane filtration system, including ultrafiltration and reverse osmosis modules, was studied. In particular, untreated olive mill wastewater was compared with the permeate and the concentrate fractions of each filtration step. 
 
 
 
RESULTS 
 
3,4-(dihydroxyphenyl) ethanol and p-(hydroxyphenyl) ethanol were the main compounds of all olive mill wastewater analyzed. A total of 32 compounds, detected at 240 or 280 nm by HPLC-DAD, were considered for phenol quantification. Ultrafiltration reduced phenol concentration by about 40% with respect to the initial level; in the permeate of reverse osmosis, the phenol concentration ranged from 0 to 1% of the initial content. In contrast, the content of phenolic compounds was increased about 2.6 fold in reverse osmosis concentrate. 
 
 
 
The membranes used in this investigation produced a high phenol content fraction than might be used as functional component in food, cosmetic or feed products. Moreover, the final wastewater obtained by reverse osmosis, thanks to the low content of phenols, could be recycled and reused in the oil mill, reducing water consumption and disposal costs.

title: A Short Review of Techniques for Phenol Removal from Wastewater
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title: Effects of spreading olive mill wastewater on soil properties and crops, a review
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title: Olive-mill wastewater spreading in Southern Tunisia : effects on a barley crop ( Hordeum Vulgare L . )
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title: Effects of olive mill wastewater spreading on the physico-chemical and microbiological characteristics of soil
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title: The Olive Mills Waste Water (OMW) as an Organic Amendment for Controlling Wind Erosion in Southern Tunisia by Improving the Soil Surface Structure
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title: A CRITICAL EXAMINATION OF A RAPID METHOD FOR DETERMINING ORGANIC CARBON IN SOILS—EFFECT OF VARIATIONS IN DIGESTION CONDITIONS AND OF INORGANIC SOIL CONSTITUENTS
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title: Comparative antibacterial and antifungal effects of some phenolic compounds.
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title: Physicochemical Characterization of Olive Oil Mill Wastewaters in the eastern region of Morocco
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title: Catabolism of aromatic acids in Trichosporon cutaneum
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title: Phenolic removal in olive oil mill wastewater by strains of Pleurotus spp. in respect to their phenol oxidase (laccase) activity.
abstract: The ability of several Pleurotus spp. strains to remove phenolic compounds from an olive oil mill wastewater (OMW) was studied. All strains tested in this work were able to grow in OMW without any addition of nutrients and any pre-treatment, except sterilization. High laccase activity was measured in the growth medium, while 69-76% of the initial phenolic compounds were removed. The black color of OMW became yellow-brown and brighter as the strains grew. The lowest phenolic concentrations were reached after 12/15 days. A decrease of the phytotoxicity, as described by the parameter Germination Index, was noticed in the OMW treated with some Pleurotus spp strains, although this decrease was not proportional to the phenolic removal. A new parameter, namely Phenol-toxicity Index, was considered in the present paper. Using this parameter it was found that the remaining phenolics and/or some of the oxidation products of the laccase reaction in the treated OMW were more toxic than the original phenolic compounds.

title: Evaluation of olive oil mill wastewaters acute toxicity: a study on the mitochondrial bioenergetics.
abstract: Acute toxicity of olive mill wastewaters (OMW), collected from a continuous olive mill, was evaluated in rat liver mitochondrial bioenergetics. Inhibition of respiratory activities in state 4, state 3, and uncoupled respiration are essentially mediated through partial inhibitions of mitochondrial complexes II and III. ATPase activity was considerably less depressed by OMW than ATP synthase activity (a difference of 42%). The inhibition observed on ATP synthase is mostly the result of an inhibition on the redox complexes. Ultimately, the OMW-induced loss of phosphorylation capacity was not only the result of a direct effect of OMW on the enzymatic complex (F(0)-F(1) ATPase), but also the result of a deleterious effect on the integrity of the mitochondrial membrane, which can promote an inhibition of the respiratory complexes and an increase of the proton permeability of the inner membrane.

title: In brain mitochondria the branched-chain fatty acid phytanic acid impairs energy transduction and sensitizes for permeability transition.
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title: Vacuum promotes metabolic shifts and increases biogenic hydrogen production in dark fermentation systems
abstract: The successful operation of any type of hydrogen-producing bioreactor depends on the performance of the microorganisms present in the system. Both substrate and partial gas pressures are crucial factors affecting dark fermentation metabolic pathways. The main objective of this study was to evaluate the impact of both factors on hydrogen production using anaerobic granular sludge as inoculum and, secondly, to study the metabolic shifts of an anaerobic community subjected to low partial gas pressures. With this goal in mind, seven different wastewater (four synthetic media, two industrial wastewater, and one domestic effluent) and the effect of applying vacuum on the systems were analyzed. The application of vacuum promoted an increase in the diversity of hydrogenproducing bacteria, such as Clostridium, and promoted the dominance of acetoclastic- over hydrogenotrophic methanogens. The application of different media promoted a wide variety of metabolic pathways. Nevertheless, reduction of the hydrogen partial pressure by application of vacuum lead to further oxidation of reaction intermediates irrespective of the medium used, which resulted in higher hydrogen and methane production, and improved the COD removal. Interestingly, vacuum greatly promoted biogenic hydrogen production from a real wastewater, which opens possibilities for future application of dark fermentation systems to enhance biohydrogen yields.

title: Biochemistry of peroxisomes in health and disease
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title: Detection and quantification of long chain fatty acids in liquid and solid samples and its relevance to understand anaerobic digestion of lipids.
abstract: A method for long chain fatty acids (LCFA) extraction, identification and further quantification by gas chromatography was developed and its application to liquid and solid samples collected from anaerobic digesters was demonstrated. After validation, the usefulness of this method was demonstrated in a cow manure digester receiving pulses of an industrial effluent containing high lipid content. From the LCFA analysis data it was showed that the conversion of oleic acid, the main LCFA fed to the reactor, by the adapted biomass became faster and more effective along the successive pulses. Conversely, the accumulation of palmitic acid in the solid phase suggests that degradation of this LCFA, under these conditions, is less effective.

title: Strategies for recovering inhibition caused by long chain fatty acids on anaerobic thermophilic biogas reactors.
abstract: Long chain fatty acids (LCFA) concentrations over 1.0 gL(-1) were inhibiting manure thermophilic digestion, in batch and semi-continuous experiments, resulting in a temporary cease of the biogas production. The aim of the work was to test and evaluate several recovery actions, such as reactor feeding patterns, dilution and addition of adsorbents, in order to determine the most appropriate strategy for fast recovery of the reactor activity in manure based plants inhibited by LCFA. Dilution with active inoculum for increasing the biomass/LCFA ratio, or addition of adsorbents for adsorbing the LCFA and reducing the bioavailable LCFA concentration, were found to be the best recovery strategies, improving the recovery time from 10 to 2 days, in semi-continuously fed systems. Moreover, acclimatization was introduced by repeated inhibition and process recovery. The subsequent exposure of the anaerobic biomass to an inhibitory concentration of LCFA improved the recovery ability of the system, indicated as increasing degradation rates from 0.04 to 0.16 g COD_CH(4)/g VS day. The incubation time between subsequent pulses, or discontinuous LCFA pulses, seems to be a decisive process parameter to tackle LCFA inhibition in manure anaerobic co-digestion.

title: Recovery of oleate‐inhibited anaerobic digestion by addition of simple substrates
abstract: Four laboratory-scale anaerobic digesters were deliberately and completely inhibited by feeding sodium oleate to such an extent that no methane was produced from the digesters. Three of them were then respectively fed glucose, cysteine or glucose and cysteine along with sodium oleate, while the remaining digester was operated as control reactor and continued to be fed with only sodium oleate. Oligonucleotide probes ARC915, EUB338, MB310, MC1109, MSMX860 and MG1200 were used to target and quantify specific groups of microbes, Archaea, Bacteria, Methanobacteriales, Methanococcales, Methanosarcinaceae, and Methanomicrobiaceae, Methanocorpusculaceae and Methanoplanaceae respectively throughout the operation of reactors. Addition of glucose and/or cysteine assisted with the recovery of methane production from oleate inhibition. The addition of glucose was more effective than cysteine, while the combination of glucose and cysteine was most effective on this recovery. The addition of these substrates also stimulated the degradation of oleate in the reactor. Daily methane production from the digesters correlated negatively with residual oleate concentration and positively with Archaea counts. Addition of glucose was more effective than cysteine on increasing the number of Archaea cells, while cysteine was more effective in increasing the number of Bacteria cells. All microbial populations recovered to pre-inhibition levels within 40 days when glucose together with cysteine was fed.

title: Enhancement of the anaerobic digestion of olive mill wastewater by the removal of phenolic inhibitors
abstract: Olive mill wasterwater (OMW) has a high organic pollutant load (45–130 g COD/litre) including various phenolic compounds, of which caffeic acid, thyrosol and hydroxythyrosol occur in the highest proportions. These two features make it impossible to purify OMW anaerobically unless a prior dilution is effected. Partial removal of some of the organic matter and phenolic compounds, by aerobic pretreatment with Geotrichum candidum is described. This provides a partially purified effluent that, for the same COD level as that of the original OMW, is degraded anaerobically more rapidly than original OMW as a result of the increase in methanogenic activity by 39 ml CH4 STP /g VSS day for a COD of 7 g /litre. Finally, the presence of a sepiolite support (Pansil) in the digestors is shown to increase the biodegradability of the OMWs and the yield coefficient of the product (Yp).

title: Synergistic Antibacterial Effects of Polyphenolic Compounds from Olive Mill Wastewater
abstract: Polyphenols or phenolic compounds are groups of secondary metabolites widely distributed in plants and found in olive mill wastewater (OMW). Phenolic compounds as well as OMW extracts were evaluated in vitro for their antimicrobial activity against Gram-positive (Streptococcus pyogenes and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae). Most of the tested phenols were not effective against the four bacterial strains when tested as single compounds at concentrations of up to 1000 μg mL−1. Hydroxytyrosol at 400 μg mL−1 caused complete growth inhibition of the four strains. Gallic acid was effective at 200, and 400 μg mL−1 against S. aureus, and S. pyogenes, respectively, but not against the gram negative bacteria. An OMW fraction called AntiSolvent was obtained after the addition of ethanol to the crude OMW. HPLC analysis of AntiSolvent fraction revealed that this fraction contains mainly hydroxytyrosol (10.3%), verbascoside (7.4%), and tyrosol (2.6%). The combinations of AntiSolvent/gallic acid were tested using the low minimal inhibitory concentrations which revealed that 50/100–100/100 μg mL−1 caused complete growth inhibition of the four strains. These results suggest that OMW specific fractions augmented with natural phenolic ingredients may be utilized as a source of bioactive compounds to control pathogenic bacteria.

title: Bioscreening of Australian olive mill waste extracts: biophenol content, antioxidant, antimicrobial and molluscicidal activities.
abstract: The biophenolic fraction was characterized in olive mill waste (OMW) obtained as a by-product from processing of Mission and Frantoio olive fruit. OMW produced from the Mission fruit contained higher total phenol content. Individual biophenols with the exception of verbascoside and a hydroxytyrosol-secoiridoid were also present at higher concentrations in the OMW produced from Mission cultivar. Antioxidant activities were measured in aqueous (DPPH) and emulsion (BCBT) systems. The Frantoio extract was more active than the Mission extract in the DPPH assay - EC(50) values were 28.3+/-1.7 ppm and 34.7+/-1.7 ppm, respectively. Activities were reversed in the BCBT, with the Mission extract (EC(50) 60.6+/-2.3 ppm) more potent than the Frantoio extract (EC(50) 79.9+/-2.0 ppm), and this may be related to the more lipophilic nature of the Mission extract. Both extracts showed broad spectrum antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa; whereas individual biophenols (hydroxytyrosol, luteolin, oleuropein) showed more limited activity. Molluscicidal activity was measured against Isidorella newcombi and LD(50) values were 424 ppm and 541 ppm for Mission and Frantoio extracts, respectively. The results suggest that OMW may be utilised as a source of bioactive compounds.

title: Extraction of antioxidants from olive mill wastewater and electro-coagulation of exhausted fraction to reduce its toxicity on anaerobic digestion.
abstract: Liquid-liquid extraction was used in order to recover phenolic compounds from centrifuged olive mill wastewater (OMW), a polluting by-product of olive oil production process, and to reduce their toxicity for a subsequent aerobic or anaerobic digestion. Phenolic compounds were identified in untreated and treated OMW by gas chromatography coupled to mass spectrometry (GC-MS). The experimental results of ethyl acetate extraction showed that the monomers recovery efficiency was over 90%. This pre-treatment resulted in the removal of the major LMM phenolic compounds and a small part of HMM polyphenols. The aerobic treatment of the exhausted OMW fraction removed 78.7% of the soluble COD. In the case of anaerobic digestion at OLR ranged from 1 to 3.5 gCOD l(-1)day(-1), methanisation process exhibited high methane yield as 0.3 l CH4 produced per g COD introduced and high COD removal (80%). However, a disruption of the process was observed when the OLR was increased to 4.5 gCODl(-1)day(-1). A pre-treatment by electro-coagulation resulted in decreasing the toxicity and enhancing the performance of methanisation operated at higher OLR from 4 to 7.5 gCODl(-1)day(-1).

title: The impact of olive mill wastewater application on flow and transport properties in soils
abstract: Olive mill wastewater (OMW) is the main waste product of the olive oil industry and is characterized by a high salinity and high organic matter content. Until today, in several olive oil producing countries untreated OMW is pumped onto agricultural land with possible adverse effects on soil properties. The main objective of this study was to investigate the long-term effects of OMW application on soil hydrophobicity, hydraulic conductivity and infiltration rate. In addition, the generation of transport patterns was studied using dye tracer tests. The results showed that the regular application of OMW for 5 and 15 years increased soil hydrophobicity and decreased the drainable porosity (Φ < 30 μm), as a consequence of a rising organic matter content. OMW application furthermore reduced the soil hydraulic conductivity compared with a control site. Likewise, the infiltration rate decreased in the 5 years treatment compared with the control. The highest infiltration rate, however, was observed for the 15 years treatment because of the presence of large and deep shrinkage cracks that do not completely close upon rewetting. The dye infiltration depth in the control was small and homogeneous compared to the plots with OMW application, which fostered the generation of heterogeneous flux fields including preferential flow conditions. As a consequence, fields irrigated with OMW are more prone to groundwater contamination with substances either originating from the OMW itself or from agricultural chemicals.

title: Environmental effects caused by olive mill wastewaters: toxicity comparison of low-molecular-weight phenol components.
abstract: Olive oil mill wastewaters (OMWs) show significant polluting properties due to their content of organic substances, and because of their high toxicity toward several biological systems. Wastewaters' toxicity has been attributed to their phenolic constituents. A chemical study of wastewaters from a Ligurian oil mill characterized phenolic products such as 1,2-dihydroxybenzene (catechol), derivatives of benzoic acid, phenylacetic acid, phenylethanol, and cinnamic acid. The OMWs were fractioned by ultrafiltration and reverse osmosis techniques and tested for toxicity on aquatic organisms from different trophic levels: the alga Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum); the rotifer Brachionus calyciflorus; and two crustaceans, the cladoceran Daphnia magna and the anostracan Thamnocephalus platyurus. The fraction most toxic to the test organisms was that from reverse osmosis containing compounds of low molecular weight (<350 Da), and this was especially due to the presence of catechol and hydroxytyrosol, the most abundant components of the fraction.

title: Model study on the effect of 15 phenolic olive mill wastewater constituents on seed germination and Vibrio fischeri metabolism.
abstract: Olive mill wastewaters (OMW) can be a severe problem when disposed of as untreated because of their high organic load, elevated concentration of polyphenols, and moderately low biodegradability. In the present study, the acute toxicity of 15 compounds with low molecular weight (<350 Da), catechol, four benzoic acids, three phenylacetic acids, three phenylethanols, and four cinnamic acids, already isolated from the reverse osmosis in the fractionation of OMW, was assessed on the marine bacterium Vibrio fischeri and on the seeds of two dicotyledonous species Cucumis sativus and Lepidium sativum, and on one monocotyledon Sorghum bicolor. Results of phytotoxicity showed that the most toxic compounds were catechol (EC50s ranging from 0.40 mmol/L for S. bicolor to 1.09 for C. sativus) and hydroxytyrosol, (EC50s ranging from 0.47 mmol/L for S. bicolor to 1.55 for C. sativus) while the toxic potential on bacteria was particularly elevated with EC50 values 1 or 2 orders less than phytotoxicity. These results suggested that the risk of OMW disposal may be more elevated for the water compartment than for the soil.

title: Olive-mill wastewater spreading in southern Italy: effects on a durum wheat crop
abstract: The results of an experiment on olive-mill wastewater (OMWW) distribution in durum wheat are reported. The OMWW was spread without pre-treatments, at the maximum amount allowed by law, on a durum wheat crop in a Mediterranean environment. The experiment was carried out on the same plots from 1999 to 2001 in Monopoli (southern Italy) with two treatments—(not treated) NT and (treated) T. In the treated plots, OMWW obtained from a traditional press system was spread, during the crop vegetative phase, at 50 m 3 ha � 1 . Soil and OMWW were characterised from both physical and chemical aspects. An automatic meteorological station recorded main climatic variables during the period from January to May each year. During the growth cycle of durum wheat, destructive growth analysis was carried out for every 14 days, to measure dry matter weight, leaf area index (LAI), plant population and, at harvest, yield components and grain quality. The results indicated that OMWW without pre-treatments spread on a durum wheat crop during vegetative phase produced some necrosis of the leaves and caused a slow emission of secondary stems. However, in this stage, durum wheat showed good capability to recover. Plant dry matter accumulation was not significantly influenced by OMWW spreading since it occurred at the beginning of the vegetative stage, when plants grow quickly. No significant differences, neither for grain nor for straw yield, between the two treatments were highlighted. The results of 3 years of experiments showed that the durum wheat crop can tolerate OMWW spreading during early growing stages. Great care should be used in spreading the wastewater uniformly on the soil, respecting the laws about soil capability to endure OMWW application.

title: Fungicidal effect of hydroxytyrosol-rich preparations from olive mill wastewater against Verticillium dahliae.
abstract: Verticillium dahliae cannot be reached by many fungicides during its parasitic phase inside the plants and few fungicides are available to cure plants once they are infected by this pathogen. A hydroxytyrosol-rich (29.27% weight/dry weight) olive mill wastewater (HROMW) and a hydroxytyrosol-rich (52.67% weight/dry weight) extract (HRE) were prepared from fresh olive mill wastewater (FOMW) using hydrolysis and post-hydrolysis purification processes, and were tested as bio-fungicides. The HROMW and HRE showed strong fungicidal activity in vitro against V. dahliae with minimal fungicidal concentrations (MFCs) of 28–56 mg L−1 (dry weight). The HROMW and HRE at 15 g L−1 (dry weight) resulted in a reduction in the viability of V. dahliae by >4 log units after 30 min of contact time according to European Standard EN 1275 (1997) standard method. In tomato pot growth experiments incorporation of HROMW and HRE into the soil reduced significantly Verticillium wilt disease incidence by 86 and 83% and wilt severity by 86 and 84.5%, respectively, compared to untreated plants.

title: Efficacy of a hydroxytyrosol-rich preparation from olive mill wastewater for control of olive psyllid, Euphyllura olivina, infestations
abstract: Olive mill wastewater (OMW) is a problematic by-product in Mediterranean countries. Despite this, it is a raw material that is an unfailing source of bioactive molecules. A hydroxytyrosol-rich preparation (HRP) (49.6% weight:dry weight) was extracted from fresh OMW using a hydrolysis and post-hydrolysis purification process. The field efficacy of HRP as a spray treatment (2500 l ha −1 ) against olive psyllid, Euphyllura olivina (Hemiptera: Psyllidae), was evaluated in 2008 and 2009 in a drip-irrigated olive orchard. The HRP showed strong insecticidal activity against E . olivina at a concentration of 2 g l −1 hydroxytyrosol. Application of HRP resulted in 41.1 and 72.1% control of nymphs and adults, respectively. However, HRP application did not reduce egg hatch. Neither phytotoxicity nor toxicity to auxiliary-fauna was recorded with concentrations of 1.25 g l −1 or 2 g l −1 HRP. But, the 2.5 g l −1 concentration was slightly phytotoxic, especially at the E and F floral phenological stages of the grapes. HRP offers a natural and effective extract for control of olive psyllid and opens a new opportunity for the reuse of OMW.

title: Biological activity of high molecular weight phenolics from olive mill wastewater.
abstract: Olive oil production generates large amounts of recalcitrant compounds, the olive oil mill wastewater (OMWW), which represent one of the most contaminating effluents among those produced by the agrofood industries. Nowadays, this view has changed to one that recognizes the waste as a low-cost starting material rich in bioactive compounds, particularly biophenols, that can be extracted and applied as natural antioxidants for the food and pharmaceutical industries. The data reported in this paper indicate that the OMWW extracts, besides low molecular weight antioxidant phenolics such as tyrosol and hydroxytyrosol, also contain phenolics with a molecular weight in the range of 600-5000 Da, which exhibit efficient scavenging activities against hydroxyl and peroxyl radicals. This group of phenolics includes, besides verbascoside, isoverbascoside, and an oxidized form of verbascoside, a number of higher molecular weight phenolics arising from oxidative polymerization of hydroxytyrosol and caffeic acid. Overall, these higher molecular weight phenolics prove to be, in some in vitro tests, more efficient scavengers of hydrophilic hydroxyl radicals than hydroxytyrosol, which could be used for industrial applications as natural nontoxic antioxidants.

title: Understanding Soil Microbes and Nutrient Recycling
abstract: Soil Microbes and Nutrient Recycling Soil microorganisms exist in large numbers in the soil as long as there is a carbon source for energy. A large number of bacteria in the soil exists, but because of their small size, they have a smaller biomass. Actinomycetes are a factor of 10 times smaller in number but are larger in size so they are similar in biomass to bacteria. Fungus population numbers are smaller but they dominate the soil biomass when the soil is not disturbed. Bacteria, actinomycetes, and protozoa are hardy and can tolerate more soil disturbance than fungal populations so they dominate in tilled soils while fungal and nematode populations tend to dominate in untilled or no-till soils. There are more microbes in a teaspoon of soil than there are people on the earth. Soils contain about 8 to 15 tons of bacteria, fungi, protozoa, nematodes, earthworms, and arthropods. See fact sheets on Roles of Soil Bacteria, Fungus, Protozoa and Nematodes. Microbial Soil Organic Matter Decomposition Organic matter decomposition serves two functions for the microorganisms, providing energy for growth and suppling carbon for the formation of new cells. Soil organic matter (SOM) is composed of the “living” (microorganisms), the “dead” (fresh residues), and the “very dead” (humus) fractions. The “very dead” or humus is the long-term SOM fraction that is thousands of years old and is resistant to decomposition. Soil organic matter has two components called the active (35%) and the passive (65%) SOM. Active SOM is composed of the “living” and “dead” fresh plant or animal material which is food for microbes and is composed of easily digested sugars and proteins. The passive SOM is resistant to decomposition by microbes and is higher in lignin. Microbes need regular supplies of active SOM in the soil to survive in the soil. Long-term no-tilled soils have significantly greater levels of microbes, more active carbon, more SOM, and more stored carbon than conventional tilled soils. A majority of the microbes in the soil exist under starvation conditions and thus they tend to be in a dormant state, especially in tilled soils. Dead plant residues and plant nutrients become food for the microbes in the soil. Soil organic matter (SOM) is basically all the organic substances (anything with carbon) in the soil, both living and dead. SOM includes plants, blue green algae, microorganisms (bacteria, fungi, protozoa, nematodes, beetles, springtails, etc.) and the fresh and decomposing organic matter from plants, animals, and microorganisms. Understanding Soil Microbes and Nutrient Recycling

title: Soil carbon change and its responses to agricultural practices in Australian agro-ecosystems: A review and synthesis
abstract: Soil is the largest reservoir of carbon (C) in the terrestrial biosphere and a slight variation in this pool could lead to substantial changes in the atmospheric CO 2 concentration, thus impact significantly on the global climate. Cultivation of natural ecosystems has led to marked decline in soil C storage, such that conservation agricultural practices (CAPs) are widely recommended as options to increase soil C storage, thereby mitigating climate change. In this review, we summarise soil C change as a result of cultivation worldwide and in Australia. We then combine the available data to examine the effects of adopting CAPs on soil C dynamics in Australian agro-ecosystems. Finally, we discuss the future research priorities related to soil C dynamics. The available data show that in Australian agro-ecosystems, cultivation has led to C loss for more than 40 years, with a total C loss of approximately 51% in the surface 0.1 m of soil. Adoption of CAPs generally increased soil C. Introducing perennial plants into rotation had the greatest potential to increase soil C by 18% compared with other CAPs. However, the same CAPs could result in different outcomes on soil C under different climate and soil combinations. No consistent trend of increase in soil C was found with the duration of CAP applications, implying that questions remain regarding long-term impact of CAPs. Most of the available data in Australia are limited to the surface 0.1 to 0.3 m of soil. Efforts are needed to investigate soil C change in deeper soil layers in order to understand the impact of crop root growth and various agricultural practices on C distribution in soil profile. Elevated atmospheric CO 2 concentration, global warming and rainfall change could all alter the C balance of agricultural soils. Because of the complexity of soil C response to management and environmental factors, a system modelling approach supported by sound experimental data would provide the most effective means to analyse the impact of different management practices and future climate change on soil C dynamics.

title: Incorporating organic matter alters soil greenhouse gas emissions and increases grain yield in a semi-arid climate
abstract: Increasing soil organic matter (OM) is promoted as a strategy for improving the resilience of coarse-textured cropping soils in semi-arid climates. While increasing soil OM can benefit crop productivity, it can also enhance nitrous oxide (N2O) emissions in temperate climates. Our objective was to investigate if increasing soil OM affected soil greenhouse gas (GHG) fluxes and grain production in a semi-arid region in south-western Australia. We firstly measured N2O and methane (CH4) fluxes from a free-draining sandy soil with contrasting soil OM content for 2.5 years using automated soil chambers. The randomized block design included two OM additions (no OM, plus OM) by two nitrogen (N) fertilizer rates (0, 0N; 100 kg N ha−1 yr−1, +N) by three replicate plots. Organic matter (chaff) had been applied to the plus OM treatments every three years since 2003, with 80 t OM ha−1 applied in total. Secondly, we investigated the interaction between soil OM content and N fertilizer addition on grain yield for two growing seasons. The randomized split-plot design included two OM treatments by five N fertilizer rates (0, 25, 50, 75 and 100 kg N ha−1), by three replicates. Increasing soil OM increased grain yields and soil mineral N, but also enhanced soil N2O emissions. Nitrous oxide emissions were low by international standards ( plus OM (0N; 194 g N2O-N ha−1) > no OM (+N; 41 g N2O-N ha−1) = no OM (0N; 14 g N2O-N ha−1). Increasing soil OM also decreased CH4 uptake by 30%. Management practices that increase soil OM in sandy-textured rainfed, cropping soils in semi-arid regions should be encouraged as they can improve grain yield without substantial increases in soil N2O or CH4 emissions.