Thermally assisted hydrolysis and alkylation of lignins in the presence of tetra-alkylammonium hydroxides

Three different milled lignins isolated from bamboo, pine and beech, corresponding to the three different structural groups, have been subjected to pyrolysis in the presence of tetramethylammonium hydroxide (TMAH) and tetrabutylammonium hydroxide (TBAH). Pyrolysis of the lignins in the presence of TMAH releases the methyl esters and methyl ethers of the different lignin monomers. Several moieties bearing carboxylic acid groups, not previously detected using pyrolytic techniques, could be released from the three lignins, suggesting that the presence of these moieties in the lignin structure have been underestimated.The authors wish to thank the CICyT (Spanish Direction General de Investigation Cientifica y Tecnica; Project PB91-0074) for financial support.Peer Reviewe

Phenylphenalenone type compounds from the leadf fibers of abaca (Musa textilis)

1Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, P.O. Box 1052, E-41080, Seville, Spain 2Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain 3Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán, 04510 México D. F., MéxicoA series of phenylphenalenone–type compounds, known to play a role as phytoalexins in plants of the Musaceae family, have been identified for the first time in the leaf fibers of abaca (Musa textilis). Among the phenylphenalenone-type compounds identified, the structure of a novel compound, (1R) -2,3-dihydro-4,9-dihydroxy-8-methoxy-1-phenylphenalene, has also been described in abaca fibers. Its structure was elucidated by analysis of 1D- and 2D-NMR (COSY, HSQC, HMBC) spectroscopic data.Financial support from the project AGL2005-01748.Peer reviewe

Chemical characterization of lignin and lipophilic fractions from leaf fibers of curaua (Ananas erectifolius)

E-mail: [email protected] (J.C. del Río)The chemical composition of leaf fibers of curaua (Ananas erectifolius), an herbaceous plant native of Amazonia, was studied. Special attention was paid to the content and composition of lignin and lipophilic compounds. The analysis of lignin in the curaua fibers was performed “in situ” by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and showed a lignin composition with a p-hydroxyphenyl:guaiacyl:syringyl units (H:G:S) molar proportion of 30:29:41 (S/G molar ratio of 1.4). The presence of p-hydroxycinnamic acids (p-coumaric and ferulic acids) in curaua fibers was revealed upon pyrolysis in the presence of tetramethylammonium hydroxide. On the other hand, the main lipophilic compounds, analysed by GC/MS, were series of long-chain n-fatty acids, n-fatty alcohols, α- and ω-hydroxyacids, monoglycerides, sterols and waxes. Other compounds, such as ω-hydroxy monoesters and ω-hydroxy acylesters of glycerol were also found in this fiber in high amounts.Peer reviewe

Oxidative modification of paper pulp lipophilic extractives by laccase-mediator system

Recently, we have shown the effectiveness of the laccase-mediator system in removing lipophilic extractives from pulp regardless the pulping process and the raw material used. This paper summarizes our research findings on the chemistry of the reactions of the main lipophilic extractives present in paper pulps with the laccase-mediator system. The results attained in reactions of several model lipids - including alkanes, fatty alcohols, fatty acids, resin acids, free sterols, sterol esters and triglycerides - with a fungal laccase in the presence of HBT as mediator, are discussed in the context of enzymatic control of pitch deposits, to explain the removal of complex lipid mixtures during laccase-mediator treatment of different pulp types, including eucalypt pulp.This study was funded by the BIORENEW EU-project (NMP2-CT-2006-026456) and the Spanish MICINN (AGL-2008-00709). Beldem (Andenne, Belgium) is acknowledged for laccase supply. S. Molina and J. Rencoret are acknowledged for their contribution to this work.Peer reviewe

Chemical composition of lipophilic extractives from non-woody plants used for manufacturing high-quality papers

The chemical composition of lipophilic extractives from fibers of three annual plants, namely hemp (Cannabis sativa), flax (Linum usitatissimum) and kenaf (Hibiscus cannabinus) that are commonly used for high quality paper pulp production was studied. The cloroform soluble fractions of the acetone extracts of the fibers were analyzed by gas chromatography-mass spectrometry. The main compounds identified were series of n-alkanes, n-fatty acids, n-aldehydes, n-fatty alcohols and waxes. On the other hand, free and esterified sterols and triterpenols, steroid hydrocarbons, steroid and triterpenoid ketones, as well as sterol glycosides were also found in the fibers studied here.A.G. acknowledges a "Ramón y Cajal" contract of the Spanish MCYT. We thank CELESA (Tortosa, Spain) for providing the raw materials.Peer reviewe

Chemical composition of lipophilic extractives from sisal (Agave sisalana) fibers

Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, PO Box 1052, E-41080 Seville, Spain. Corresponding author, E-mail: [email protected] (A. Gutiérrez)The chemical composition of lipophilic extractives from sisal (Agave sisalana) fibers, which are used for high-quality paper pulp production was studied. The lipophilic extract, which accounted for 0.5 % of total sisal fiber weight, was analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) using short- and medium-length high temperature capillary columns, respectively. For a more detailed characterization, the extract was fractionated by solid-phase extraction and the fractions obtained were analyzed by GC and GC/MS. The most predominant compounds identified were fatty acids (30% of total lipids) including α- and -hydroxyfatty acids, fatty alcohols (20%), free sterols (11%), alkanes (11%) and a series of ferulic acid esters of long chain alcohols and -hydroxyfatty acids (10%). Additionally, steroid hydrocarbons and ketones, monoglycerides, aldehydes, waxes, and sterol glycosides were also found together with minor amounts of diglycerides, and sterol esters.This study has been supported by the Spanish Ministerio de Ciencia y Tecnología (MCYT) (projects AGL2002-00393 and AGL2005-01748) and EU project (BIORENEW, NMP2-CT-2006-026456). We thank CELESA pulp mill (Tortosa, Spain) for providing the sisal fibers.Peer reviewe

Isolation and structural characterization of the acetylated heteroxylan from sisal (Agave sisalana) and its fate during alkaline pulping and TCF/ECF bleaching.

The heteroxylan from sisal, an O-acetyl-(4-O-methylglucurono)xylan with a molecular weight (Mw) of 18 kDa, was isolated by extraction of peracetic holocellulose with Me2SO and thoroughly characterized by wet chemistry, and NMR spectroscopy. The heteroxylan backbone is composed of (1→4)-linked β-D-xylopyranosyl units (Xylp) partially ramified with terminal (1→2)-linked 4-O-methyl-α-D-glucuronosyl (MeGlcpA) and a small proportion of α-D-glucuronosyl (GlcpA) residues. Roughly 61mol% of Xylp residues are acetylated (DS =0.70). During soda/AQ pulping, GlcpA and MeGlcA are partially removed or converted to 4-deoxy-β-L-threo-hex-4-enopyranosyluronic acid (HexA), though notable proportion of GlcpA maintained intact. The major part of acetyl groups was hydrolyzed during pulping. It was proposed that the predominantly low molecular weight xylan fraction was removed from pulp during bleaching. The profiles of uronosyl residues in xylans from TCF and ECF bleached sisal pulps were rather different.This study has been supported by the Spanish MEC (Project AGL2005-01748) and EU Contract NMP2-CT-2006-26456. We thank CELESA (Tortosa, Spain) for providing the samples. G.M. thanks the Spanish Ministry of Education for a FPI fellowship.Peer reviewe

Biomarkers in the bitominous fraction of a spanish brown coal

8 pages, 5 figures, 2 tables, 19 references.Molecular indicators such as diterpenoid and triterpenoid hydrocarbons and steroid alcohols and ketones have been identified in the bituminous fraction of the lignite from Arenas del Rey (AR), South Spain. Diterpenoid hydrocarbons consists mainly of kaurenes and are indicati ve of higher plant contributions, specially from conifer resins. Triterpenoids consist mainnly of 17beta(H),21beta{H)-hopanes derived from recent biogenic activity which indicates the geological immaturity of this lignite and implies that it has undergone only a mild thermal history. Sterols consist of cholesterol, carmpesterol, stigmasterol and beta-sitosterol and their distribution suggests a possible phytoplankton input, which should confirm the geological hypothesis that this sediment had an estuarine or deltaic origin. Occurrence of stanones with the biological 5alfa configuration was also observed.Peer reviewe

Towards industrially-feasible delignification and pitch removal by treating paper pulp with Myceliophthora thermophila laccase and a phenolic mediator

The ability of two natural phenols to act as mediators of the recombinant Myceliophthora thermophila laccase (MtL) in eucalypt-pulp delignification was investigated. After alkaline peroxide extraction, the properties of the enzymatically-treated pulps improved with respect to the control. The pulp brightness increased (3.1 points) after the enzymatic treatment with MtL alone, but the highest improvements were obtained after the MtL treatment using syringaldehyde (4.7 points) and especially methyl syringate (8.3 points) as mediators. Likewise, a decrease in kappa number up to 2.7 points was obtained after the MtL–methyl syringate treatment, followed by decreases of 1.4 and 0.9 points after the treatments with MtL–syringaldehyde and MtL alone, respectively. On the other hand, removal of the main lipophilic extractives present in eucalypt pulp was observed after the above laccase–mediator treatments. Finally, the doses of both MtL and methyl syringate were reduced, and results compatible with industrial implementation were obtained.This study was funded by the BIORENEW and LIGNODECO EU projects (NMP2-CT-2006-026456 and KBBE-2009-3-244362, respectively) and the ELLE and RAPERO Spanish MICINN (co-financed by FEDER funds) projects AGL2008-00709 and BIO2008-01533, respectively).Peer reviewe

Steroid hydroxylation by basidiomycete peroxygenases: A combined experimental and computational Study

13 páginas.-- 7 figuras.-- 4 tablas.-- 40 referencias.-- Supplemental material for this article may be found at http://dx.doi.org/10.1128/AEM.00660-15.The goal of this study is the selective oxyfunctionalization of steroids under mild and environmentally friendly conditions using fungal enzymes. With this purpose, peroxygenases from three basidiomycete species were tested for the hydroxylation of a variety of steroidal compounds, using H2O2 as the only cosubstrate. Two of them are wild-type enzymes from Agrocybe aegerita and Marasmius rotula, and the third one is a recombinant enzyme from Coprinopsis cinerea. The enzymatic reactions on free and esterified sterols, steroid hydrocarbons, and ketones were monitored by gas chromatography, and the products were identified by mass spectrometry. Hydroxylation at the side chain over the steroidal rings was preferred, with the 25-hydroxyderivativespredominating. Interestingly, antiviral and other biological activities of 25-hydroxycholesterol have been reported recently (M. Blanc et al., Immunity 38:106-118, 2013, http://dx.doi.org/10.1016/j.immuni.2012.11.004). However, hydroxylation in the ring moiety and terminal hydroxylation at the side chain also was observed in some steroids, the former favored by the absence of oxygenated groups at C-3 and by the presence of conjugated double bonds in the rings. To understand the yield and selectivity differences between the different steroids, a computational study was performed using Protein Energy Landscape Exploration (PELE) software for dynamic ligand diffusion. These simulations showed that the active-site geometry and hydrophobicity favors the entrance of the steroid side chain, while the entrance of the ring is energetically penalized. Also, a direct correlation between the conversion rate and the side chain entrance ratio could be established that explains the various reaction yields observed.This study was supported by the INDOX (KBBE-2013-7-613549), PEROXICATS (KBBE-2010-4-265397), and PELE (ERC-2009-Adg 25027) EU projects. We have no conflicts of interest to declare.Peer reviewe