Extraction of highly purified chitosan from shrimp shells with high de-acetylation degree

chitin and chitosan, as the most abundant amino-polysaccharide in nature, have characteristics such as biocompatibility, low toxicity, and biodegradability. These unique specifications have resulted in chitin and chitosan attracting a lot of attention because of the high potential for producing valuable products. Chitosan has many uses in the agricultural industry and wood preservation, such as pesticides and insecticides, as well as in biomedical applications, including the use in the pharmaceutical industry as a drug release, and can also be used as drug carriers. The purpose of this article is to extract highly purified chitosan with high de-acetylation degree from shrimp shells.

In this study, the extraction and characterization of chitosan from the shrimp shell (Litopenaeus vannamei) was investigated. For this purpose, chitosan was extracted by chemical method including mineralization (with 4% HCl concentration), protein degradation (with 4% NaOH concentration), and deacetylation (with 60% NaOH concentration). Also, nano-chitosan was prepared by ionic gelation method. A series of parameters were studied, which included the degree of deacetylation, molecular weight, pH and solubility. Also, FTIR spectroscopy, FESEM scanning electron microscopy, Zeta potential, X-ray diffraction spectroscopy (EDX) and X-ray diffraction (XRD) were used.

The results of FTIR test on chitin and chitosan extracted from shrimp shell showed that the removal of protein and mineral materials was appropriate with the use of hydrochloric acid, sodium hydroxide. The high degree of deacetylation of chitosan in this study (87%) had a significant effect on the proper solubility and low viscosity of chitosan. The solubility of chitosan in acetic acid was 86%. The molecular weight of the chitosan extracted was 110 kDa. With this molecular weight, chitosan can be used well in the pharmaceutical industry. According to chitosan XRD patterns in previous studies, the peaks obtained in XRD patterns in this study confirmed the semi-crystalline structure of chitosan. Due to the change in the level of chitosan seen in FESEM images, it can be due to the purification of chitosan. The FESEM test confirms nano-chitosan with diameter range of 100 to 150 nm.

From the results of this study, it can be concluded that using the chitosan extraction method in this research, highly purified chitosan with high de-acetylation degree can be obtained. With increasing degree of deacetylation, the solubility of chitosan has increased, and this degree of deacetylation has had a significant effect on improving molecular weight (Low molecular weight). As a result of the study of the role of solubility of chitosan in the vicinity of acetic acid, it becomes obvious that the solubility of the chitosan and the size of the nano-chitosan particles depend on the solution pH. The produced chitosan can be used in wide variety of application mainly in pharmaceutical industry.