长牡蛎贝壳不同部位的几丁质提取及鉴定

Extraction and identification of chitin from different parts of the shell in Crassostrea gigas

几丁质是贝壳有机框架的重要组成成分,在贝类生物矿化中发挥着重要作用,然而贝壳不同部位的几丁质含量与类型是否存在差异,目前还未有报道。本研究通过脱钙、脱蛋白、漂白的方法分别从长牡蛎贝壳的壳膜、贝壳表面的角质鳞片、贝壳内侧的棱柱层与片层结构中提取到粉末状固体,并通过傅里叶红外光谱(Fourier Transform Infrared Spectroscopy,FTIR)对提取产物进行鉴定,发现这3个部位的提取产物均具有几丁质的特征吸收峰。通过对比3个部位提取产物的吸收峰,发现壳膜和角质鳞片中提取到的几丁质产物FTIR结构较为相似,其结构特征更接近于β-几丁质;而在富含钙质的棱柱层及片层结构中,几丁质提取产物在1620~1660 cm^(-1)波数处有两个特征吸收峰,其结构更接近于α-几丁质。在长牡蛎壳膜、角质鳞片及贝壳内侧的几丁质提取物的含量分别为:(15.14±1.13)%、(4.52±0.85)%、(0.27±0.12)%。3个部位中,壳膜主要由几丁质和基质蛋白构成,角质鳞片则积累了更多钙质,而贝壳内侧的棱柱层与片层结构中含有大量的碳酸钙,这导致壳膜中提取产物得率最高,而在贝壳内侧提取产物得率显著下降。

Chitin is a vital component of the shell organic framework and plays an important role in molluscan shell biomineralization.However,the content and type of chitin in different parts of the shell has not been reported.In this study,by decalcification,deproteinization and decolorization,chitin powder was extracted from the shell periostracum,the cuticle scales on the shell surface,and the prismatic layer and lamellar structure inside the shell from the Pacific oyster Crassostrea gigas.The extracted products were identified by Fourier Transform Infrared Spectroscopy(FTIR),and it was found that all three different parts had characteristic absorption peaks of chitin.The results showed that the structures of the products obtained from the shell periostracum and the cuticle scales were similar,and the spectra of the products were closer to theβ-chitin,while the products obtained from the prismatic layer and lamellar structure were more similar to theα-chitin structure with two characteristic absorption peaks at 1620~1660 cm^(-1).The yield of products from these three different parts of the oyster shell was(15.14±1.13)%,(4.52±0.85)%and(0.27±0.12)%respectively.The shell periostracum is mainly composed of chitin and structural proteins.The cuticle scales accumulate more calcium and the prismatic layer and lamellar structure inside the shell contain a large amount of calcium carbonate.The yield of the three products decreased significantly,probably due to the large amount of carbonate in the calcareous the prismatic layer and lamellar structure.