The low solubility in common solvent and high viscosity resulting from its high molecular weight (MW) with fiber-like structure prevents a more widespread use of chitosan. This paper presents a performance comparison of nonspecific, commercially available enzymes, α- and β-amylases, for the hydrolysis of chitosan to lower its MW. The results showed that both enzymes demonstrate the ability to be used as catalysts in chitosan hydrolysis with β-amylase having better performance than α-amylase. The chitosan hydrolysis was influenced by not only the enzyme and the chitosan characteristics but also the hydrolysis condition. The optimum pH solution was 4 for α-amylase and 5 for β-amylase. The hydrolysis temperature was found to be optimal at 90 and 50°C for α- and β-amylases, respectively. 1. Introduction Chitosan is a natural polysaccharide composed of β-(1-4) linked 2-amino-2-deoxy-D-glucopyranose and 2-acetamido-2-deoxy-D-glucopyranose, which is nontoxic, biodegradable, and biocompatible. Chitosan is commercially produced by deacetylation of chitin, which can be extracted from the exoskeleton of crustaceans (such as shrimp, lobster, crabs, and fish) and cell walls of fungi [1, 2]. Chitosan has been considered as a functional biopolymer, which is widely used in various industrial applications such as food and nutrition, medical and pharmaceutical, and cosmetic industries as well as environmental and agricultural industries [1–5]. Nevertheless, its low solubility in common solvent and high viscosity caused by its high molecular weight with fiber-like structure prevents a more widespread use of chitosan especially in food and medical applications. It was reported that low molecular weight chitosan (LMWC) that has an average molecular weight within the range 5000–10000？Da exhibits better biological activities than high molecular weight chitosan (HMWC) [4, 6]. Further, this LMWC had potential as a DNA delivery system [7]. Kondo et al. reported that LMWC with 20？kDa restricts progression of diabetes mellitus and displays higher affinity for lipopolysaccharides than 140？kDa chitosan [8]. Other studies showed that LMWC exhibits special biological and chemical activities such as antimicrobial activity [3, 9, 10], antifungal [11, 12], and antitumor activity [13, 14]. Therefore, lowering chitosan molecular weight to produce more water soluble chitosan (chitosan oligosaccharides) is gaining increased importance for broadening chitosan applications especially in food and biomedical industries. Several methods have been proposed to lower chitosan molecular weight. In
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