Lignin constituents

Cresols are an excretory product of mammals and an intermediate biotransformation product of natural aromatics such as lignin constituents (Fiege and Bayer 1987). Consequently, soil microorganisms are capable of metabolizing cresols, and any anthropogenic release of cresol, other than massive spills, is likely to be rapidly degraded in soil (Section 5.3.2.3). 

Buxton DR, Russell JR. 1988. Lignin constituents and cell wall digestibility of grass and legume stems. Crop Sci 28 553-558. 

The purification procedure can be modified by omitting the last addition of chloroform (Lundquist and Kirk 1980). This results in a somewhat less efficient removal of carbohydrates but separation of the organic layer is easier. The precipitation in ether included in the preferred method removes residual extractives and other contaminants but also causes losses of ether-soluble lignin constituents. Purification procedures involving gel permeation chromatography (Kirk and Lundquist 1970, Bardet et al. 1985) should be considered when there is an interest in retaining the latter type of materials. Ether solubles from a preparation of spruce MWL have been examined (Lundquist et al. 1977). Hydrophilic constituents of dioxane-water extracts from milled spruce wood have recently been investigated (Lundquist et al. 1990). 

Martensson, O., and G. Karlsson. 1969. P-electron spin densities of lignin constituents. 

Lignin is an abundant component of vascular plants, and the phenolic units from which it is synthesized are relatively stable towards chemical alteration but exhibit some compositional variation with plant type. Lignin constituents are, therefore, potentially useful indicators of different types of vascular plant sources. Alkaline oxidation of lignins from vascular plant tissue using copper(II) oxide (e.g. Hedges Mann 1979 Hedges Ertel 1982) yields four groups of... 

The lignin constituent can be utilized to bond agrowaste fibers in fiberboard production without a further need for synthetic glues, as Quintana et al. [25] produced fiberboards from banana bunch fibers without use of any binders. The performed a thermomechanical pretreatment hydrolyzing many of the hemicelluloses and redistribute the hgnin polymer to expose it in the surface of the fiber. 

Chemical Constituents of Cell Wall. Variation in chemical composition across the cell wall is also shown in Figure 6. The principal constituents of cellulose, hemicellulose, and lignin are present throughout the cell wall but in different proportions. Cellulose is not present in the interfiber middle lamella, which is virtually all lignin. The layer is essentially all carbohydrates (qv), especially hemiceUuloses, having Uttie or no lignin. 

Cellulose is the most abundant of naturally occurring organic compounds for, as the chief constituent of the eell walls of higher plants, it comprises at least one-third of the vegetable matter of the world. The cellulose eontent of such vegetable matter varies from plant to plant. For example, oven-dried cotton contains about 90% cellulose, while an average wood has about 50%. The balance is composed of lignin, polysaccharides other than cellulose and minor amounts of resins, proteins and mineral matter. In spite of its wide distribution in nature, cellulose for chemical purposes is derived commerically from only two sources, cotton linters and wood pulp. 

Since lignins are polymers of phenolics and are major plant constituents with resistance to microbial decomposition, they are the primary source of phenolic units for humic acid synthesis (178, 179). Once transformed, these humic acids become further resistant to microbial attack and can become bound to soils (180) form interactions with other high molecular weight phenolic compounds (ex. lignins, fulvic acids) and with clays (181) and influence the biodegradation of other organic substrates in soils (182, 183). 

Wood is a composite material that is made, up basically of a mixture of three main constituents, cellulose, hemicellulose, and lignin (see Textbox 54), all of them biopolymers synthesized by the plants, which differ from one another in composition and structure (see Textbox 58). The physical properties of any type of wood are determined by the nature of the tree in which the wood grows, as well as on the environmental conditions in which the tree grows. Some of the properties, such as the density of wood from different types of trees, are extremely variable, as can be appreciated from the values listed in Table 71. No distinctions as to the nature of a wood, whether it is a hardwood or a softwood, for example, can be drawn from the value of its specific gravity. 

The above outline of the evolution of the plant kingdom during coal-forming eras has been presented largely in the language of botanical anatomy. However, the alert chemist will note that the anatomical differences imply considerable quantitative and spatial differences in the distribution of the principal plant constituents [cellulose, lignin, cutin, suberin and other waxes, contents of protoplasmic cells, pigments, resins, sporopollenin. 

The method allowed the authors to characterise a pine pitch (viscous tar derived from the distillation of wood of pine trees). The main constituents detected by headspace SPME result from the pyrolysis of the lignin, guaiacol (11) and its p-w-alkyl derivatives [methyl... 

The two most important chemical constituents of wood are cellulose and lignin. Through the efforts of many investigators over the past... 

Nowadays there is scientific evidence that, besides plant polysaccharides and lignin, other indigestible compounds such as resistant starch, oligosaccharides, Maillard compounds, and phytochemicals—mainly polyphenols—can be considered DF constituents (Saura-Calixto and others 2000). Of these substances, resistant starch is a major constituent in cereals, whereas phytochemicals are the most important such substance in fruits and vegetables. Here, we address mainly polyphenols and carotenoids associated with DF in fruits and vegetables because of the important biological properties derived from them. 

Figure 1.15 gives an overview of the main constituents of non food biomass. There are three components Cellulose, hemicellulose and lignin. Cellulose and hemicellulose are built form sugar-type monomers, but their cost-effective isolation through enzymatic depolymerization remains a challenge. 

---