Helena Pereira

University of Lisbon | UL · Forest Research Center (CEF)

Recently, more and more researchers have begun to consider using waste bark fractions to produce value-added biochemicals and materials, as well as for energy production. Extraction is often the first operation in biomass biorefineries. Here we obtained hydroethanolic extracts from waste cork and phloem fractions of Quercus cerris bark and analyzed...

The Miombo species Parinari curatellifolia has a bark with a cork-rich rhytidome that was studied here for the first time regarding extract yields and composition, using the complete rhytidome and also the separated cork fraction. The objective was to analyse their potential as sources of extracts with antioxidant activities aiming at increasing th...

Pine nutshells (PNSs) are lignocellulosic waste materials with limited use in domestic heating. However, a biorefinery approach may be applied to fractionate PNSs and produce chemicals, materials, and improved solid fuels. In this study, we fractionated PNSs and produced antioxidant extracts, lignins, polysaccharides, chars, and activated carbons a...

The bioactive properties of underutilized corks such as Quercus cerris cork and planted Quercus suber cork in the Eastern Mediterranean are not well-known but are crucial in developing lignocellulosic biorefineries. To assess their biological potential, hydroethanolic cork extracts of Quercus cerris and Quercus suber were analyzed for phenolic comp...

A comprehensive analysis of outdoor weathering and soil burial of cork during 1-year experiments was carried out with measurements of CIELAB color parameters, cellular observations by scanning electron microscopy, and surface chemical features analysed by ATR-FTIR and wet chemical analysis. Cork applied in outdoor conditions above and below ground...

Dear Colleagues, The utilization of woody biomass for energy conversion involves employing advanced technologies to extract energy efficiently from organic materials such as forestry residues and agricultural waste. This process, driven by the need for sustainable energy sources, includes various thermochemical and biochemical pathways, such as py...

The present study highlights, for the first time, the chemical composition of secondary metabolites (lipophilic and hydrophilic compounds) present in the phloem tissues of infected mature Pinus pinaster Ait. trees (on average 74 years old), which may be potentially determinant in the development of the pine wood nematode (PWN) Bursaphelenchus xylop...

The production of high-value products from microalgae, one of the preferred emerging biorefineries’ feedstocks, relies on the crucial step of biomass fractionation. In this work, the fractionation of Chlorella vulgaris and Scenedesmus obliquus biomass was tested for protein extraction using a wide range of physical, chemical, and enzymatic treatmen...

Pine nut shells, a biomass residue from the Mediterranean Pinus pinea pine nut industrial processing, were treated by microwave-assisted autohydrolysis to produce xylo-oligosaccharides. Microwave-assisted processes provide alternative heating that may reduce energy input and increase overall process efficiency. The autohydrolysis treatments were pe...

The detailed anatomical and chemical features of the bark from endemic Quercus vulcanica in Turkey are reported here for the first time and discussed in the perspective of integration into a bark-based biorefinery system. The bark of Q. vulcanica trees was collected and studied through observations using light and scanning electron microscopy, wet-...

The wood colour variability of 98 tropical species from India (Goa), Mozambique and East Timor was described using CIELab colour parameters and related to wood density and anatomical features. Wood colours were mostly light and yellowish, ranging from 24.0–84.4 for wood lightness, 2.6–20.4 for redness, 1.8–36.6 for yellowness, 2.1–35.9 for chromati...

Bark is a heterogeneous solid material comprising mainly of phloem and cork fractions. These fractions differ in chemical composition and anatomical structure, and value-added activated carbons produced from these fractions have different surface properties. Low-temperature pyrolysis was shown to be a promising method for producing activated carbon...

Parinari curatellifolia is an important evergreen tree from the Miombo woodland of south-central and eastern Africa. The bark is corky, suggesting an increased protection against the ecosystem high temperatures and drought conditions as well as against wild fires. The cork in the bark rhytidome of P. curatellifolia was analyzed here for the first t...

Taurus flowering ash (Fraxinus ornus subsp. cilicica) is an endemic tree species in Turkey. The bark of the species was characterized for summative chemical composition, the monomeric composition of polysaccharides, phenolic content, in vitro and ex vivo antioxidant properties of hydrophilic extracts, the composition of lipophilic extractives and s...

This study presents for the first time an analysis of the content and chemical composition of the cuticular waxes and cutin in the leaves of the widespread and important tropical species Terminalia catappa. The leaves were collected in the equatorial Atlantic islands of São Tomé and Príncipe, in the Gulf of Guinea. The epicuticular and intracuticul...

Waste-grade cork samples of Quercus cerris were subjected to maceration extraction using 7 different solvents, including pure water (I), pure acetone (II), 75% aqueous ethanol (III), 75% aqueous methanol (IV), 75% aqueous acetone (V), 50% aqueous acetone (VI), and 25% aqueous acetone (VII). The extract yields, extract compositions, as well as antio...

Pinus pinea nuts are commercial relevant Mediterranean edible forest nuts, with an increasing production and market value, whose industrial processing yields a lignocellulosic by-product, the pine nut shells, currently only used for combustion. Little research has been done on pine nut shells that could support a value-added application for this re...

Cork oak (Quercus suber L.) has high economic value given by its sustainable production of cork, and ecological importance in the Mediterranean region. The species is well adapted to the dry climate, namely through the sclerophyllous nature of its leaves with a well-developed cuticle, including cutin and cuticular waxes that contribute to protectio...

Cistus ladanifer (rockrose) is a widespread shrub species in the Mediterranean region well known due to its production of labdanum gum, especially in the hot season. Its leaves and branches can be subjected to different extraction and distillation processes to produce various types of extracts. The natural extracts of C. ladanifer have several appl...

Pinus pinea nuts are commercial relevant Mediterranean edible forest nuts, whose industrial processing yields a lignocellulosic by-product, the shells (PNS), currently only used for combustion. This work aims at its integrated upgrade within the biorefinery framework. Autohydrolysis was explored in the temperature range between 150 and 230 ºC (corr...

The cuticular lipid compounds, usually named cuticular waxes, present in the cuticular layering of Quercus suber adult leaves were extracted with solvents of different polarities (n-hexane, dichloromethane and acetone) and analysed by GC–MS. Q. suber leaves have a substantial cuticular wax layer (2.8% of leaf mass and 239 μg/cm2), composed predomin...

Tropical species are highly valued timber sources showing a large diversity of wood characteristics. Since there are major concerns regarding the sustainability of these tropical species in many tropical regions, knowledge of the variability in wood properties is therefore a valuable tool to design targeted exploitation and to enlarge the wood reso...

The beetle Coraebus undatus, during its larval stage feeds, and excavates galleries on the cork-generating layer of Quercus suber L. trees, seriously affecting the cork quality with significant economic losses for the cork industry. This work compared the composition of the extracts present in the innermost cork layers (the belly) of cork planks fr...

Grape pomace (grape skin and seeds) and stems are major by-products of winemaking, of lignocellulosic nature. The aim of this study was to value grape pomace and stems to produce prebiotic oligosaccharides (OS). Grapes from Touriga Nacional and Marselan cultivars (Vitis vinifera L.) were used for conventional red winemaking. The total of extractive...

Waste cork and phloem fractions from the bark of Turkey oak (Quercus cerris) were subject to low-temperature pyrolysis between 250 and 325 °C and residence times of 30 or 60 min. The fuel, leaching, and methylene blue adsorption properties of the produced biochars were evaluated for the first time. The results indicate that cork and phloem containi...

Quercus suber L. (cork oak) leaves were analyzed along one annual cycle for cuticular wax content and chemical composition. This species, well adapted to the long dry summer conditions prevailing in the Mediterranean, has a leaf life span of about one year. The cuticular wax revealed a seasonal variation with a coverage increase from the newly expa...

The bark of an Eucalyptus urophylla hybrid clone used by the charcoal industry was studied regarding anatomy and chemical composition, including the characterization of its polar extracts, in view of its potential use. The bark is characterized by a dominant homogeneous phloem with little ray expansion and alterations in the non-conducting phloem a...

In this study, glucan-rich solids, and xylose-rich hydrolysates obtained from Cistus ladanifer distillery residues (CLR) were used for d-lactic acid (d-LA) production by the d-lactogenic Escherichia coli strain JU15. Firstly, hemicellulosic hydrolysates obtained by the autohydrolysis process were submitted to dilute sulfuric acid-catalysed post-hyd...

Rockrose lignocellulosic residues (RR) were selectively fractionated for hemicellulose separation using autohydrolysis, followed by an alkaline treatment to solubilize the lignin. The cellulose-enriched solids were used to study the effect of solid loading (SL: 2–10%) and enzyme dosage (ED: 6.34–23.66 FPU/g dry biomass) on saccharification using a...

Cement production is among the most important contributors to global CO2 emissions. Partial replacement of cement with waste cork granules in mortars simultaneously enables the reduction of CO2 emissions and cork waste while achieving some improved material properties. Therefore, in the current study, cement content in the mortar formulations was p...

Olive pomace oil (OPO), a by-product of olive oil industry, is directly consumed after refining. The novelty of this study consists of the direct use of crude high acidic OPO (3.4–20% acidity) to produce added-value compounds, using sn-1,3-regioselective lipases: (i) low-calorie dietetic structured lipids (SL) containing caprylic (C8:0) or capric (...

Agonandra brasiliensis, ivory wood, is a tree species from the Brazilian cerrado with a bark featuring a thick cork layer. The present study aimed to describe the cellular features and chemical composition of this cork. The cork was investigated regarding cellular structure and biometry, as well as summative chemical composition. The results were c...

Introduction: Cutin is a biopolyester involved in waterproofing aerial plant organs, including leaves. Cutin quantification and compositional profiling require depolymerisation, namely by methanolysis, but specific protocols are not available. Objectives: Investigate how different methanolysis conditions regarding catalyst concentration effect c...

Tree barks are considerable waste streams in forest industries, and a potentially interesting resource for biorefineries. Barks of six relevant tree species, namely poplar (Populus × canadensis), black locust (Robinia pseudoacacia), red oak (Quercus rubra), willow (Salix sp.), Corsican pine (Pinus nigra subsp. laricio), and larch (Larix decidua), w...

This study analyzes the content and chemical profile of extractives present in the young phloem of mature trees of maritime pine (Pinus pinaster) and stone pine (P. pinea) in three sites in Portugal located in different climatic environments. The cross-sites average of extractives was similar in both pines with 38.5% in P. pinea and 37.7% in P. pin...

Barks of Tachigali guianensis and Tachigali glauca, from the Brazilian Amazon rainforest, were studied regarding anatomy and chemical composition. The barks were similar, with a narrow rhytidome, a ring of sclerified cells below the periderm, a widely dilated and sclerified nonconducting phloem, septate crystal strands, and extensive phenolic depos...

The chemical and anatomical properties of Eucalyptus globulus stumps barks collected from fresh stumps (SB) and from industrial stumps bark piles (ISB) were determined. The stump bark showed similar anatomical structure to that of the stem bark, however with abundant prismatic crystals in the axial parenchyma cells. Stumps barks (ISB) presented a g...

Residues of Cistus ladanifer obtained after commercial steam distillation for essential oil production were evaluated to produce cellulose enriched solids and added-value lignin-derived compounds. The delignification of extracted (CLRext) and extracted and hydrothermally pretreated biomass (CLRtreat) was studied using two organosolv processes, etha...

This study aimed to investigate the antioxidant ability and the chemical composition of apolar and polar extractives from Douglas-fir bark, cork and phloem, establishing a possible correlation with the structural variation along the tree stem and geographic location. Douglas-fir bark extractives' composition were analyzed at three stem heights in t...

The cutin content and composition of cork oak (Quercus suber) leaves was determined in six provenances with different seed geographical origin spreading across the species natural distribution. The cutin layer on the leaf surface was on average 518 μg/cm² of leaf area and represented 6.7% of the leaf dry weight, with no significant differences among...

Cork stopper granulates from five geographical origins from Portugal and six from Spain were analyzed regarding polyphenol composition by HPLC-DAD/ESI-MS and geographical discrimination studied by near-infrared spectroscopy (NIRS). The phenolic composition of the eleven origins ranged from 30 to 52 mg/g cork granulates, with vescavaloninic acid, ca...

This first dendrochronological study of 13 violins and cellos from Portuguese workshops of the XVIII and XIX centuries aims at a deeper knowledge of dates and origin of the top woods used to build the instruments, as well as adding to the understanding of specific assembly techniques. A similar study was also made on 10 violins and cellos of foreig...

Waste biomass composed of cork-rich and phloem-rich granules obtained from the fractioning of Quercus cerris L. bark were characterized for bulk density, chemical composition, bio-active components, ash composition, and higher heating value. Bulk density of the fractions relate to their cork content and deceases with smaller particle size due to a...

Three mature Eucalyptus globulus trees with 40 years of age were studied at three height levels (0%, 35%, and 60% of total tree height) and at three radial regions (sapwood, inner and outer heartwood). The composition of lipophilic extracts was evaluated and an extensive list of 202 compounds was reported for the first time. The fatty acids were th...

The chemical composition of cuticular waxes and pigments and the morphological features of cork oak (Quercus suber) leaves were determined for six samples with seeds of different geographical origins covering the natural distribution of the species. The leaves of all samples exhibited a hard texture and oval shape with a dark green colour on the ha...

The chemical composition and anatomy of the woody follicles of the hakea fruits are characterized here for the first time, aiming at an appraisal of their potential valorization. Hakea sericea Schrader is a woody shrub with evergreen needle-like leaves and fruits composed of woody follicles that surround the seed. The woody follicles have two dehis...

Pyrolysis kinetics of Quercus cerris cork was investigated using thermogravimetric analysis with heating rates of 10, 20, 50, and 100 °C min−1. The activation energies and chemical compositions of cork components were determined by different model-fitting methods, isoconversional Kissinger-Akahira-Sunose (KAS) method, and Lorentzian multi-peak fitt...

Purpose. Acetylcholinesterase (AChE) inhibitors are used to treat Alzheimer’s patients because they enhance cholinergic neurotransmission. It is urgent to find new and efficient inhibitors from natural sources, highly bioavailable with low or no toxicity. The plant kingdom is extremely rich in a variety of compounds that are potent AChE inhibitors:...

As duas pinturas, representando Santa Luzia e o Martírio de São Sebastião, feitas por Belchior de Matos (c. 1570-1628) para uma pequena ermida de Peniche, no início do século XVII, têm suportes de madeira que as primeiras observações, realizadas no âmbito de uma intervenção de conservação e restauro, sugeriram ter excelente qualidade e influências...

Changes in the lignin structure of eight eucalypt species (E. botryoides, E. globulus, E. grandis, E. maculata, E. propinqua, E. rudis, E. saligna, and E. viminalis) upon mild thermal treatment, where the temperature was gradually raised from 160 to 230 °C over 3 h, were studied by solid-state carbon nuclear magnetic resonance (¹³C NMR) and after l...

Cork is a world-renowned material used for sealing wine bottles. Cork is a cellular material with chemical inertia and a set of physical and mechanical properties that provide an outstanding performance for in-bottle wine aging, by combining minute oxygen transfer with sealing, durability, and chemical stability, for example, inertness toward the l...

Lignins from different tree barks, including Norway spruce (Picea abies), eucalyptus (Eucalyptus globulus), mimosa (Acacia dealbata) and blackwood acacia (A. melanoxylon), are thoroughly characterized. The lignin from E. globulus bark is found to be enriched in syringyl (S) units, with lower amounts of guaiacyl (G) and p‐hydroxyphenyl (H) units (H/...

Different biomass fractions of Cistus ladanifer and solid residues from essential oil distilleries were structurally and chemically evaluated. The C. ladanifer biomass fractions showed chemical differences mainly related to extractives (e.g., 10.8% and 53.7% in stems and leaves) and lignin (e.g., 21.2% and 15.4% in stems and leaves). The distillery...

Life Cycle Assessment has become one of the most recognized and internationally accepted method for examining the environmental performance of forest products and processes. The main aim of this study was to evaluate the potential environmental impact associated with different commercial outputs of maritime pine wood (round, industrial, and residua...

Climate change induces in the Mediterranean region more frequent and extreme events, namely, heat waves and droughts, disturbing forest species and affecting their productivity and product quality. The cork oak (Quercus suber) is present along the western Mediterranean basin and its outer bark (cork) is sustainably collected and used for several pr...

Bark residual side streams from industries (Eucalyptus globulus—Eg and Picea abies—Pa) or from control of invasive species in Mediterranean countries (Acacia melanoxylon—Am and Acacia dealbata—Ad) are burned for energy production, although their high content of extractable compounds points to a possible valorization as sources of phytochemicals wit...

Eucalyptus globulus (Eg) and Picea abies (Pa) residual barks from pulp and solid wood industries were studied regarding their fractionation. Extractive-free barks were treated through autohydrolysis (severity factors 3.3–4.7) to obtain non-cellulosic rich oligosaccharides/monosaccharides moieties, followed by enzymatic saccharification of the (most...

PurposeThe overall aim of this work is to evaluate bio-refinery potential of Enset fiber. The effect of non-catalyzed and alkali-catalyzed hydrothermal processes was investigated to fractionate Enset fiber bundle.Methods The treatments were made at 130 °C, 150 °C, 180 °C, and 200 °C and the composition of the solids regarding lignin and monomeric s...

The shells of three important food nuts, walnut, almond, and pine nut, were studied in view of valorization as residues. The shells differed chemically: walnut shells had 10.6% extractives, 30.1% lignin, and 49.7% polysaccharides; almond shells 5.7% extractives, 28.9% lignin, and 56.1% polysaccharides; and pine nut shells 4.5% extractives, 40.5% li...

[This corrects the article DOI: 10.1016/j.heliyon.2019.e02910.].

Sustainability of cork oak (Quercus suber) forests is threatened by biotic and abiotic factors and characterization of potentially differing genetic resources has therefore gained importance. This work addresses the chemical variation of the three tissues of cork oak stems – cork, phloem and wood – in relation to tree and provenance, looking for ge...

Optimization of the supercritical fluid extraction of Quercus cerris cork was carried out using Box-Behnken design of experiments and response surface methodology (RSM). The optimized process variables were temperature (T: 40, 50 and 60 °C), ethanol content (EtOH: 0.0, 2.5 and 5.0 wt%) and CO2 flow rate (QCO2: 5, 8 and 11 gmin-1). The studied respo...

The chapter exposes the performance of Acacia melanoxylon wood for pulping production, regarding yields and kappa number but also the pulp and paper properties. The use of spectroscopy techniques is also emphasized.

Spent olive pomace from the two-phase extraction system of virgin olive oil and olive pomace oil, is a major agro-industrial residue. Present study aimed at the valorization of residual olive pomace and stones (seeds) by hydrothermal treatment and enzymatic hydrolysis of glucans. Both residues contain lignin (31.2% and 42.1%), glucans (13.8% and 15...

This work encompasses a comparison of the extraction of Quercus cerris cork with methanol, ethanol, dichloromethane, and petroleum ether by Soxhlet and room temperature batch solid-liquid extraction (SLE) and with supercritical carbon dioxide modified with ethanol. The maximum total extraction yield (ηTotal) was attained by Soxhlet extraction with...

Introduction: Suberin, as part of plant protective barriers, is one of the most important natural polymers after cellulose and lignin. For a full elucidation of suberin structure the quantification of glycerol, fatty α,ω-diacids and ω-hydroxyacids, the major building blocks of suberin, is of primary importance. Glycerol is often lost in the most u...