Enzymatic hydrolysates molecular weights

The preferred route for reducing the molecular weight of PVA involves chain scission at the 1,3-diketone site (see Fig. 6). As the diketone element is chemically not very stable, a spontaneous degradation of oxidised PVA was also discussed [80]. Nevertheless, the preferred degradation pathway is most likely the biochemical process because enzymes were identified that showed high activity with diketone substrates [81], especially with oxidised PVA. The p-diketone hydrolase (BDH EC 3.7.1.7) hydrolyses aliphatic p-diketones to form methyl ketones and carboxylic acids in equimolar amounts [82]. The enzymatic cleavage of C-C bonds in p-diketones is not well studied [83]. BDH enzymes could be isolated from different PVA-degrading strains, purified, characterised and cloned [84]. 

Many workers have studied the influence of enzymatic hydrolysis on the functional properties of various food proteins, and much of this work has recently been reviewed by Richardson (2). However, there seem to be very few reports which quantitatively relate functionality to parameters which characterize the protein hydrolysates per se (e.g. molecular weight). Ricks et al. (3 ) examined the solubility and taste of a number of pure proteins (denatured pepsin, lactoblobulin, a-Sj -, K-, and 8-casein) hydrolysed with... 

The precursor of pepsin is pepsinogen (MW 40,000) and is converted into active pepsin in the gastric juice by the enzymatic action of pepsin itself. In this conversion, 42 amino acid residues are removed from the amino-terminal end of the polypeptide chain. The portion of the molecule that remains intact is enzymatically active pepsin of molecular weight 33,000 Dalton. Pepsin hydrolyses proteins at peptide bonds on the amino terminal side of tyrosine, phenylalanine and tryptophan and converts it into a mixture of smaller peptides. 

Enzymatic hydrolysis of polysaccharides (cellulose, starch) or oligosaccharides (maltose, saccharose, lactose) for the synthesis of food products is another class of processes MBR have been applied to. Paolucci-Jeanjean et al [4.56] have recently reported, for example, the production of low molecular weight hydrolysates from the reaction of cassava starch over a-amylase. In this case the UF membrane separates the enzyme and substrate from the reaction products for recycle. Good productivity without noticeable enzyme losses was obtained. Houng et al [4.57] had similar good success with maltose hydrolysis using the same type of MBR,... 

First the substrate must be an enzymatic protein hydrolysate (consisting of a mixture of low-molecular-weight peptides) with an average molecular weight less than 1000 [50] between 450-1450 [51], with soy proteins 1043 and 635 [52]. 

Proteolysis has been widely used to improve the surface properties of proteins [3,4]. Partial proteolysis may facilitate the unfolding of polypeptides and increase the heterogeneity of the protein, that is, the peptide molecular weight distribution, resulting in improved surface properties. The factors affecting enzymatic hydrolysis as well as the production of protein hydrolysates are described in detail in Chapter 2 of this book. In this section, therefore, we show only examples of the systematic approach on a structural factor relating to amphiphilic or amphoteric properties of peptides produced by proteolysis. 

Description. These surfactants are formed from hydrolyzed proteins (e.g., animal coUagen). Depending on the protein hydrolysis process (chemical or enzymatic), the average polypeptide molecular weight can vary from about 350 to 2000 and some free amino acids may be present in the hydrolysate. 

---