Fungal Treatment for the Valorization of Technical Soda Lignin.

Technical lignins produced as a by-product in biorefinery processes represent a potential source of renewable carbon. In consideration of the possibilities of the industrial transformation of this substrate into various valuable bio-based molecules, the biological deconstruction of a technical soda lignin by filamentous fungi was investigated. The ability of three basidiomycetes (Polyporus brumalis, Pycnoporus sanguineus and Leiotrametes menziesii) to modify this material, the resultant structural and chemical changes, and the secreted proteins during growth on this substrate were investigated. The three fungi could grow on the technical lignin alone, and the growth rate increased when the media were supplemented with glucose or maltose. The proteomic analysis of the culture supernatants after three days of growth revealed the secretion of numerous Carbohydrate-Active Enzymes (CAZymes). The secretomic profiles varied widely between the strains and the presence of technical lignin alone triggered the early secretion of many lignin-acting oxidoreductases. The secretomes were notably rich in glycoside hydrolases and H2O2-producing auxiliary activity enzymes with copper radical oxidases being induced on lignin for all strains. The lignin treatment by fungi modified both the soluble and insoluble lignin fractions. A significant decrease in the amount of soluble higher molar mass compounds was observed in the case of P. sanguineus. This strain was also responsible for the modification of the lower molar mass compounds of the lignin insoluble fraction and a 40% decrease in the thioacidolysis yield. The similarity in the activities of P. sanguineus and P. brumalis in modifying the functional groups of the technical lignin were observed, the results suggest that the lignin has undergone structural changes, or at least changes in its composition, and pave the route for the utilization of filamentous fungi to functionalize technical lignins and produce the enzymes of interest for biorefinery applications.

Rheology and microstructure of gels based on wheat arabinoxylans enzymatically modified in arabinose to xylose ratio.

BACKGROUND: Arabinoxylans (AX) are polysaccharides consisting of a backbone of xyloses with arabinose substituents ester-linked to ferulic acid (FA). The arabinose to xylose ratio (A/X) in AX may vary from 0.3 to 1.1. AX form covalent gels by cross-linking of FA but physical interactions between AX chains also contribute to the network formation. The present study aimed to investigate the rheological and microstructural characteristics of gels based on AX enzymatically modified in A/X. RESULTS: Tailored AX presented A/X ranging from 0.68 to 0.51 and formed covalent gels. Dimers of FA content and elasticity (G') increased from 0.31 to 0.39 g kg-1 AX and from 106 to 164 Pa when the A/X in the polysaccharide decreased from 0.68 to 0.51. Atomic force microscopy images of AX gels showed a sponge-like microstructure at A/X = 0.68, whereas, at lower values, gels presented a more compact microstructure. Scanning electron microscopy analysis of AX gels show an arrangement of different morphology, passing from an imperfect honeycomb (A/X = 0.68) to a flake-like microstructure (A/X = 0.51). CONCLUSION: Lower A/X values favor the aggregation of AX chains resulting in an increase in di-FA content, which improves the rheological and microstructural characteristics of the gel formed. © 2017 Society of Chemical Industry.

Essential oils and distilled straws of lavender and lavandin: a review of current use and potential application in white biotechnology.

The Lavandula genus, which includes lavender (Lavandula angustifolia) and lavandin (L. angustifolia × Lavandula latifolia), is cultivated worldwide for its essential oils, which find applications in perfumes, cosmetics, food processing and, more recently, in aromatherapy products. The chemical composition of lavender and lavandin essential oils, usually produced by steam distillation from the flowering stems, is characterized by the presence of terpenes (e.g. linalool and linalyl acetate) and terpenoids (e.g. 1,8-cineole), which are mainly responsible for their characteristic flavour and their biological and therapeutic properties. Lavender and lavandin distilled straws, the by-products of oil extraction, were traditionally used for soil replenishment or converted to a fuel source. They are mineral- and carbon-rich plant residues and, therefore, a cheap, readily available source of valuable substances of industrial interest, especially aroma and antioxidants (e.g. terpenoids, lactones and phenolic compounds including coumarin, herniarin, α-bisabolol, rosmarinic and chlorogenic acids). Accordingly, recent studies have emphasized the possible uses of lavender and lavandin straws in fermentative or enzymatic processes involving various microorganisms, especially filamentous fungi, for the production of antimicrobials, antioxidants and other bioproducts with pharmaceutical and cosmetic activities, opening up new challenging perspectives in white biotechnology applications.

A novel glucose dehydrogenase from the white-rot fungus Pycnoporus cinnabarinus: production in Aspergillus niger and physicochemical characterization of the recombinant enzyme.

Data on glucose dehydrogenases (GDHs) are scarce and availability of these enzymes for application purposes is limited. This paper describes a new GDH from the fungus Pycnoporus cinnabarinus CIRM BRFM 137 that is the first reported GDH from a white-rot fungus belonging to the Basidiomycota. The enzyme was recombinantly produced in Aspergillus niger, a well-known fungal host producing an array of homologous or heterologous enzymes for industrial applications. The full-length gene that encodes GDH from P. cinnabarinus (PcGDH) consists of 2,425 bp and codes for a deduced protein of 620 amino acids with a calculated molecular mass of 62.5 kDa. The corresponding complementary DNA was cloned and placed under the control of the strong and constitutive glyceraldehyde-3-phosphate dehydrogenase promoter. The signal peptide of the glucoamylase prepro sequence of A. niger was used to target PcGDH secretion into the culture medium, achieving a yield of 640 mg L(-1), which is tenfold higher than any other reported value. The recombinant PcGDH was purified twofold to homogeneity in a one-step procedure with a 41 % recovery using a Ni Sepharose column. The identity of the recombinant protein was further confirmed by immunodetection using western blot analysis and N-terminal sequencing. The molecular mass of the native PcGDH was 130 kDa, suggesting a homodimeric form. Optimal pH and temperature were found to be similar (5.5 and 60 °C, respectively) to those determined for the previously characterized GDH, i.e., from Glomerella cingulata. However PcGDH exhibits a lower catalytic efficiency of 67 M(-1) s(-1) toward glucose. This substrate is by far the preferred substrate, which constitutes an advantage over other sugar oxidases in the case of blood glucose monitoring. The substrate-binding domain of PcGDH turns out to be conserved as compared to other glucose-methanol-choline (GMCs) oxidoreductases. In addition, the ability of PcGDH to reduce oxidized quinones or radical intermediates was clearly demonstrated, which raises prospects for applying this enzyme to detoxify toxic compounds formed during the degradation of lignin.

Compositional analysis of Chinese water chestnut (Eleocharis dulcis) cell-wall material from parenchyma, epidermis, and subepidermal tissues.

Chinese water chestnut (Eleocharis dulcis (Burman f.) Trin ex Henschel) is a corm consumed globally in Oriental-style cuisine. The corm consists of three main tissues, the epidermis, subepidermis, and parenchyma; the cell walls of which were analyzed for sugar, phenolic, and lignin content. Sugar content, measured by gas chromatography, was higher in the parenchyma cell walls (931 µg/mg) than in the subepidermis (775 µg/mg) or epidermis (685 µg/mg). The alkali-extractable phenolic content, measured by high-performance liquid chromatography, was greater in the epidermal (32.4 µg/mg) and subepidermal cell walls (21.7 µg/mg) than in the cell walls of the parenchyma (12.3 µg/mg). The proportion of diferulic acids was higher in the parenchyma. The Klason lignin content of epidermal and subepidermal cell walls was ~15%. Methylation analysis of Chinese water chestnut cell-wall polysaccharides identified xyloglucan as the predominant hemicellulose in the parenchyma for the first time, and also a significant pectin component, similar to other nongraminaceous monocots.

In vitro protective effects of two extracts from bergamot peels on human endothelial cells exposed to tumor necrosis factor-alpha (TNF-alpha).

Bergamot ( Citrus bergamia Risso) is a less commercialized Citrus fruit, mainly used for its essential oil extracted from the peel. Bergamot peel (BP) represents about 60% of the processed fruits and is regarded as primary waste. However, it contains good amounts of useful compounds, such as pectins and flavonoids. Many of the bioactivities of Citrus flavonoids appear to impact vascular endothelial cells. Herein, we report the protective effect of two flavonoid-rich extracts from BP (endowed with radical-scavenging properties and lacking genotoxic activity) against alterations in cell modifications induced by the pleiotropic inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) on human umbilical vein endothelial cells (HUVECs), as demonstrated by monitoring intracellular levels of malondialdehyde/4-hydroxynonenal, reduced and oxidized glutathione and superoxide dismutase activity, and the activation status of nuclear factor-kappaB (NF-kappaB). Thus, BP appears to be a potential source of natural antioxidant/anti-inflammatory phytocomplexes to be employed as ingredients of nutraceutical products or functional foods.

Anatomical, chemical, and biochemical characterization of cladodes from prickly pear [Opuntia ficus-indica (L.) Mill.].

Opuntia ficus-indica cladodes represent the green stem of the plant and are generally used as animal feed or disposed of in landfills. The present work investigated the anatomical and chemical composition of Opuntia cladodes, which form the basis of their pharmacological effects. Glucose and galacturonic acid were the main sugars of Opuntia cladodes, whereas high-performance liquid chromatography (HPLC) analysis showed the presence of mainly kaempherol and isorhamnetin glycosides (glucoside and rhamnoside). The presence of high amounts of calcium oxalate crystals was demonstrated by light microscopy on fresh and lyophilized cladodes. No antimicrobial activity was observed even after enzymatic treatment. O. ficus-indica cladodes may retain material tightly associated with cell-wall components, and this property will have the potential to greatly reduce the bioavailability of bioactive compounds.

Enzymatic hydrolysis of flavonoids and pectic oligosaccharides from bergamot (Citrus bergamia Risso) peel.

Pectinolytic and cellulolytic enzymes (Pectinase 62L, Pectinase 690L, and Cellulase CO13P) were used to evaluate the solubilization of carbohydrates and low molecular weight flavonoids from bergamot peel, a major byproduct of the essential oil industry. The enzymes were characterized for main-chain and side-chain polysaccharide hydrolyzing activities and also against pure samples of various flavonoids previously identified in bergamot peel to determine various glycosidase activities. The addition of Pectinase 62L or 690L alone, or the combination of Pectinase 62L and Cellulase CO13P, was capable of solubilizing between 70 and 80% of the bergamot peel, and up to 90% of the flavonoid glycosides present were cleaved to their aglycones. Cellulase CO13P alone solubilized 62% of the peel but had no deglycosylating effect on the flavonoid glycosides. Over a 24-h time course, a rapid release of cell wall carbohydrates was observed after treatment with Pectinase 62L, with a concurrent gradual hydrolysis of the flavonoid glycosides. Size-exclusion chromatography of the solubilized extract showed that after 24-h incubation, the majority of the solubilized carbohydrates were present as monosaccharides with a smaller proportion of oligosaccharides.

Characterization of flavonoids and pectins from bergamot (Citrus bergamia Risso) peel, a major byproduct of essential oil extraction.

Bergamot peel is an underutilized byproduct of the essential oil and juice-processing industry. As with other Citrus peels, it still contains exploitable components, such as pectins and flavonoids. Commercial glycoside hydrolases, specifically a combination of pectolytic and cellulolytic enzymes, solubilized a high percentage of the material (81.94%). The flavonoid profile of the peel consisted of characteristic Citrus species flavanone rutinosides and neohesperosides derived from naringenin, eriodictyol, and hesperetin. In addition, a number of minor flavanone and flavone glycosides, not found in orange and lemon peels, were identified. The majority of flavonoids were extracted in the two 70% v/v EtOH extractions. Processing this material clearly has economic potential leading to low environmental impact.