Browsing by Subject "KRAFT LIGNIN"

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  • West, Mark A.; Hickson, Aynsley C.; Mattinen, Maija-Liisa; Lloyd-Jones, Gareth (2014)
    Lignin preparations from kraft and sulfite pulping, steam explosion, and enzyme saccharification processes were assessed as substrates for lignin polymerization catalyzed by Trametes hirsuta laccase (ThL). Oxygen consumption associated with laccase catalyzed oxidation of the selected lignins was measured using a microplate-based oxygen assay. Laccase-induced changes in the molecular masses of the lignin polymers were assessed with aqueous-alkaline size exclusion chromatography (SEC) and changes in monomeric phenolics by reverse-phase high pressure liquid chromatography (HPLC). Obtaining consistent results in the lignin-laccase assay system required careful pH monitoring and control. All lignin preparations were oxidized by ThL, the rate being highest for steam-exploded eucalypt and lowest for enzyme-saccharified lignin. Comparing lignins, higher lignin-laccase reactivity was correlated with lower lignin molecular mass and higher amounts of monomeric phenolics. Solubility was not an indicator of reactivity. Steam-exploded and lignosulfonate-treated pine preparations were further fractionated by ultrafiltration to determine what molecular mass fractions were the most reactive in ThL catalyzed oxidation. Both retentate (> 3kDa), and to a lesser degree permeate (<3kDa), fractions were reactive.
  • Zinovyev, Grigory; Sulaeva, Irina; Podzimek, Stepan; Roessner, Dierk; Kilpeläinen, Ilkka; Sumerskii, Ivan; Rosenau, Thomas; Potthast, Antje (2018)
    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 488nm, 633nm, 658nm, or 690nm, 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 785nm 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.
  • Figueiredo, Patricia; Lahtinen, Maarit; Agustin, Melissa; Morais de Carvalho, Danila; Hirvonen, Sami-Pekka; Penttilä, Paavo A.; Mikkonen, Kirsi S. (2021)
    The production of lignin nanoparticles (LNPs) has emerged as a way to overcome the highly variable and complex molecular structure of lignin. It can offer morphological control of the lignin polymer, allowing the formation of stable LNP dispersions in aqueous media, while increasing the potential of lignin for high-value applications. However, the polydispersity and morphology of LNPs varies depending on the lignin grade and preparation method, and a systematic comparison using different technical lignins is lacking. In this study, it was attempted to find a green fabrication method with a distinct solvent fractionation of lignin to prepare LNPs using three different technical lignins as starting polymers: BLN birch lignin (hardwood, BB), alkali Protobind 1000 (grass, PB), and kraft LignoBoost (softwood, LB). For that, three anti-solvent precipitation approaches to prepare LNPs were systematically compared: 70 % aqueous ethanol, acetone/water (3 : 1) and NaOH as the lignin solvent, and water/aqueous HCl as the anti-solvent. Among all these methods, the acetone/water (3 : 1) approach allowed production of homogeneous and monodisperse LNPs with a negative surface charge and also spherical and smooth surfaces. Overall, the results revealed that the acetone/water (3 : 1) method was the most effective approach tested to obtain homogenous, small, and spherical LNPs from the three technical lignins. These LNPs exhibited an improved stability at different ionic strengths and a wider pH range compared to the other preparation methods, which can greatly increase their application in many fields, such as pharmaceutical and food sciences.
  • Agustin, Melissa; Morais de Carvalho, Danila; Lahtinen, Maarit; Hilden, Kristiina; Lundell, Taina; Mikkonen, Kirsi S. (2021)
    Lignin is an abundant natural feedstock that offers great potential as a renewable substitute for fossil-based resources. Its polyaromatic structure and unique properties have attracted significant research efforts. The advantages of an enzymatic over chemical or thermal approach to construct or deconstruct lignins are that it operates in mild conditions, requires less energy, and usually uses non-toxic chemicals. Laccase is a widely investigated oxidative enzyme that can catalyze the polymerization and depolymerization of lignin. Its dual nature causes a challenge in controlling the overall direction of lignin-laccase catalysis. In this Review, the factors that affect laccase-catalyzed lignin polymerization were summarized, evaluated, and compared to identify key features that favor lignin polymerization. In addition, a critical assessment of the conditions that enable production of novel lignin hybrids via laccase-catalyzed grafting was presented. To assess the industrial relevance of laccase-assisted lignin valorization, patented applications were surveyed and industrial challenges and opportunities were analyzed. Finally, our perspective in realizing the full potential of laccase in building lignin-based materials for advanced applications was deduced from analysis of the limitations governing laccase-assisted lignin polymerization and grafting.
  • Agustin, Melissa; Penttilä, Paavo; Lahtinen, Maarit; Mikkonen, Kirsi S. (2019)
    The production of lignin nanoparticles (LNPs) has opened new routes to the utilization of lignin in advanced applications. The existing challenge, however, is to develop a production method that can easily be adapted on an industrial scale. In this study, we demonstrated a green and rapid method of preparing LNPs directly from a sulfur-free alkaline pulping liquor by combining acid precipitation and ultrasonication. The combined method produced spherical LNPs, with a hierarchical nanostructure and a highly negative surface charge, within only 5 min of sonication. The mild, rapid sonication was achieved by sonicating directly without prior drying of the acid-precipitated and dialyzed lignin. Optimization of the method revealed the potential for minimizing acid consumption, shortening the dialysis time, and processing directly the alkaline liquor with as much as 20 wt % lignin. The isolated LNPs were stable during storage for 180 days, at a pH range of 4–7, and in a dispersing medium below 0.1 M NaCl. The LNPs also displayed excellent emulsifying properties, stabilizing oil-in-water emulsions. Thus, this simple and energy-efficient method opens a sustainable, straightforward, and scalable route to the production of organic solvent-free LNPs, with high potential as interface stabilizers of multiphase systems in the food and medical industries.
  • Mikkonen, Kirsi S. (2020)
    Wood biomass is an abundant renewable source of materials, but due to the accelerating depletion of natural resources, it is important to explore new ways to use it in a more sustainable manner. Modern technologies enable the recovery and valorization of the main components of wood—namely, cellulose, lignin, and hemicelluloses—contributing to sustainability. However, the method of isolation and resulting structure and purity of lignocellulosic materials determine their functionality and applicability. This review discusses the properties of all three main wood-based compounds that can stabilize emulsions, a class of industrial dispersions that are widely used in life science applications and chemicals. Due to the multi-billion-dollar annual market for hydrocolloids, the food, pharmaceutical, cosmetic, coating, and paint industries are actively seeking new sustainable emulsion stabilizers that fulfill the demanding requirements regarding safety and functionality. Wood-derived stabilizers facilitate various mechanisms involved in emulsion stabilization: (1) development of amphiphilic structures that decrease interfacial tension, (2) stabilization of interfaces by particles according to the Pickering theory, and (3) increase in the viscosity of emulsions’ continuous phase. This review presents pathways for treating cellulose, lignin, and hemicelluloses to achieve efficient stabilization and provides suggestions for their broad use in emulsions.
  • Kowalczyk, Joanna; Peng, Mao; Pawlowski, Megan; Lipzen, Anna; Ng, Vivian; Singan, Vasanth; Wang, Mei; Grigoriev, Igor V.; Mäkelä, Miia (2019)
    Lignocellulosic plant biomass is an important feedstock for bio-based economy. In particular, it is an abundant renewable source of aromatic compounds, which are present as part of lignin, as side-groups of xylan and pectin, and in other forms, such as tannins. As filamentous fungi are the main organisms that modify and degrade lignocellulose, they have developed a versatile metabolism to convert the aromatic compounds that are toxic at relatively low concentrations to less toxic ones. During this process, fungi form metabolites some of which represent high-value platform chemicals or important chemical building blocks, such as benzoic, vanillic, and protocatechuic acid. Especially basidiomycete white-rot fungi with unique ability to degrade the recalcitrant lignin polymer are expected to perform highly efficient enzymatic conversions of aromatic compounds, thus having huge potential for biotechnological exploitation. However, the aromatic metabolism of basidiomycete fungi is poorly studied and knowledge on them is based on the combined results of studies in variety of species, leaving the overall picture in each organism unclear. Dichomitus squalens is an efficiently wood-degrading white-rot basidiomycete that produces a diverse set of extracellular enzymes targeted for lignocellulose degradation, including oxidative enzymes that act on lignin. Our recent study showed that several intra- and extracellular aromatic compounds were produced when D. squalens was cultivated on spruce wood, indicating also versatile aromatic metabolic abilities for this species. In order to provide the first molecular level systematic insight into the conversion of plant biomass derived aromatic compounds by basidiomycete fungi, we analyzed the transcriptomes of D. squalens when grown with 10 different lignocellulose-related aromatic monomers. Significant differences for example with respect to the expression of lignocellulose degradation related genes, but also putative genes encoding transporters and catabolic pathway genes were observed between the cultivations supplemented with the different aromatic compounds. The results demonstrate that the transcriptional response of D. squalens is highly dependent on the specific aromatic compounds present suggesting that instead of a common regulatory system, fine-tuned regulation is needed for aromatic metabolism.