Hydrolysis of biopolymers

There is currently little understanding of the influence of interfacial composition and (nano)structure on the kinetics of enzymatic hydrolysis of biopolymers and lipids. However, a few preliminary studies are beginning to emerge (McClements et al., 2008 Dickinson, 2008). Thus, for example, Jourdain et al. (2009) have shown recently that, in a mixed5 sodium caseinate + dextran sulfate system, the measured interfacial viscosity increased from qs = 220 mN s m 1 without enzyme to qs = 950 mN s m 1 with trypsin present. At the same time, the interfacial elasticity was initially slightly reduced from (7S = 1.6 mN m 1 to (h = 0.7 mN m, although it later returned to close to its original value. Conversely, in the... 

These two processes may be coupled because hydrolysis of biopolymers may contribute to the production of various free monomers such as DFAA and monosaccharides. Polymers and other macromolecules must be hydrolyzed first to LMW compounds (approximately 500 Da) before transport by... 

Yeast autolysis could be defined as the hydrolysis of biopolymers under the action of hydrolytic enzymes which releases cytoplasmic (peptides, amino acids, fatty acids and nucleotides) and cell wall (glucans, mannoproteins) compounds into the wine (Alexandre et al. 2006).Usually, autolysis takes place at the end... 

TEOS is of considerable current use on an industrial scale owing to some advantages over sodium metasilicate. Limitations on the sol-gel processing with TEOS arise in the entrapment of biopolymers in silica. They are caused primarily by the alcohol that is separated in the course of precursor hydrolysis Equation (7). Most... 

Optically active 3-hydroxybutanoic acid and its methyl ester were first prepared by McKenzie, Magnus-Levy, and Emil Fischer.3 The biopolymer PHB and mixed polymers containing (R)-3-hydroxybutanoate and (R)-3-hydroxypentanoate were also discovered long ago,4 5 and are now produced on an industrial scale. .7 As described here, depolymerization by transesterification [H+ or Ti(OR)4 catalysis], or by hydrolysis, produces8-9 the corresponding monomeric (R)-esters and (R)-acids 1. The 3-hydroxybutanoic acid can also be prepared by hydrolysis of the ester.2-10... 

The aliphatic components of SOM, derived from various sources, tend to persist in soil (Almendros et al. 1998 Lichtfouse et al. 1998a Lichtfouse et al. 1998b Mosle et al. 1999 Poirier et al. 2000). The principal source of aliphatic materials in soil is plant cuticular materials, especially cutin, an insoluble polyester of cross-linked hydroxy-fatty acids and hydroxy epoxy-fatty acids (Kolattukudy 2001). Some plant cuticles also contain an acid and base hydrolysis-resistant biopolymer, comprised of aliphatic chains attached to aromatic cores known as cutan (Tegelaar et al. 1989 McKinney et al. 1996 Chefetz 2003 Sachleben et al. 2004). 

Enzymatic Hydrolysis in the Presence of Biopolymer Adsorbed Layers... 

Lignin is a high-energy content biopolymer rich in phenolic components. It provides structural integrity to plants. The combination of hemicellulose and lignin provide a protective sheath around the cellulose and this sheath must be modified or removed before efficient hydrolysis of cellulose can occur. 

The typical biopolymers used for the preparation of micro- and nanogels are polysaccharides (Scheme 11) cellulose (CL), chitosan (CS), hyaluronan (HA), heparin, pullulan (PuL), dextran, and gelatin - a proteinaceous polyamolytic gel obtained by partial hydrolysis of collagen. Gelatine microgels are addressed by Landfester and Musyanovych in another chapter of this issue [5] and will thus not be discussed further here. 

For instance, denaturation and partial hydrolysis of proteins oppositely influence their incompatibility with other biopolymers (Tolstoguzov 1991). Most biopolymers are polyelectrolytes. Factors such as pH and salt concentration affect their interactions with one another, with the solvent and their compatibility. For instance, when the pH is shifted to their isoelectric point (lEP), the thermodynamic incompatibility of proteins is usually enhanced by self-association of the protein molecules. Generally, protein-neutral polysaccharide mixtures separate into two phases when the salt concentration exceeds 0.15 M. 

In addition to the application of ABRE in wood chemistry, it has been widely applied to other biomass conversion fields, particularly enzyme catalysed hydrolysis reactions such as the conversion of biopolymers (including cellulose and starch) to monosaccharides and oligosaccharides. In this area, PEG ABS systems offer a benign non-denaturing environment in contrast to organic solvent reaction media. 

Table 3.7 Comparison of stabilities of biopolymers towards hydrolysis in the absence of enzymes (after Wolfenden et al. 1998 Thompson et al. 1995). Protein values are based on glycine-glycine units see Box 5.4 for explanation of half-life...

Cutin and suberin are lipid biopolymers of variable composition which are part of the protective outer coatings of all higher plants. Chemically, cutin and suberin are closely related polyesters composed of long-chain fatty and hydroxy fatty acid monomers. Both types of biopolymers represent labile, easily metabolizable terrigenous organic matter because they are sensitive to hydrolysis. After sedimentation, they have only a moderate preservation potential. 

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