Chitosan hydrolysis process

A possibility of using the viscosimetiy and sedimentation and diffusion methods in studying the process of enzyme chitosan hydrolysis is discussed in the chapter. It is shown that a change in the intrinsic viscosity of chitosan may be determined by both the hydrolysis process in the glycoside bonds and transformation of the supramolecule stmcture of the polymer. Thus, for setting the hydrolysis process it is necessary to use an absolute method for molecular weight determination. 

However, few researches have been reported on the mechanism of these non-specific enzymatic processes, and even then controversial views exist. On the one hand, Kittur et al.[33] first reported that a multiple functional pectinase isoform from Aspergillus niger co i A be responsible for chitosan degradation by pectinases,but on the other hand, some authors have purified hetero chitosanases or/and chitinases from several commercial proteases,which were charged with their chitosanolytic activity [51-53].Whereas,no reports have been focused on non-specific hydrolysis of cellulases and lipases before, although their utility were popular in chitosan hydrolysis[5,8,9,10,28-31,43] and several bifunctional cellulase-chitosanases have been reported to be secreted from bacteria [58,79,87]. 

Monoglyceride (MG) is one of the most important emulsifiers in food and pharmaceutical industries [280], MG is industrially produced by trans-esterification of fats and oils at high temperature with alkaline catalyst. The synthesis of MG by hydrolysis or glycerolysis of triglyceride (TG) with immobilized lipase attracted attention recently, because it has mild reaction conditions and avoids formation of side products. Silica and celite are often used as immobilization carriers [281], But the immobilized lipase particles are difficult to reuse due to adsorption of glycerol on this carriers [282], PVA/chitosan composite membrane reactor can be used for enzymatic processing of fats and oils. The immobilized activity of lipase was 2.64 IU/cm2 with a recovery of 24%. The membrane reactor was used in a two-phase system reaction to synthesize monoglyceride (MG) by hydrolysis of palm oil, which was reused for at least nine batches with yield of 32-50%. 

Acid hydrolysis of chitosan followed by the HPLC detection of the amount of acetic acid liberated is able to give acetyl content of chitin/chitosan. Due to the high sensitivity, availability, easiness of method and effectiveness in detection of functional groups IR spectroscopy can give usefid information about the acetyl content of chitin/chitosan as well as possible cross-contaminations. The results of Differential Thennogravimetric Analysis (DTA) show increased thermostability compared to GlcNAc. Discussed biopolymer shows its main thermal process from 275 to 280 °C respectively. 

Several procedures for the preparation of chitin and chitosan from different shellfish wastes have been developed over the years, some of which form the basis of the chemical processes used for the industrial production of chitin and derivatives (Femandez-Kim 2004). A representation of current industrial chitin processes are sununarized in Figure 2.3. Industrial techniques for chitin and chitosan extraction from different shell waste streams normally rely on harsh chemical processes due to covalent associations with other shell constituents. These methods generate large quantities of hazardous chemical wastes and partial DA of chitin and hydrolysis of the polymer may occur, leading to inconsistent physiological properties in the end products (Andrade et al. 2003, Kim and Mendis 2006). 

IR and NMR spectroscopy are relatively easy-to-apply for a qnaUtative and comparative evaln-ation of the chemical structure and the DA determination. These techniques are nondestructive methods and do not need initial treatment such as hydrolysis, pyrolysis, and derivatization. This chapter describes the structural characterization of chitin and chitosan (as oligomers and polymers) by IR, near-IR, and various types of NMR spectroscopy techniques. This study provides information on (1) composition, sequence, and type of residues and (2) any structural changes occurring in the molecules as a result of different processes (degradation, deacetylation, and acetylation). The influences of acids, alkali, moisture, and impurities on the NMR and IR spectra of the original molecules will be also discussed. 

Sikorski, P., Sprbotten, A., Horn, S.J., Eijsink, V.G., and Varum, K.M. 2006. Serratia marcescens chitinases with tunnel-shaped snbstrate-binding grooves show endo activity and different degrees of processivity during enzymatic hydrolysis of chitosan. Biochemistry 45 9566-9574. 

Kou, C. H., Chen, C. C., and Chang, B. H. 2004. Process characteristics of hydrolysis of chitosan in acontinues membrane reactor system. Journal of Food Science 69 332-337. 

Indeed, the use of biological treatment instead of chemical treatment for the isolation of chitin from crustacean shells as well as for production of chitosan will substantially reduce environmental pollution. The use of chitin deacetylase for the preparation of chitosan polymers and oligomers offers the possibility to develop an enzymatic process that could potentially overcome most of the drawbacks discussed earlier [59]. As shown in Fig. 4, chitin deacetylase (CDA EC 3.5.1.41) catalyzes the hydrolysis of A-acetamido bonds in chitin to produce chitosan. The presence of this enzyme has been reported in several fungi and insect species [60-68]. 

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