Association behaviour of lignins and lignin model compounds studied by multidetector size-exclusion chromatography

Purification and Fractionation of Lignin via ALPHA: Liquid-Liquid Equilibrium for the Lignin-Acetic Acid-Water System

In order to effectively practice the Aqueous Lignin Purification with Hot Agents (ALPHA) process for lignin purification and fractionation, the temperatures and feed compositions where regions of liquid-liquid equilibrium (LLE) exist must be identified. To this end, pseudo-ternary phase diagrams for the lignin-acetic acid-water system were mapped out at 45-95 °C and various solvent: feed lignin mass ratios (S : F). For a given temperature, the accompanying SL (solid-liquid), SLL (solid-liquid-liquid), and one-phase regions were also located. For the first time, ALPHA using acetic acid (AcOH)-water solution was applied to a lignin recovered via the commercial LignoBoost process. In addition to determining tie-line compositions for the two regions of LLE that were discovered, the distribution of lignin and key impurities (the latter can negatively impact lignin performance for materials applications) between the two liquid phases was also measured. As a representative example, lignin isolated in the lignin-rich phase was reduced 7x in metals and 4x in polysaccharides by using ALPHA with a feed solvent composition of 50-55 % AcOH and an S : F of 6 : 1, with said lignin being obtained at a yield of 50-70 % of the feed lignin and having a molecular weight triple that of the feed.

Lignin as a bioactive polymer and heavy metal absorber- an overview

As a pulping and bio-refinery by-product with phenolic chemical structure, lignin indicated high potential as natural antioxidant activity, UV blocker, antibacterial and toxic material absorbent properties. Presence of phenolic hydroxyl groups in lignin structure plays the main role of its antioxidant activity. However, lignin antioxidant power can change depending on its other structural features and functional groups like ortho-methoxy groups, -OCH₃ groups, the α-CH₂ groups, the aliphatic carbonyl groups, and the size of π-conjugated systems. Lignin in mixture with synthetic polymers, improved their thermal stability. Lignin has high UV light absorbing potential in broad-spectrum (UVA, UVB). Adding 1-5% of lignin into hand cream indicated excellent range of sun protection factor (SPF) with more than 95% UV light absorption. Lignin also indicated strong UV light protection when applied in different transparent film and protect paint, oil, and varnish from UV degradation. Lignosulfonate and other modified lignin including chemically modification, nano-particles and lignin hydrogel indicated high potential as heavy metal absorber.

Revisiting the Molar Mass and Conformation of Derivatized Fractionated Softwood Kraft Lignin

The limited utilization of reliable tools and standards for determination of the softwood kraft lignin molar mass and the corresponding molecular conformation hampers elucidation of the structure-property relationships of lignin. At issue, conventional size exclusion chromatography (SEC) is unable to robustly measure the molar mass because of a lack of calibration standards with a similar structure to lignin. In the present work, the determination of the absolute molar mass of acetylated technical lignin was revisited utilizing SEC combined with multi-angle light scattering with a band pass filter to suppress the fluorescence. Fractionated lignin isolated using sequential techniques of solvent and membrane methods was used to enhance the clarity of light-scattering profiles by narrowing the molar mass distribution of lignin fractions. Further information on the molecular conformation of derivatized samples was studied utilizing a differential viscometer, and chemical structures were identified by NMR spectroscopy analysis. Through the help of fractionation, intrinsic viscosity values were determined for the different fractions as a function of molecular weight cut-off membranes. The derivatized acetone-soluble lignin was found to possess a lower molecular weight and an extremely compact structure relative to the derivatized acetone-insoluble fraction based on a significantly lower "α" value in the Mark-Houwink-Sakurada plot (0.15 acetone-soluble vs 0.33 acetone-insoluble). The differences in geometry were supported by the linkage analysis from NMR showing the acetone-soluble part containing fewer native linkages. In both of these examples, kraft lignin behaved like a solid sphere, limiting the ability to provide entanglements between molecular chains. From this standpoint, macroscopic properties of lignin are justified with this knowledge of a dense and extremely compact structure.

Molar mass determination of lignins and characterization of their polymeric structures by multi-detector gel permeation chromatography

Molar masses, Mark-Houwink-Sakurada (MHS) exponents, and refractive index increments (dn/dc) for three lignins were determined without derivatization by multi-detector gel permeation chromatography (GPC) in dimethylformamide (DMF) with 0.05 M lithium bromide (LiBr). The lack of effectiveness of fluorescence filters on molar mass determination by GPC-multi-angle laser light scattering (MALS) was confirmed for softwood kraft lignin (Indulin AT) and revealed for mixed hardwood organosolv lignin (Alcell) as well as soda straw/grass lignin (Protobind 1000). GPC with viscometry detection confirmed that these lignins were present as compact molecules. The MHS exponent α for Indulin AT and Alcell was in the order of 0.1. Additionally, the intrinsic viscosity of Protobind 1000 for a given molar mass was much lower than that of either Alcell or Indulin AT. This is the first report of dn/dc values for these three lignins in DMF with 0.05 M LiBr.

High-Throughput Analysis of Lignin by Agarose Gel Electrophoresis

A high-throughput agarose gel electrophoresis (AGE) analytical method has been developed to separate lignin fractions according to their molecular weight (M_w), charge, and shape. Operating conditions to effect separation of species have been evaluated along with imaging parameters. Kraft, soda (Protobind), and Organosolv lignins showed distinct differences in migration. Bands were cut, extracted, and cross-analyzed by gel permeation chromatography (GPC), ¹H NMR, and pyrolysis GC/MS to confirm their identity as lignin. The band intensity was correlated with lignin concentration by running serially diluted samples and imaging each lane to produce a precise calibration curve. The AGE technique was used to monitor and compare enzymatic, bacterial, chemical, and hydrothermal lignin digestions. Each method showed changes in lignin migration and band intensities over time. Low M_w species were seen in samples collected from the anode buffer tank. Though requiring further development, the AGE method can provide structural information about the lignin and is accessible to biological and chemistry laboratories.

Lignin-Based Micro- and Nanomaterials and their Composites in Biomedical Applications

Lignin, as the most abundant aromatic renewable biopolymer in nature, has long been regarded as waste and simply discarded from the pulp and paper industry. In recent years, with many breakthroughs in lignin chemistry, pretreatment, and processing techniques, a lot of the inherent bioactivities of lignin, including antioxidant activities, antimicrobial activities, biocompatibilities, optical properties, and metal-ion chelating and redox activities, have been discovered and this has opened a new field not only for lignin-based materials but also for biomaterials. In this Review, the biological activities of lignin and drug/gene delivery and bioimaging applications of various types of lignin-based material are summarized. In addition, the challenges and limitations of lignin-based materials encountered during the development of biomedical applications are also discussed.

Getting Closer to Absolute Molar Masses of Technical Lignins

Determination of molecular weight parameters of native and, in particular, technical lignins are based on size exclusion chromatography (SEC) approaches. However, no matter which approach is used, either conventional SEC with a refractive index detector and calibration with standards or multi-angle light scattering (MALS) detection at 488 nm, 633 nm, 658 nm, or 690 nm, all variants can be severely erroneous. The lack of calibration standards with high structural similarity to lignin impairs the quality of the molar masses determined by conventional SEC, and the typical fluorescence of (technical) lignins renders the corresponding MALS data rather questionable. Application of MALS detection at 785 nm by using an infrared laser largely overcomes those problems and allows for a reliable and reproducible determination of the molar mass distributions of all types of lignins, which has been demonstrated in this study for various and structurally different analytes, such as kraft lignins, milled-wood lignin, lignosulfonates, and biorefinery lignins. The topics of calibration, lignin fluorescence, and lignin UV absorption in connection with MALS detection are critically discussed in detail, and a reliable protocol is presented. Correction factors based on MALS measurements have been determined for commercially available calibration standards, such as pullulan and polystyrene sulfonate, so that now more reliable mass data can be obtained also if no MALS system is available and these conventional calibration standards have to be resorted to.

Fast Track to Molar-Mass Distributions of Technical Lignins

Technical lignins (waste products obtained from wood pulping or biorefinery processes) have so far required lengthy analysis procedures and different eluents for molar-mass analysis by gel permeation chromatography (GPC). This challenge has become more pressing recently since attempts to utilize lignins have increased, leading to skyrocketing numbers of samples to be analyzed. A new approach, which uses the eluent DMSO/LiBr (0.5 % w/v) and converts lignosulfonate salts into their acidic form before analysis, overcomes these limitations by enabling measurement of all kinds of lignins (kraft, organosolv, soda, lignosulfonates) in the same size-exclusion chromatography (SEC) system without the necessity of prior time-consuming derivatization steps. In combination with ultra-performance liquid chromatography (UPLC), analysis times are shortened to one tenth of classical lignin GPC. The new approach is presented, along with a comparison of GPC and UPLC methods and a critical discussion of the analytical parameters.

Determination of molecular weight distributions in native and pretreated wood

The analysis of native wood components by size-exclusion chromatography (SEC) is challenging. Isolation, derivatization and solubilization of wood polymers is required prior to the analysis. The present approach allowed the determination of molecular weight distributions of the carbohydrates and of lignin in native and processed woods, without preparative component isolation steps. For the first time a component selective SEC analysis of sawdust preparations was made possible by the combination of two selective derivatization methods, namely; ionic liquid assisted benzoylation of the carbohydrate fraction and acetobromination of the lignin in acetic acid media. These were optimized for wood samples. The developed method was thus used to examine changes in softwood samples after degradative mechanical and/or chemical treatments, such as ball milling, steam explosion, green liquor pulping, and chemical oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The methodology can also be applied to examine changes in molecular weight and lignin-carbohydrate linkages that occur during wood-based biorefinery operations, such as pretreatments, and enzymatic saccharification.

Preparation and characterization of Kraft lignin-based moisture-responsive films with reversible shape-change capability

Preparation of moisture-responsive Kraft lignin-based materials by electrospinning blends of Kraft lignin fractions with different physical properties is presented. The differences in thermal mobility between lignin fractions are shown to influence the degree of interfiber fusion occurring during oxidative thermostabilization of electrospun nonwoven fabrics, resulting in different material morphologies including submicrometer fibers, bonded nonwovens, porous films, and smooth films. The relative amount of different lignin fractions and degree of fiber flow and fiber fusion is shown to influence the tendency for the electrospun materials to be transformed into moisture-responsive materials capable of reversible changes in shape. Material characterization by scanning electron microscopy and atomic force microscopy as well characterization of the chemical and physical properties of Kraft lignin fractions by dynamic rheology, 1H and 13C NMR, and gel permeation chromatography combined with multiangle laser light scattering are presented. A proposed mechanism underlying moisture-responsiveness, shape change, and shape recovery is discussed based on the differences in chemical structure and physical properties of Kraft lignin fractions.

Accurate and reproducible determination of lignin molar mass by acetobromination

The accurate and reproducible determination of lignin molar mass by using size exclusion chromatography (SEC) is challenging. The lignin association effects, known to dominate underivatized lignins, have been thoroughly addressed by reaction with acetyl bromide in an excess of glacial acetic acid. The combination of a concerted acetylation with the introduction of bromine within the lignin alkyl side chains is thought to be responsible for the observed excellent solubilization characteristics acetobromination imparts to a variety of lignin samples. The proposed methodology was compared and contrasted to traditional lignin derivatization methods. In addition, side reactions that could possibly be induced under the acetobromination conditions were explored with native softwood (milled wood lignin, MWL) and technical (kraft) lignin. These efforts lend support toward the use of room temperature acetobromination being a facile, effective, and universal lignin derivatization medium proposed to be employed prior to SEC measurements.

Effect of lignin-derived and furan compounds found in lignocellulosic hydrolysates on biomethane production

Hydrolysates resulting from the lignocellulosic biomass pretreatment in bioethanol production may be used to produce biogas. Such hydrolysates are rich in xylose but also contain lignin polymers or oligomers as well as phenolic and furan compounds, such as syringaldehyde, vanillin, HMF, furfural. The aim of this study was to investigate the impact of these byproducts on biomethane production from xylose. The anaerobic digestion of the byproducts alone was also investigated. No inhibition of the anaerobic digestion of xylose was observed and methane was obtained from furans: 430 mL CH(4)/g of furfural and 450 mL CH(4)/g of HMF; from phenolic compounds: 453 mL CH(4)/g of syringaldehyde and 105 mL CH(4)/g of vanillin; and, to a lesser extent, from lignin polymers: from 14 to 46 mL CH(4)/g MV. The use of different natural polymers (lignosulfonates, organosolv and kraft lignins) and synthetic dehydrogenative polymers showed that higher S/G ratios and lower molecular weights in lignin polymers led to greater methane production.

Natural Polymer Resources: Isolation, Separation and Characterization

This chapter describes various strategies and analytical techniques used for isolation, separation and characterization of natural polymers as the essential first step for their applications in food, feed and non-food products. It discusses different methods used for isolation and characterization of polysaccharides at the molecular and supramolecular levels. The discussion is exemplified by the detailed structural analysis of, among others, heteropolysaccharides like mucilage and fructans by permethylation, reductive cleavage and acetylation, followed by gas liquid chromatography. Data are also presented for supramolecular dimensions and molecular weights of poly-saccharides from various sources by different chromatographic methods combined with inline multiple detection systems (mass, light scattering, viscosity, fluorescence). The analysis and characterisation of plant and animal proteins are also briefly discussed.

CCoAOMT suppression modifies lignin composition in Pinus radiata

A cDNA clone encoding the lignin-related enzyme caffeoyl CoA 3-O-methyltransferase (CCoAOMT) was isolated from a Pinus radiata cDNA library derived from differentiating xylem. Suppression of PrCCoAOMT expression in P. radiata tracheary element cultures affected lignin content and composition, resulting in a lignin polymer containing p-hydroxyphenyl (H), catechyl (C) and guaiacyl (G) units. Acetyl bromide-soluble lignin assays revealed reductions in lignin content of up to 20% in PrCCoAOMT-deficient transgenic lines. Pyrolysis-GC/MS and 2D-NMR studies demonstrated that these reductions were due to depletion of G-type lignin. Correspondingly, the proportion of H-type lignin in PrCCoAOMT-deficient transgenic lines increased, resulting in up to a 10-fold increase in the H/G ratio relative to untransformed controls. 2D-NMR spectra revealed that PrCCoAOMT suppression resulted in formation of benzodioxanes in the lignin polymer. This suggested that phenylpropanoids with an ortho-diphenyl structure such as caffeyl alcohol are involved in lignin polymerization. To test this hypothesis, synthetic lignins containing methyl caffeate or caffeyl alcohol were generated and analyzed by 2D-NMR. Comparison of the 2D-NMR spectra from PrCCoAOMT-RNAi lines and synthetic lignins identified caffeyl alcohol as the new lignin constituent in PrCCoAOMT-deficient lines. The incorporation of caffeyl alcohol into lignin created a polymer containing catechyl units, a lignin type that has not been previously identified in recombinant lignin studies. This finding is consistent with the theory that lignin polymerization is based on a radical coupling process that is determined solely by chemical processes.

1-[3-Meth-oxy-4-(prop-2-yn-1-yl-oxy)phen-yl]ethanone

In the title compound, C(12)H(12)O(3), the meth-oxy and prop-2-yn-yloxy groups are nearly coplanar with the attached benzene ring [C-O-C-C torsion angles = 1.2 (3) and 2.2 (3)°, respectively]. In the crystal, inversion dimers linked by pairs of C-H⋯O inter-actions occur.

Propensity of lignin to associate: light scattering photometry study with native lignins

Many studies of lignins in solution invoke association and aggregation phenomena to explain their solution behavior (e.g., reprecipitation onto pulp fibers, condensation, etc.). Following their colloidal (apparent) molecular weights in solution as a function of time allows us to explore observable dissociation phenomena. These measurements were carried out using multiple angle laser light scattering (MALLS) photometry in the static mode. The challenges and opportunities of measuring the specific refractive index increment (dn/dC) of lignin solutions and determining the kinetics of the dissociation process were thus investigated. Hardwood and softwood representative lignins were isolated, and method for their full dissolution in THF was further developed, which then lead to accurate dn/dC values being obtained as a function of time. When coupled to additional work using light scattering static measurements and Zimm plots for the same solutions, this effort offers insight into the aggregation and ensuing dissociative events that operate within the lignin macromolecules.

2,2-Dibromo-1-(4-hydroxy-3-methoxyphenyl)ethanone

The mol­ecule of the title compound, C₉H₈Br₂O₃, is stabilized by an intra­molecular O—H⋯O inter­action. Inter­molecular C—H⋯O inter­actions connect mol­ecules into a two-dimensional array in the bc plane; connections between these are afforded by π–π stacking inter­actions [centroid–centroid distance 3.596 (5) Å].

On the propensity of lignin to associate: a size exclusion chromatography study with lignin derivatives isolated from different plant species

Despite evidence that lignin associates under both aqueous and organic media, the magnitude and nature of the underlying driving forces are still a matter of discussion. The present paper addresses this issue by examining both solution properties and size exclusion behaviour of lignins isolated from five different species of softwoods, as well as from the angiosperms Eucalyptus globulus and wheat straw. This investigation has used the recently described protocol for isolating enzymatic mild acidolysis lignin (EMAL), which offers lignin samples highly representative of the overall lignin present in the wood cell wall. The molecular weight distributions of these EMALs were found to be dependent upon the wood species from which they were isolated and upon the incubation conditions used prior to size exclusion chromatography. While the chromatograms of EMALs isolated from softwoods displayed a bimodal behaviour, the elution profiles of EMAL from E. globulus and straw were nearly unimodal. A marked tendency to dissociate prevailed under incubation at room temperature for all examined species with the exception of the straw lignin preparation; furthermore, lignin solutions incubated at 4 degrees C showed an associative behaviour manifested by an increase in the weight and number average molecular weights for some species. The extent of such association/dissociation, as well as the time needed for the process to reach completion, was also found to depend upon the wood species, i.e. lignins from softwoods were found to associate/dissociate to a greater extent than lignins from E. globulus and straw. The origin of such effects within the lignin structure is also discussed.

Effect of reaction media concentration on the solubility and the chemical structure of lignin model compounds

In plant cell walls, lignin polymerization occurs in concentrated polysaccharide gel. The effect of high polysaccharide concentrations on the structure of lignin-like polymers (DHPs=dehydrogenation polymers), were investigated by running lignification-like polymerization under three reaction conditions in which the concentrations of all reactants (xylan/coniferyl alcohol (CA)/oxidising system) were gradually increased. Control experiments were also run in similar conditions but without polysaccharides. DHPs showed increased solubility with increased concentrations of reactants in the presence of xylans but were mostly insoluble in buffer control experiments. The structures of DHPs were characterized by thioacidolysis and size exclusion chromatography (SEC). Results indicated that the frequency of beta-alkyl aryl ether bonds and DHP molecular weight increased with increasing concentration of the reaction mixture in the presence of xylans whereas those of control DHPs decreased slightly under the same conditions. This emphasizes the role of the pre-existing polysaccharide gel and high concentrations existing in the cell wall during construction of the lignin polymer.

Studies of xylan interactions and cross-linking to synthetic lignins formed by bulk and end-wise polymerization: a model study of lignin carbohydrate complex formation

The mechanism of lignin carbohydrate complex formation by addition of polysaccharides on quinone methide (QM) generated during lignin polymerisation was investigated using a model approach. Dehydrogenation polymers (DHPs, lignin model compounds) were synthesized from coniferyl alcohol in the presence of a glucuronoarabinoxylan (GAX) extracted from oat spelts, by Zutropfverfahren (ZT) and Zulaufverfahren (ZL) methods. The methods ZT and ZL differed in their distribution of QM over the reaction period but generated roughly the same QM amount. Steric exclusion chromatography of the ZT and ZL reaction products showed that only the ZT reaction produced high molar mass compounds. Covalent linkages in the ZT reaction involving ether bonds between GAX moiety and alpha carbon of the lignin monomer were confirmed by (13)C NMR and xylanase-based fractionation. The underlying phenomena were further investigated by examining the interactions between GAX and DHP in sorption experiments. GAX and DHPs were shown to interact to form hydrophobic aggregates. In the ZT process, slow addition permitted polymer reorganisation which led to dehydration around the lignin-like growing chains thereby limiting the addition of water on the quinone methide formed during polymerisation and thus favoured lignin-carbohydrate complex (LCC) formation.

Characterization of Arabinoxylan−Dehydrogenation Polymer (Synthetic Lignin Polymer) Nanoparticles

Coniferyl alcohol (G monomer) and a mixture of coniferyl alcohol/sinapyl alcohol (GS monomers, 1/1 ratio) were polymerized to dehydrogenation polymers (DHPs) in presence of two structurally related heteroxylans (HX) differing only in their phenolic substitution patterns. One (HX-40) was enriched in ferulate (FA) while the other (HX-90) was almost devoid of FA. The morphology of the resulting nanoparticles was studied by transmission electron microscopy whereas formation of particles was followed by size exclusion chromatography with online multiangle laser light scattering. HX-40-DHP-G- and HX-40-DHP-GS-derived particles display complex morphological patterns whereas HX-90-DHP-G and HX-90-DHP-GS present rather spherical shapes. The determination of particle sizes and molar masses showed that HX-90 samples formed denser particles than HX-40 ones. These differences are discussed in relation to the ferulate substitution level.

Characterization of Klason lignins by reversed-phase high-performance liquid chromatography using wide-pore octadecylsilica and stepwise gradients of dimethylformamide in water

RP-HPLC using stepwise gradients of N,N-dimethylformamide (DMF) in a phosphate-buffered (pH 3.00) aqueous mobile phase and a wide-pore (30 nm) octadecylsilica column has been applied to the analysis of a variety of lignins--organocell lignin, dioxane lignin, Björkman lignin, and Klason lignins from both softwoods and hardwoods, respectively, in order to demonstrate the usefulness of the approach for their characterization. Tandem combination of spectrophotometric diode array detection and fluorimetric detection was used to acquire more detailed information about the chromatographic behavior of lignins. The results show that a ten-step gradient can reveal distinct features of lignins and humic substances. Combination of good solvating properties of DMF for lignins together with a wide-pore RP sorbent improves surface interactions of the analytes and suppresses the influence of size exclusion effects. Thus it provides reproducibility of characterization profiles and robustness of the method. The calculated repeatability of the retention time of selected peaks was +/- 0.46% RSD. The reproducibility of the data within one week (set of seven data) was +/- 1.1% RSD. These data are also representative of the other well-shaped peaks of analyzed substances.

Determination of lignin by size exclusion chromatography using multi angle laser light scattering

A method was developed using high-performance size exclusion liquid chromatography (HPSEC) with multi-angle laser light scattering (MALLS), quasi-elastic light scattering (QELS), interferometric refractometry (RI) and UV detection to characterize and monitor lignin. The combination proved very effective at tracking changes in molecular conformation of lignin molecules over time; i.e. changes in molecular weight distribution, radius of gyration, and hydrodynamic radius. Until this study, UV detection (280 nm) had been the primary lignin determination method for chromatography. Three different HPLC columns were used to study the effects of pH, flow conditions, and mobile phase compositions (dimethyl sulphoxide, water, 0.1M NaOH, and lithium bromide) on the chromatography of lignin. Since light scattering accuracy is highly dependent on solute concentration, both the UV and RI detectors were calibrated for use as concentration detectors. Shodex Asahipak GS-320 HQ column with 0.1M NaOH (pH 12.0) run at 0.5 ml/min was found to give the highest separation and most consistent recovery. The study also revealed that the lignin aggregated at pH below 8.5. This aggregation was detected only by MALLS and was not observed on UV or RI detectors. It is very important to take this loss in apparent concentration due to aggregation into consideration before collecting reliable depolymerization data.

Chemical synthesis of beta-O-4 type artificial lignin

An artificial lignin polymer containing only the beta-O-4 substructure was synthesized. The procedure consists of two key steps: 1) polycondensation of a brominated monomer by aromatic Williamson reaction; and 2) subsequent reduction of the carbonyl polymer. 13C-NMR and HMQC spectra of the polymer were consistent with beta-O-4 substructures in milled wood lignin isolated from Japanese fir wood. The weight average degree of polymerization (DP(w)) ranged from 19.5 to 30.6, which is comparable to enzymatically synthesized artificial lignin from p-hydroxycinnamyl alcohols (dehydrogenation polymer, DHP) and some isolated lignins. Using this new lignin model polymer, it will now be possible to reinvestigate the properties and reactivity of the main lignin structure in terms of its polymeric character.

Size-exclusion chromatography of technical lignins in dimethyl sulfoxide/water and dimethylacetamide

Well defined spent sulfite liquor samples and lignosulfonate fractions obtained by ultrafiltration were analyzed using size-exclusion chromatography. Two different eluent systems (dimethyl sulfoxide/water/lithium bromide; dimethylacetamide/lithium chloride) were compared regarding their suitability for lignin analysis. The differences of the elution profiles and calculated molar masses were discussed using conventional and universal calibration. For further validation four technical lignins from a Round Robin test were included into the study. The results indicated that both analytical systems under investigation were well suited for the analysis of technical lignins.

Purification of Xylitol from Fermented Hemicellulosic Hydrolyzate Using Liquid–Liquid Extraction and Precipitation Techniques

Xylitol was produced by Candida guilliermondii by fermentation of sugarcane bagasse hemicellulosic hydrolysate. Undesirable impurities were extracted from the broth using either ethyl acetate, chloroform or dichloromethane. The best results on clarification of the broth without xylitol loss were obtained with ethyl acetate. When ethanol, acetone or tetrahydrofuran were used for precipitation of impurities, only tetrahydrofuran clarified the fermented broth, but a high xylitol loss (approximately 30%) was observed.