| 1. |
- Holmgren, Anders, et al.
(author)
-
On the role of the monolignol gamma-carbon functionality in lignin biopolymerization
- 2009
-
In: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 70:1, s. 147-155
-
Journal article (peer-reviewed)abstract
- In order to investigate the importance of the monomeric gamma-carbon chemistry in lignin biopolymerization and structure, synthetic lignins (dehydrogenation polymers; DHP) were made from monomers with different degrees of oxidation at the gamma-carbon, i.e., carboxylic acid, aldehyde and alcohol. All monomers formed a polymeric material through enzymatic oxidation. The polymers displayed similar sizes by size exclusion chromatography analyses, but also exhibited some physical and chemical differences. The DHP made of coniferaldehyde had poorer solubility properties than the other DHPs, and through contact angle of water measurement on spin-coated surfaces of the polymeric materials, the DHPs made of coniferaldehyde and carboxylic ferulic acid exhibited higher hydrophobicity than the coniferyl alcohol DHP. A structural characterization with C-13 NMR revealed major differences between the coniferyl alcohol-based polymer and the coniferaldehyde/ferulic acid polymers, such as the predominance of aliphatic double bonds and the lack of certain benzylic structures in the latter cases. The biological role of the reduction at the gamma-carbon during monolignol biosynthesis with regard to lignin polymerization is discussed.
|
|
| 2. |
- Moser, Carl, 1987-, et al.
(author)
-
Specific surface area increase during cellulose nanofiber manufacturing related to energy input
- 2016
-
In: BioResources. - : North Carolina State University. - 1930-2126. ; 11:3, s. 7124-7132
-
Journal article (peer-reviewed)abstract
- Softwood fibers pretreated with a monocomponent endoglucanase were used to prepare a series of cellulose nanofiber qualities using a microfluidizer and 2 to 34 MWh ton-1 of energy input. The specific surface area was determined for the series using critical point drying and gas adsorption. Although the specific surface area reached a maximum of 430 m2 g-1 at 11 MWh ton-1, the nanofiber yield and transmittance continued to increase beyond this point, indicating that more energy is required to overcome possible friction caused by an interwoven nanofiber network unrelated to the specific surface area. A new method for estimating the surface area was investigated using xyloglucan adsorption in pure water. With this method it was possible to follow the disintegration past the point of maximum specific surface area. The technical significance of these findings is discussed.
|
|
| 3. |
- Moser, Carl, et al.
(author)
-
Toward Industrially Feasible Methods for Following the Process of Manufacturing Cellulose Nanofibers
- 2015
-
In: BioResources. - : BioResources. - 1930-2126. ; 10:2, s. 2360-2375
-
Journal article (peer-reviewed)abstract
- Nanocellulose is a recently developed form of cellulose that has the potential to be used in many different industries, ranging from food to high-performance applications. This material is commercially manufactured through the homogenization of chemical pulps, but the process is energy-consuming and is still an important subject for development. Simple, robust methods are required for the quality control and optimization of industrial nanocellulose production. In this study, a number of different methods, based on different principles of monitoring the manufacture of cellulose nanofibers were evaluated and compared for five different nanocellulose qualities, both for their resolution and robustness/ease. Methods based on microscopy, light scattering, centrifugation, and viscosity were examined and all appeared useful for observing the manufacturing process during its initial stage. However, only methods based on centrifugation, turbidity, and transmittance yielded reliable data for the entire manufacturing process. Of these methods, transmittance measurement may be the best candidate for routine use because the method is simple, rapid, and only requires spectrophotometer equipment.
|
|
| 4. |
- Zhao, Yadong, et al.
(author)
-
Cellulose Nanofibers from Softwood, Hardwood, and Tunicate : Preparation-Structure-Film Performance Interrelation
- 2017
-
In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:15, s. 13508-13519
-
Journal article (peer-reviewed)abstract
- This work reveals the structural variations of cellulose nanofibers (CNF) prepared from different cellulose sources, including softwood (Picea abies), hardwood (Eucalyptus grandis × E. urophylla), and tunicate (Ciona intestinalis), using different preparation processes and their correlations to the formation and performance of the films prepared from the CNF. Here, the CNF are prepared from wood chemical pulps and tunicate isolated cellulose by an identical homogenization treatment subsequent to either an enzymatic hydrolysis or a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation. They show a large structural diversity in terms of chemical, morphological, and crystalline structure. Among others, the tunicate CNF consist of purer cellulose and have a degree of polymerization higher than that of wood CNF. Introduction of surface charges via the TEMPO-mediated oxidation is found to have significant impacts on the structure, morphology, optical, mechanical, thermal, and hydrophobic properties of the prepared films. For example, the film density is closely related to the charge density of the used CNF, and the tensile stress of the films is correlated to the crystallinity index of the CNF. In turn, the CNF structure is determined by the cellulose sources and the preparation processes. This study provides useful information and knowledge for understanding the importance of the raw material for the quality of CNF for various types of applications.
|
|
| 5. |
- Zhu, Hongli, et al.
(author)
-
A novel nano cellulose preparation method and size fraction by cross flow ultra- filtration
- 2012
-
In: Current organic chemistry. - : Bentham Science Publishers Ltd.. - 1385-2728 .- 1875-5348. ; :16, s. 1871-1875
-
Journal article (peer-reviewed)abstract
- A novel energy-efficient method called nanopulping (patent pending) to produce nanocellulose from chemical pulp, and a novel cross-flow ultra-filtration method to separate nanofibrils fractions of different size were applied in this study. Pretreatment with endoglucanase or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation seems to enhance the nanopulping process. Results were evaluated with atomic force microscope and ultrafiltration. The nanopulping produced a relatively inhomogeneous material with larger particles/ fibers in addition to nanofibers. However, by ultrafiltration of the material it was possible to obtain more homogeneous material in different dimensions with methods industrially acceptable.
|
|
