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ABSTRACT
Chitosan was prepared from ß-chitin, which was isolated from squid pens (Loligo chenisis). The effects of the NaOH concentration, reaction temperature and the time of the deacetylation and degradation processes were investigated.The degree of deacetylation was over 90%, established using a two-time deacetylation method. ß-chitin was firstly treated in a 4% NaOH solution at 80°C for 8h and then washed with water until it became neutral, before treating it in the same solution at 90°C for another 4 h. The chitosan had a degree of deacetylation of 91% and a molecular weight of 1740 kDa and PDI of 1.6.
Keywords: Deacetylation, ß-chitin, Chitosan, Squid pens, Loligo chenisis.
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1. INTRODUCTION
Chitosan is a product of a thermochemical alkaline deacetylation of chitin, where the acetyl (-COCH3) groups in N-acetyl-D-glucosamine (NADG) units were removed (Fig. 1). Chitosan was reported to have much a higher activity than that of chitin due to its amine groups. Moreover, chitosan can be dissolved in low acidic concentrations, which improved the processing of chitosan in its applications. In fact, chitosan was produced commercially from shrimp and crab shells with different degree of deacetylations (DD) and molecular weights (Mw),[1-4] which were the important parameters for applying the chitosan in special cases. It reported that the antibacterial and antifungal activities of chitosan were much depended on its DD and Mw.[5'2'6'7] Therefore, it is necessary to choose the proper source and the deacetylation conditions to prepare the high quantity chitosan for any applications.
The deacetylation of chitin has been studied in many published works.[8-16]The aim of deacetylation is remove completely the acetyl groups in chitin chains but the Mw of chitosan was reduced slightly. Lamarque and Domard[11,10] investigated the deacetylation of chitin by a multiple-step method in 50%(w/v) NaOH solution at 80-110°C for both a- and ßchitin. By using this method, the structure of chitin was swollen, which improved the deacetylation of chitin. The obtained chitosan had a DD of 90,3% and Mw of 1340 kDa (for ßchitosan) and Mw of 820 kDa(for a-chitosan), which was much higher than that of chitosan using one-step method (Mw of ca. 160 kDa. Youn et al.[17] conducted the deacetylation of chitin from squid pens in 45wt.% NaOH solution at 121 °C and...