Hydrolysates enzymatic

The enzymatic hydrolysates of milk casein and soy protein sometimes have a strong bitter taste. The bitter taste is frequently developed by pepsin [9001 -75-6] chymotrypsin [9004-07-3] and some neutral proteases and accounted for by the existence of peptides that have a hydrophobic amino acid in the carboxyhc terminal (226). The relation between bitter taste and amino acid constitution has been discussed (227). 

These are major disadvantage of the esterase resolution process. Since die optimum pH of die enzymic reaction is generally on the alkaline side, die esters used as substrates are non-enzymatically hydrolysed and die optical purity of die L-amino adds obtained is generally low. Also the substrate has to be protected at the amino group in most cases in order to prevent formation of diketopiperasines. The esterase method is not attractive in practice and to the best of our knowledge is not used on an industrial scale. 

NSP content of soy bean meal and HWS was determined by the method of Englyst and Cummings [5]. The starch was enzymatically hydrolysed, the residue was dried and the sugar composition was determined. 

Table IV). Huff et al (11) extended these observations to include enzymatic hydrolysates of the native proteins and amino acid mixtures equivalent to soy or casein. In this experiment amino acid contents were identical among the diets fed as the three forms of each protein but the structure was different (Table V). 

Dietary treatment Intact casein Enzymatic hydrolysate Amino acid mixture... 

Arihara K, Nakashima Y, Mukai T, Ishikawa S, Itoh M. (2001) Peptide inhibitors for angiotensin I-converting enzyme from enzymatic hydrolysates of porcine skeletal muscle proteins. Meat Sci 57 319-324. 

Direct competition. The solid phase (a microtiter plate) is coated with an antibody specific for the antigen being assayed. The sample and enzyme-labelled antigen (antibiotic) are added. There is a competition for the antibody between the labelled and unlabelled antigen (antibiotic). Substrate is added and the color produced by the enzymatic hydrolyse is inversely proportioned to the concentration of antigen in the sample... 

For the analytical characterization of sulfated tyrosine peptides, spectroscopic methods as well as amino acid analysis and, more recently, mass spectrometry are employed. In Table 2 the spectroscopic data of tyrosine 0-sulfate are compared to those of the related sulfonic acid derivatives as possible byproducts in the chemical sulfation of the tyrosine or tyrosine peptides.[361 In the course of the synthesis of tyrosine 0-sulfate peptides and, particularly in the final deprotection step, desulfation may occur which limits the characterization of the final compounds in terms of quantitative identification of the tyrosine 0-sulfate. This is achieved by amino acid analyses of basic hydrolysates of the sulfated tyrosine peptides or preferably by analyses of the enzymatic hydrolysates with aminopeptidase M or leucine-aminopeptidase. 

Setlow et al.83 have studied the photolysis of poly dl poly dC (polydeoxyinosinic acid polydeoxycytidylic acid, see Glossary) and poly dA dT. The photochemical changes were estimated by following absorbance changes, by chromatographic separation of acid hydrolysates, and by chromatographic separation of products from enzymatic hydrolysates. 

Flavorzyme is a commercially available proteolytic enzyme preparation by Novo Nordisk Bioindustrials. It can be used to obtain a meat-like process flavouring from defatted soybean meal. With the help of aroma extract dilution analysis, Wu and Cadwallader [61] showed in their study of 2002 the presence of key aroma compounds of roasty, meat-like aroma in the enzymatically hydrolysed and heated hydrolysed protein, e.g. maltol, furaneol, methanethiol and furanthiol derivatives. 

FIGURE 4.1 Schematic diagram of the three-step recycling membrane reactor for production and separation of enzymatic hydrolysates. PI, pressure indicator FI, flow indicator pHIC, pH indicator controller FSEH, first hydrolysates SSEH, second hydrolysates TSEH, third hydrolysate. 

FIGURE 4.5 p-Secretase-inhibitory activity of various enzymatic hydrolysates from marine zooplankton, rotifer (Byun et ai, 2009a). 

Huang, R., Li, N., Zeng, Q., Deng, Q., and Chen, B. (2011). Extraction and separation of angiotensin-converting enzyme inhibitor from enzymatic hydrolysate of oyster. Adv. Mat. Res. 236, 2610-2614. 

Liu, Z., Zeng, M., Dong, S., Xu, J., Song, H., and Zhao, Y. (2007). Effect of an antifungal peptide from oyster enzymatic hydrolysates for control of gray mold (Botrytis cinerea) on harvested strawberries. Postharvest Biol. Technol. 46, 95-98. 

Hernandez-Ledesma, B., D avalos, A., Bartolom e, B., and Amigo, L. (2005). Preparation of antioxidant enzymatic hydrolysates from a-lactalbumin and p-lactoglobulin. Identification of active peptides by HPLC-MSMS. ]. Agric. Food Chem. 53,588-593. 

Jun, S. Y., Park, P. J., Jung, W. K., and Kim, S. K. (2004). Purification and characterization of an antioxidative peptide from enzymatic hydrolysates of yellowfin sole (Limanda aspera) frame protein. Eur. Food Res. Technol. 219, 20-26. 

Hsu, . C., Li-Chan, E. C. Y., and Jao, C. L. (2011). Antiproliferative activity of peptides prepared from enzymatic hydrolysates of tuna dark muscle on human breast cancer cell line MCF-7. Food Chem. 126, 617-622. 

Ohba, R., Deguchi, T., Kishikawa, M., Arsyad, F., Morimura, S., and Kida, K. (2003). Physiological functions of enzymatic hydrolysates of collagen or keratin contained in livestock and fish waste. Food Sci. Technol. Res. 9, 91-93. 

Human serum sample (0.5 ml), diluted with 2.5 ml of 0.1 N NaOH is incubated at 65°C for 15 min. The free, and glycine- and taurine-conjugated fractions are isolated by means of solid-phase extraction, using BE C18 and BE SAX cartridges in succession [23]. The taurine fraction is enzymatically hydrolysed according to a previously described method [24]. The final residue is treated with 1 ml volume of 0.01% (w/v) KOH methanolic solution (methanokwater 1 9, v/v) at 40°C by ultrasonication for 3 min. Then, 0.2 ml of the obtained suspension is derivatised as described below. BA content is determined in each sample by comparison with an appropriate standard solution. 

The chromatogram of free BA standard mixture is reported in Fig. 5.4.7. The Br-AMN degradation products are eluted at lower retention times than derivatised BA, close to the solvent front, so they do not impair BA separation. Free BA fraction also encloses taurine conjugates, previously enzymatically hydrolysed. The separation of glycine conjugated BA is illustrated in Fig. 5.4.8. In both chromatograms, the peaks of BA naphthacyl esters are fully resolved and separated from the reagent peaks. 

Bioactive peptides Enzymatic hydrolysate Milk, casein... 

Stereoselective enzymatic hydrolyses of esters represent a further type of biotransformation that has been used for the synthesis of optically active organosilicon compounds. The first example of this particular type of bioconversion is illustrated in Scheme 15. Starting from the racemic (l-acetoxyethyl)silane rac-11, the optically active (l-hydroxyethyl)silane (5)-41 was obtained by a kinetic racemate resolution using porcine liver esterase (PLE E.C. 3.1.1.1) as the biocatalyst7. The silane (5)-41 (isolated with an enantiomeric purity of 60% ee bioconversion not optimized) is the antipode of compound (R)-41 which was obtained by an enantioselective microbial reduction of the acetylsilane 40 (see Scheme 8). 

Scheme 15)62. After terminating the reaction at a conversion of 38% (relative to total amount of substrate rac-78), the product (S)-43 was separated from the nonreacted substrate by column chromatography on silica gel and isolated on a preparative scale in 71% yield (relative to total amount of converted rac-78) with an enantiomeric purity of 95% ee. Recrystallization led to an improvement of the enantiomeric purity by up to >98% ee. The biotransformation product (S)-43 is the antipode of compound (/ )-43 which was obtained by enantioselective microbial reduction of the acylsilane 42 (see Scheme 8)53. The nonreacted substrate (/ )-78 was isolated in 81% yield (relative to total amount of nonconverted rac-78) with an enantiomeric purity of 57% ee. For further enantioselective enzymatic hydrolyses of racemic organosilicon esters, with the carbon atom as the center of chirality, see References 63 and 64. 

Ethanol Production in Immobilized-Cell Bioreactors from Mixed Sugar Syrups and Enzymatic Hydrolysates of Steam-Exploded Biomass... 

Enzymatic hydrolysates of various proteins have a bitter taste, which may be one of the main drawbacks to their use in food. Arai el al. [90] showed that the bitterness of peptides from soybean protein hydrolysates was reduced by treatment of Aspergillus acid carboxypeptidase from A. saitoi. Significant amounts of free leucine and phenylalanine were liberated by Aspergillus carboxypeptidase from the tetracosapeptide of the peptic hydrolysate of soybean as a compound having a bitter taste. Furthermore, the bitter peptide fractions obtained from peptic hydrolysates of casein, fish protein, and soybean protein were treated with wheat carboxypeptidase W [91], The bitterness of the peptides lessened with an increase in free amino acids. Carboxypeptidase W can eliminate bitter tastes in enzymatic proteins and is commercially available for food processing. 

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