Category Archives: Biomass Recalcitrance

Chemistry of cell wall proteins

Proteins are ubiquitous components of plant cell walls where they may account for as much as 10% of the dry weight of the wall. The wall proteins include enzymes, wall loos­ening proteins (expansins) (71), and signaling molecules (AGPs) (70) but the structural proteins are quantitatively the most important. These include the glycine-rich proteins (GRP) (72, 73), the hydroxyproline-rich glycoproteins (HRGP, […]

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GDP-$-L-fucose (GDP-Fuc)

Plant cell wall polysaccharides contain L-fucose (6-deoxy-L-Gal) derived from the sugar — donor, GDP-Fuc. GDP-Fuc synthesis occurs in two enzymatic steps (similar to the synthesis of UDP-Rha from UDP-Glc). These enzymes have been characterized and the corresponding functional genes have been identified in humans, plants, and bacteria. First, GDP-Man 4,6-dehydratase (GMD), converts GDP-Man to a GDP-4keto-6-deoxyMan intermediate. The latter is […]

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Lignin isolation procedures

In spite of their intractable nature, lignins can be fully removed, but only under quite drastic chemical conditions using either strong acid [e. g., sulphite pulping processes (147-150)] or alkaline [e. g., kraft (8)] conditions at elevated temperatures and pressures. They can also be partially removed using milder procedures, such as by extensive ball milling for 4-5 days followed by […]

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Plant cell wall breakdown by eukaryotic microorganisms

12.3.1 Rumen fungi Rumen anaerobic fungi, which are related to chytrids (66), have been shown to produce highly active cellulase systems (67) and have been the source of recombinant enzymes with high specific activities that have attracted interest for a variety of biotechnological applications [e. g. (68, 69)]. As in cellulolytic bacteria, individual enzyme structures show multidomain organization (70). Furthermore, […]

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Biochemical approaches to define biomass degrading communities

Extracellular enzymes catalyze the initial rate-limiting step of decomposition and are the primary means by which microbes degrade complex biomass into smaller molecules that can be assimilated. Therefore, it is reasonable to assume that determining the amount and type of hydrolytic activities associated with biomass can be an indicator of the hydrolytic po­tential of a given microbial community. Defining biomass […]

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Degradabilities of the walls of different cell types by enzymes

The degree of recalcitrance of cell wall polysaccharides to depolymerization by enzymes, or other hydrolytic reagents, depends on the ability of the enzymes to access their substrates in the walls. This is manifest at two levels. The first relates to the surface area ofthe wall exposed to the hydrolytic agent: the greater the extent of comminution of the feedstock, the […]

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Fermentation and nucleotide-sugars: a long history

It was exactly 101 years ago, while working on fermentation of sugars by yeast, that Harden and Young (408) first reported the chemistry and metabolic roles of sugar-phosphates. Later, different types of sugar kinases from yeast, muscle, and plant sources were identified that were able to convert sugar (monosaccharide) and ATP to the phosphorylated-sugar esters. The seminal work by Cori […]

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