Predicting the Structure of Enzymes with Metal Cofactors: The Example of [FeFe] Hydrogenases

The advent of deep learning algorithms for protein folding opened a new era in the ability of predicting and optimizing the function of proteins once the sequence is known. The task is more intricate when cofactors like metal ions or small ligands are essential to functioning. In this case, the combined use of traditional simulation methods based on interatomic force fields and deep learning predictions is mandatory. We use the example of [FeFe] hydrogenases, enzymes of unicellular algae promising for biotechnology applications to illustrate this situation. [FeFe] hydrogenase is an iron-sulfur protein that catalyzes the chemical reduction of protons dissolved in liquid water into molecular hydrogen as a gas. Hydrogen production efficiency and cell sensitivity to dioxygen are important parameters to optimize the industrial applications of biological hydrogen production. Both parameters are related to the organization of iron-sulfur clusters within protein domains. In this work, we propose possible three-dimensional structures of Chlorella vulgaris 211/11P [FeFe] hydrogenase, the sequence of which was extracted from the recently published genome of the given strain. Initial structural models are built using: (i) the deep learning algorithm AlphaFold; (ii) the homology modeling server SwissModel; (iii) a manual construction based on the best known bacterial crystal structure. Missing iron-sulfur clusters are included and microsecond-long molecular dynamics of initial structures embedded into the water solution environment were performed. Multiple-walkers metadynamics was also used to enhance the sampling of structures encompassing both functional and non-functional organizations of iron-sulfur clusters. The resulting structural model provided by deep learning is consistent with functional [FeFe] hydrogenase characterized by peculiar interactions between cofactors and the protein matrix.

Improved Cardiovascular Effects of a Novel Pomegranate Byproduct Extract Obtained through Hydrodynamic Cavitation

The healthy properties of pomegranate fruit, a highly consumed food, have been known for a long time. However, the pomegranate supply chain is still rather inefficient, with the non-edible fraction, whose weight is roughly half the total and is endowed with plenty of valuable bioactive compounds, either disposed of or underutilized. A novel extract obtained from non-edible byproducts (called PPE), using hydrodynamic cavitation, a green, efficient, and scalable technique, was investigated for its cardiovascular effects in vivo. PPE showed efficacy in an acute phenylephrine (PE)-induced hypertensive rat model, similar to the extract of whole fruit (PFE) obtained using the same extractive technique, along with good intestinal bioaccessibility after oral administration. Finally, when chronically administered for 6 weeks to spontaneously hypertensive rats, PPE was shown to significantly contain the increase in systolic blood pressure, comparable to the reference drug Captopril, and at a dose remarkably lower than the reported effective dose of ellagic acid. The extract from the non-edible fraction of the pomegranate fruit also showed good anti-inflammation and anti-fibrotic effects. The findings of this study, along with the extraction technique, could contribute to enhancing the value of the pomegranate supply chain, relieve the related environmental burden, and potentially improve public health.

Valuable pigments from microalgae: phycobiliproteins, primary carotenoids, and fucoxanthin

Phycobiliproteins, carotenoids and fucoxanthin are photosynthetic pigments extracted from microalgae and cyanobacteria with great potential biotechnological applications, as healthy food colorants and cosmetics. Phycocyanin possesses a brilliant blue color, with fluorescent properties making it useful as a reagent for immunological essays. The most important source of phycocyanin is the cyanobacterium Arthrospira platensis, however, recently, the Rhodophyta Galdieria sulphuraria has also been identified as such. The main obstacle to the commercialization of phycocyanin is represented by its chemical instability, strongly reducing its shelf-life. Moreover, the high level of purity needed for pharmaceutical applications requires several steps which increase both the production time and cost. Microalgae (Chlorella, Dunaliella, Nannochloropsis, Scenedesmus) produce several light harvesting carotenoids, and are able to manage with oxidative stress, due to their free radical scavenging properties, which makes them suitable for use as source of natural antioxidants. Many studies focused on the selection of the most promising strains producing valuable carotenoids and on their extraction and purification. Among carotenoids produced by marine microalgae, fucoxanthin is the most abundant, representing more than 10% of total carotenoids. Despite the abundance and diversity of fucoxanthin producing microalgae only a few species have been studied for commercial production, the most relevant being Phaeodactylum tricornutum. Due to its antioxidant activity, fucoxanthin can bring various potential benefits to the prevention and treatment of lifestyle-related diseases. In this review, we update the main results achieved in the production, extraction, purification, and commercialization of these important pigments, motivating the cultivation of microalgae as a source of natural pigments.

Evaluation of the Fruit Quality and Phytochemical Compounds in Peach and Nectarine Cultivars

Qualitative traits and chemical properties of 32 peach cultivars (yellow flesh and white flesh fruits) and 52 nectarine cultivars (yellow flesh and white flesh fruits) of different pomological characteristics is performed, and the correlation between cultivars and chemical characteristics is analyzed. Yellow nectarines have a higher variability in soluble solids concentration (SSC) and titratable acidity (TA) values. Evaluation of color parameters (a*, b*, L*) shows a significant interaction between pulp color (white vs. yellow) and types (peaches vs. nectarines) of fruit. The difference between yellow and white fruits is stronger in nectarines than in peaches. Sucrose is the main sugar detected in peach fruits, with a percentage content of 78.37% and 76.70% of the total sugar content in yellow and white peaches, respectively, and 78.29% and 78.12% in yellow and white nectarines, respectively. Variability is found among cultivars for the chemical compounds analyzed. The yellow flesh has higher amounts of total carotenoids and TPC, while white-flesh fruits present an average antioxidant value higher than yellow-flesh fruits. No significant correlation is found for polyphenol content and DPPH, while an interaction (p < 0.005) between neochlorogenic acid content and peaches and nectarines is evidenced, with a neochlorogenic acid content higher in nectarines than in peaches.

New Route to the Production of Almond Beverages Using Hydrodynamic Cavitation

Perceived as a healthy food, almond beverages are gaining ever-increasing consumer preference across nonalcoholic vegetable beverages, ranking in first place among oilseed-based drinks. However, costly raw material; time and energy consuming pre- and posttreatments such as soaking, blanching and peeling; and thermal sterilization hinder their sustainability, affordability and spread. Hydrodynamic cavitation processes were applied, for the first time, as a single-unit operation with straightforward scalability, to the extraction in water of almond skinless kernels in the form of flour and fine grains, and of whole almond seeds in the form of coarse grains, up to high concentrations. The nutritional profile of the extracts matched that of a high-end commercial product, as well as showing nearly complete extraction of the raw materials. The availability of bioactive micronutrients and the microbiological stability exceeded the commercial product. The concentrated extract of whole almond seeds showed comparatively higher antiradical activity, likely due to the properties of the almond kernel skin. Hydrodynamic cavitation-based processing might represent a convenient route to the production of conventional as well as integral and potentially healthier almond beverages, avoiding multiple technological steps, while affording fast production cycles and consuming less than 50 Wh of electricity per liter before bottling.

Tanacetum species: Bridging empirical knowledge, phytochemistry, nutritional value, health benefits and clinical evidence

Introduction: The Tanacetum genus consists of 160 accepted flowering species thriving throughout temperate regions, mainly in the Mediterranean Basin, Northern America, and southwestern and eastern Asia. Tanacetum species bear a long-standing record of use in the folk medicine of indigenous tribes and communities worldwide, along with multitudinous applications in traditional cuisines, cosmeceuticals, and agricultural fields. Methods: Up-to-date data related to traditional uses, phytochemistry, biological activities, toxicity and clinical trials of the genus Tanacetum were systematically reviewed from several online scientific engines, including PubMed, Web of Science, Scopus, SciFinder, Wiley Online, Science Direct, and Cochrane library. Results and discussion: Over the past three decades, 241 metabolites have been isolated from nearly twenty species, including phenolic acids, flavonoids, coumarins, fatty acids and alkanes, aldehydes, volatile compounds, and naphthoquinones. Some unique metabolites have also been identified, such as the ceramides tanacetamide (A-D) from T. artemisioides, pyrethrins from T. cinerariifolium, and sesquiterpene lactones from several species. However, these secondary metabolites are still poorly studied despite in vitro clues highlighting their colossal pharmacological properties, especially as hypotensive, neuroprotective, anticancer, and antimicrobial agents. Scientific studies have validated some traditional claims of the plant, such as antidiabetic, anticancer, anthelmintic, insecticide, antioxidant, and hepatoprotective activities, as well as against festering wounds, skin ulcers, urinary tract infections, and sexually transmitted diseases. Other ethnomedicinal uses for arthritis, gout, rheumatism, anemia, and as a litholytic, antivenom and diaphoretic have not yet been supported and would constitute the subject of further research.

Characterization of the (Poly)Phenolic Fraction of Fig Peel: Comparison among Twelve Cultivars Harvested in Tuscany

(1) Background: The fig tree (Ficus carica L.) is widely cultivated in the Mediterranean area and it produces fruits largely consumed in the Mediterranean diet. Previous studies have shown that this fruit represents a rich source of (poly)phenols, which are mainly located in the peel rather than the pulp. In our study, fig peel derived from twelve different cultivars located in Tuscany was assessed for its (poly)phenol profile. (2) Methods: The (poly)phenol characterization was performed through ultra-high performance liquid chromatography coupled to multiple-stage mass spectrometry. (3) Results: Twenty-eight (poly)phenolic compounds were quantified in the investigated fig peel. It was possible to observe an interesting variability in the (poly)phenol content among the twelve cultivars of fig peel. Rutin and 5-caffeoylquinic acid were the main compounds in the greenish fig peel, while cyanidin-3-O-rutinoside was the main component in the dark-violet fig peel. (4) Conclusions: fig peel could be used as a (poly)phenol-rich ingredient in several food products to increase the bioactive compound content of foods. Moreover, dark-violet peel could be considered potentially suitable as a natural food colorant.

The Potential of the Marine Microalga Diacronema lutheri in the Prevention of Obesity and Metabolic Syndrome in High-Fat-Fed Wistar Rats

Long-chain polyunsaturated fatty acids n-3 series (n-3 LC-PUFAs), especially eicosapentaenoic and docosahexaenoic acids, are known to exert preventive effects on obesity and metabolic syndrome. Mainly consumed in the form of fish oil, LC-PUFAs n-3 are also found in significant quantities in other sources such as certain microalgae. The aim of this study was to evaluate the effects of Diacronema lutheri (Dia), a microalga rich in n-3 LC-PUFAs, on metabolic disorders associated with obesity. Three groups of male Wistar rats (n = 6 per group) were submitted for eight weeks to a standard diet or high-fat and high-fructose diet (HF), supplemented or not with 12% of Dia (HF-Dia). Compared to HF rats, HF-Dia rats showed a 41% decrease in plasma triacylglycerol (TAG) and an increase in plasma cholesterol (+35%) as well as in high-density lipoprotein cholesterol (+51%) without change to low-density lipoprotein cholesterol levels. Although fasting glycemia did not change, glucose and insulin tolerance tests highlighted an improvement in glucose and insulin homeostasis. Dia supplementation restored body weight and fat mass, and decreased levels of liver TAG (−75%) and cholesterol (−84%). In HF-Dia rats, leptin was decreased (−30%) below the control level corresponding to a reduction of 68% compared to HF rats. Similarly, the anti-inflammatory cytokines interleukin-4 (IL-4) and IL-10 were restored up to control levels, corresponding to a 74% and 58% increase in HF rats, respectively. In contrast, the level of IL-6 remained similar in the HF and HF-Dia groups and about twice that of the control. In conclusion, these results indicated that the D. lutheri microalga may be beneficial for the prevention of weight gain and improvement in lipid and glucose homeostasis.

In situ monitoring of chlorophyll a fluorescence in Nannochloropsis oceanica cultures to assess photochemical changes and the onset of lipid accumulation during nitrogen deprivation

In situ chlorophyll a fluorescence measurements were applied to monitor changes in the photochemical variables of Nannochloropsis oceanica cultures under nitrogen-deplete and nitrogen-replete (control) conditions. In addition, growth, lipid, fatty acid, and pigment contents were also followed. In the control culture, growth was promoted along with pigment content, electron transport rate (ETR), and polyunsaturated fatty acids, while total lipid content and fatty acid saturation level diminished. Under nitrogen-deplete conditions, the culture showed a higher de-epoxidation state of the xanthophyll cycle pigments. Fast transients revealed a poor processing efficiency for electron transfer beyond Q_A , which was in line with the low ETR due to nitrogen depletion. Lipid content and the de-epoxidation state were the first biochemical variables triggered by the change in nutrient status, which coincided with a 20% drop in the in situ effective quantum yield of PSII (ΔF'/F_m '), and a raise in the V_j measurements. A good correlation was found between the changes in ΔF'/F_m ' and lipid content (r = -0.96, p < 0.01). The results confirm the reliability and applicability of in situ fluorescence measurements to monitor lipid induction in N. oceanica.

Preventive Effects of the Marine Microalga Phaeodactylum tricornutum, Used as a Food Supplement, on Risk Factors Associated with Metabolic Syndrome in Wistar Rats

Long-chain polyunsaturated fatty acids, n-3 series (n-3 LC-PUFA), are known for their preventive effects against cardiovascular disease. In an unfavourable economic and environmental context of fish oil production, marine microalgae could be an alternative source of n-3 LC-PUFA and are of interest for human nutrition. The aim of this study was to evaluate the effects of P. tricornutum, a microalga rich in eicosapentaenoic acid and used as a food supplement, on the metabolic disorders associated with metabolic syndrome and obesity development. Three male Wistar rat groups (n = 6) were submitted for eight weeks to a standard diet or high-fat diet (HF) with 10% fructose in drinking water, supplemented or not with 12% of P. tricornutum (HF-Phaeo). Supplementation led to n-3 LC-PUFA enrichment of lipids in the liver, plasma and erythrocytes. Plasma transaminases showed no difference between the HF and HF-Phaeo groups. Body weight, fat mass, inflammatory markers and insulinemia decreased in HF-Phaeo rats versus the HF group. Plasma total cholesterol, triacylglycerols and leptine diminished in HF-Phaeo rats, while HDL-cholesterol increased. In conclusion, this study highlights the beneficial effects of P. tricornutum in reducing the metabolic disorders associated with metabolic syndrome.

Test procedures for measuring the (sub)chronic effects of chemicals on the freshwater cyclopoid Eucyclops serrulatus

The purpose of this study has been to describe test procedures for measuring the (sub)chronic effects of chemicals on the freshwater cyclopoid Eucyclops serrulatus. To this end we have adapted the setting of the standard full life-cycle protocol of the marine harpacticoid A. tenuiremis to E. serrulatus. We have tested the effects of 4 different diets, two temperatures and two rearing volumes on the survival, development, reproduction and population growth rates of this species. Our results have highlighted that full life-cycle tests can be run using 2 mL-glass vials, a diet consisting of a mixture of living cells of Chlorella sorokiniana and Scenedesmus quadricauda, at either 25 °C (test duration: 42 days) or 18 °C (test duration: 51 days). However, the best performance in terms of survival, development, reproducibility and population growth rates with this species was obtained at 18 °C, albeit with significantly longer test duration. Subchronic tests in 2 mL-glass vials with the mixture microalgal diet at both temperatures are available options if considered appropriate for the objectives of a given study. In particular, developmental tests from nauplius to copepodid may profitably be performed in about 11 days at 18 °C and in 6 days at 25 °C. Under the same test conditions, subchronic tests from copepodid to adult may be run in 19 days at 18 °C and in 16 days at 25 °C.

Acclimation strategy of Rhodopseudomonas palustris to high light irradiance

The ability of Rhodopseudomonas palustris cells to rapidly acclimate to high light irradiance is an essential issue when cells are grown under sunlight. The aim of this study was to investigate the photo-acclimation process in Rhodopseudomonas palustris 42OL under different culturing conditions: (i) anaerobic (AnG), (ii) aerobic (AG), and (iii) under H₂-producing (HP) conditions both at low (LL) and high light (HL) irradiances. The results obtained clearly showed that the photosynthetic unit was significantly affected by the light irradiance at which Rp. palustris 42OL was grown. The synthesis of carotenoids was affected by both illumination and culturing conditions. At LL, lycopene was the main carotenoid synthetized under all conditions tested, while at HL under HP conditions, it resulted the predominant carotenoid. Oppositely, under AnG and AG at HL, rhodovibrin was the major carotenoid detected. The increase in light intensity produced a deeper variation in light-harvesting complexes (LHC) ratio. These findings are important for understanding the ecological distribution of PNSB in natural environments, mostly characterized by high light intensities, and for its growth outdoors.

H2 production in Rhodopseudomonas palustris as a way to cope with high light intensities

The ability of coping with the damaging effects of high light intensity represents an essential issue when purple non-sulfur bacteria (PNSB) are grown under direct sunlight for photobiological hydrogen production. This study was aimed at investigating whether H2 photo-evolution could represent, for Rhodopseudomonas palustris 42OL, a safety valve to dissipate an excess of reducing power generated under high light intensities. The physiological status of this strain was assessed under anaerobic (AnG) and aerobic (AG) growing conditions and under H2-producing (HP) conditions at low and high light intensities. The results obtained clearly showed that Fv/Fm ratio was significantly affected by the light intensity under which R. palustris 42OL cells were grown, under either AnG or AG conditions, while, under HP, it constantly remained at its highest value. The increase in light intensity significantly increased the H2 production rate, which showed a positive correlation with the maximum electron transfer rate (rETRmax). These findings are important for optimization of hydrogen production by PNSB under solar light.

Innovative method for recovery and valorization of hydroxytyrosol from olive mill wastewaters

The nutritional properties of olive oil can be attributed to its oleic acid and phenolic compounds content, acting as natural oxidants to prevent human diseases. In particular, hydroxytyrosol has an anti-inflammatory action similar to omega 3 fatty acids from fish oil. The olive oil production was conducted by two extraction procedures: first, a two-phase extraction giving extra-virgin olive oil and humid pomace, second, a three-phase working process of humid pomace, obtaining another minimum quantity of extra-virgin olive oil, 'dry' pomace devoid of polyphenols, and mill wastewaters rich in anti-oxidant compounds. The aim of this processing was to employ water to extract the highest concentration of polyphenols from humid pomace and convey them in oil mill wastewaters for extraction. Processed olives were 37,200 kg, pomace deprived of polyphenols was equal to 20,400 kg and processing was performed with 500 kg of olives per hour. This method offers advantages of using cheap equipment and technical simplicity.

Advances in the biotechnology of hydrogen production with the microalga Chlamydomonas reinhardtii

Biological hydrogen production is being evaluated for use as a fuel, since it is a promising substitute for carbonaceous fuels owing to its high conversion efficiency and high specific energy content. The basic advantages of biological hydrogen production over other "green" energy sources are that it does not compete for agricultural land use, and it does not pollute, as water is the only by-product of the combustion. These characteristics make hydrogen a suitable fuel for the future. Among several biotechnological approaches, photobiological hydrogen production carried out by green microalgae has been intensively investigated in recent years. A select group of photosynthetic organisms has evolved the ability to harness light energy to drive hydrogen gas production from water. Of these, the microalga Chlamydomonas reinhardtii is considered one of the most promising eukaryotic H2 producers. In this model microorganism, light energy, H2O and H2 are linked by two excellent catalysts, the photosystem 2 (PSII) and the [FeFe]-hydrogenase, in a pathway usually referred to as direct biophotolysis. This review summarizes the main advances made over the past decade as an outcome of the discovery of the sulfur-deprivation process. Both the scientific and technical barriers that need to be overcome before H2 photoproduction can be scaled up to an industrial level are examined. Actual and theoretical limits of the efficiency of the process are also discussed. Particular emphasis is placed on algal biohydrogen production outdoors, and guidelines for an optimal photobioreactor design are suggested.

Unusual catalysts from molasses: synthesis, properties and application in obtaining biofuels from algae

Acid catalysts were prepared by sulfonation of carbon materials obtained from the pyrolysis of sugar beet molasses, a cheap, viscous byproduct in the processing of sugar beets into sugar. Conditions for the pyrolysis of molasses (temperature and time) influenced catalyst performance; the best combination came from pyrolysis at low temperature (420 °C) for a relatively long time (8-15 h), which ensured better stability of the final material. The most effective molasses catalyst was highly active in the esterification of fatty acids with methanol (100 % yield after 3 h) and more active than common solid acidic catalysts in the transesterification of vegetable oils with 25-75 wt % of acid content (55-96 % yield after 8 h). A tandem process using a solid acid molasses catalyst and potassium hydroxide in methanol was developed to de-acidificate and transesterificate algal oils from Chlamydomonas reinhardtii, Nannochloropsis gaditana, and Phaeodactylum tricornutum, which contain high amounts of free fatty acids. The amount of catalyst required for the de-acidification step was influenced by the chemical composition of the algal oil, thus operational conditions were determined not only in relation to free fatty acids content in the oil, but according to the composition of the lipid extract of each algal species.

Preliminary investigation on the production of fuels and bio-char from Chlamydomonas reinhardtii biomass residue after bio-hydrogen production

The aim of this work was to investigate the potential conversion of Chlamydomonas reinhardtii biomass harvested after hydrogen production. The spent algal biomass was converted into nitrogen-rich bio-char, biodiesel and pyrolysis oil (bio-oil). The yield of lipids (algal oil), obtained by solvent extraction, was 15 ± 2% w/w(dry-biomass). This oil was converted into biodiesel with a 8.7 ± 1% w/w(dry-biomass) yield. The extraction residue was pyrolysed in a fixed bed reactor at 350 °C obtaining bio-char as the principal fraction (44 ± 1% w/w(dry-biomass)) and 28 ± 2% w/w(dry-biomass) of bio-oil. Pyrolysis fractions were characterized by elemental analysis, while the chemical composition of bio-oil was fully characterized by GC-MS, using various derivatization techniques. Energy outputs resulting from this approach were distributed in hydrogen (40%), biodiesel (12%) and pyrolysis fractions (48%), whereas bio-char was the largest fraction in terms of mass.

Outdoor H₂ production in a 50-L tubular photobioreactor by means of a sulfur-deprived culture of the microalga Chlamydomonas reinhardtii

In the past decade, H₂ production using the green microalga Chlamydomonas reinhardtii has been extensively studied under laboratory-scale photobioreactors, while information on outdoor cultures is still lacking. In this paper, the results of experiments conducted with sulfur-deprived cultures of C. reinhardtii carried out in a 50-L horizontal tubular photobioreactor are presented. Hydrogen production experiments were carried out under both artificial and direct solar light. In both cases, the H₂ output attained was 18-20% of what obtained in the laboratory. However, no significant changes in the H₂ production were observed when cells grown outdoors were tested under laboratory conditions. Chlorophyll fluorescence measurements showed that outdoor cultures were subjected to strong photo-inhibition, due to the combination of high solar light intensity and sulfur-deprivation. Indeed, H₂ production was only achieved outdoors when cultures were previously acclimated to sunlight, a condition that caused a number of physiological changes, namely: (i) a decrease in the chlorophyll content per unit of dry weight; (ii) an increase in the photosynthesis and respiration rates, and (iii) a higher induction of the xanthophyll cycle pigments as compared to non-acclimated cultures. It was concluded that the reduced H₂ output achieved in the 50-L photobioreactor was due to the different illumination pattern to which the cultures were exposed (one-sided vs. two-sided illumination provided in the laboratory), as well as to the great difference in the mixing times (60 min vs. 15.5s achieved in the lab-scale photobioreactor). To the very best of our knowledge this is the first time that H₂ production with green algae has been achieved by means of solar light.

Antioxidant defences and oxidative damage in salt-treated olive plants under contrasting sunlight irradiance

The interactive effects of root-zone salinity and sunlight on leaf biochemistry, with special emphasis on antioxidant defences, were analysed in Olea europaea L. cv. Allora, during the summer period. Plants were grown outside under 15% (shade plants) or 100% sunlight (sun plants) and supplied with 0 or 125 mM NaCl. The following measurements were performed: (1) the contribution of ions and soluble carbohydrates to osmotic potentials; (2) the photosystem II (PSII) photochemistry and the photosynthetic pigment concentration; (3) the concentration and the tissue-specific distribution of leaf flavonoids; (4) the activity of antioxidant enzymes; and (5) the leaf oxidative damage. The concentrations of Na(+) and Cl(-) were significantly greater in sun than in shade leaves, as also observed for the concentration of the 'antioxidant' sugar-alcohol mannitol. The de-epoxidation state of violaxanthin-cycle pigments increased in response to salinity stress in sun leaves. This finding agrees with a greater maximal PSII photochemistry (F(v)/F(m)) at midday, detected in salt-treated than in control plants, growing in full sunshine. By contrast, salt-treated plants in the shade suffered from midday depression in F(v)/F(m) to a greater degree than that observed in control plants. The high concentration of violaxanthin-cycle pigments in sun leaves suggests that zeaxanthin may protect the chloroplast from photo-oxidative damage, rather than dissipating excess excitation energy via non-photochemical quenching mechanisms. Dihydroxy B-ring-substituted flavonoid glycosides accumulate greatly in the mesophyll, not only in the epidermal cells, in response to high sunlight. The activity of antioxidant enzymes varied little because of sunlight irradiance, but declined sharply in response to high salinity in shade leaves. Interestingly, control and particularly salt-treated plants in the shade underwent greater oxidative damage than their sunny counterparts. These findings, which conform to the evolution of O. europaea in sunny environments, suggest that under partial shading, the antioxidant defence system may be ineffective to counter salt-induced oxidative damage.

An eco-compatible process for the depuration of wastewater from olive mill industry

Olive mill wastewater (OMW) is the by-product of olive oil industrial production. It is characterized by a dark brownish color and a strong odor and is considered one of the most polluted agricultural wastes. In this paper we briefly describe an innovative procedure for the depuration of olive mill wastewater. With this procedure it is also possible to recover valuable substances such as phenolic compounds which have important commercial applications: they can be used in the prevention of cardiovascular disease and as antiviral, antioxidant and antitumor agents. The proposed OMW treatment uses two different packed vegetable matrices which remove most of the pollutant substances by absorption. After filtration of OMW on the matrices the pollutant load of the waste is greatly reduced: the organic content (COD) is reduced more than 80% and the phenol compounds are completely removed.

Populations of exopolysaccharide-producing cyanobacteria and diatoms in the mucilaginous benthic aggregates of the Tyrrhenian Sea (Tuscan Archipelago)

The microalgal community of benthic mucilages sampled in various sites of the Tuscan Archipelago during the period May 1999-July 2002, was always dominated by diatoms. Synedra, Licmophora and Navicula were the most frequently found genera, their presence having been observed within all the period under study; other ten genera of diatoms were found in the benthic mucilages, but their presence was dependent on the month and the year of observation. As concerns the cyanobacterial community, the filamentous genera Leptolyngbya, Lyngbya and Rivularia were the most frequently found, independently on the period and the year of samplings, while other genera, namely Oscillatoria, Symploca, Aphanocapsa and Gloeocapsa, were less frequently observed. During the period under study, the highest number of different genera of diatoms and cyanobacteria in the mucilaginous aggregates was observed during summer periods, particularly in June and July. The microscopic observation of the samples demonstrated that only diatoms belonging to the genera Navicula, Amphora, Cylindrotheca and Pseudo-nitzschia possessed outermost polysaccharidic investments, the cells of the other genera being devoid of sheaths or capsules. On the other side, all the observed cyanobacteria, with the exception of Oscillatoria strains, were characterized by the presence of outermost polysaccharidic investments, most frequently in the form of sheaths. However, when the microalgal and cyanobacterial isolates were cultured under laboratory conditions, the release of polysaccharidic material into the culture medium was observed only in a few cases and always in very small amounts. The observations done on the natural samples and the results obtained with the cultures of the microalgae and cyanobacteria isolated from the benthic aggregates suggest that only diatoms have given some contribution to the formation of the polysaccharidic material constituting the matrix of the mucilages, whereas the role of cyanobacteria in the benthic aggregates seems to be related to their capability to create biofilms on solid surfaces, constituting the first step in the colonization of the benthic surfaces by the microbial community.