Preparation of Low Molecular Weight Chitosan by Complex Enzymes Hydrolysis

Abstract

Through the determination of viscosity average molecular weight, enzyme activity, hydrolysis ratio and reducing sugar concentration, the optimal technological conditions of complex enzymes composed of commercial α-amylase, cellulase and pectinase were investigated. Results indicated that complex enzymes could result in low molecular weight chitosan ranged from 1000 to 4000 after enzymatic degradation for 2 h under the condition of zymolyte ratio 1:5(m/m), pH 5.3 and temperature 56℃, and the structure of those products failed to vary obviously by FTIR analysis.Keywords: Chitosan, Low molecular weight chitosan, Complex enzymes, Preparation Chitosan (chitosan, CTS) is a kind of natural polysaccharide bioactive substances containing nitrogen, tends to be the sixth largest life elements excluding the body necessities viz. sugar, protein, fat, fiber and minerals, and exerts an extensive and intensive application in food, cosmetic and pharmaceutical areas (Zhu, 2006, PP. 41-45; Jiang, 2006, PP. 99-102). Due to its large molecular weight and the structure containing abundant hydrogen bonds, chitosan is only soluble in dilute acid, insoluble in water, and tough to be assimilated by human bodies, which hinders its application dramatically. If chitosan was degraded into LMWC (low molecular weight chitosan) with the molecular weigh less than 10000, its water solubility increased greatly, conducive to human intestinal digestion and absorption, and possessed the functions such as promoting to produce splenic antibody, and lowering cholesterol, blood pressure, blood sugar and blood lipid level in serum and liver (Wei, 2003, PP. 614-617; Kim, 2005, PP. 357-368).Recently, studies on the preparation of water soluble LMWC have attracted many researchers' attention all over the world (Huang, 2002, PP. 381-385). Degradation methods initiated by scholars mainly included chemical, physical and enzymatic degradation. Among them, enzymatic degradation has been recognized as one of the most promising approaches to prepare LMWC, because its reaction condition was moderate without byproducts and the degradation process was easy to monitor. However, the specific enzyme for chitosan was expensive, and its application in industry was limited. The applications of single non-specific enzyme in hydrolyzing chitosan such as α-amylase (Yu, 2008, PP. 464-466; Zhang, 2003, PP. 44-48), pectinase (Ipsita, 2003, PP. 582-588; Cabrera, 2005, PP. 165-172), cellulose (Lin, 2009, PP. 47-53; Xia, 2008, PP. 6751-6762; Han, 2007, PP. 98-101;Xie, 2009, PP. 1895-1899, protease (Li, 2005, PP. 441-448) and so on have been documented, but those enzymes showed limited effects on degradation, even if enhancing their amount. Consequently, we investigated effects of complex enzymes containing cellulase, pectinase and α-amylase on chitosan degradation.

Structural Characterization of Oligochitosan Elicitor from Fusarium sambucinum and Its Elicitation of Defensive Responses in Zanthoxylum bungeanum

“…The carbohydrate content of chitosan and each oligochitosan fraction was measured spectrophotometerically by the 3,5-dinitrosalicylic acid (DNS) method [77]. The DNS reagent contained a 1:1:1:1 volumetric mixture of 3,5-dinitrosalicylic acid (1%), Rochelle salt (40%), phenol (0.2%), and potassium bisulfate (0.5%), all dissolved in sodium hydroxide (1.5%).…”

Antibacterial Activity and Physical Properties of Edible Chitosan Films Exposed to Low-pressure Plasma

“…Enzymatic hydrolysis leads to chitosan degradation and results in lower molecular weight. Xie (2011) observed that complex enzymes composed of commercial cellulose, pectinase and α-amylase degrade the large molecular chain of chitosan, and as a consequence, molecular weight lowered from 1,000,000 to 100,000. According to Tatro et al (2003), lower thermal stability is caused by decreasing of molecular weight.…”

Enzymatic Depolimerization of Chitosan for the Preparation of Functional Membranes

“…Greater intensity is observed in the spectral signals of the QsD because the functional groups vibrate with greater freedom of movement because the steric hindrance of the polymer chain decreases. e increase in the intensity of the signal at 3379 cm −1 is due to a greater number of OH groups, while the intensity of the signal at 3260 cm −1 is associated with the greater number of NAcGlc units due to the increase of the AD [27]. e conservation of the signals of absorption of the glycoside bond and the pyranosic ring con rms that the mechanism of action of the enzyme complex is selective at the site of the β (1-4) glycoside bond.…”

“…® . At concentrations higher than 1 mg•mL −1 of the enzyme system, degradation is maximal, and up to a limit value of 2.75 × 10 −3 mg•mL −1 , the synergistic e ect of the enzyme system can be considered constant [27]; after this value, the concentration of reducing sugars is constant (Figure 3). A substrate concentration of 1 : 10 was maintained.…”