蚕丝脱胶废水的丝胶回收技术

Recovery technologies of sericin from silk degumming wastewater

丝胶位于蚕丝外层,是一种水溶性球状蛋白,具有丝胶Ⅰ、Ⅱ、Ⅲ、Ⅳ层状分布的特点;其二级构象以无规卷曲和β-折叠结构为主,几乎不含α-螺旋结构,其分子质量主要分布在10～100 kDa,且随脱胶方法的不同而异。丝胶具有胶体的性质,等电点为3.8～4.5,在一定湿热条件下会发生变性或变质。丝胶在化妆品、功能材料、食品添加剂等领域均具有良好应用前景,文中介绍了目前制丝废水中丝胶主要的化学和物理回收方法。化学法包括酸析法、有机溶剂法、化学混凝法、离子交换回收法;物理法包括离心法、冰冻法和超滤法,通过综合比较,提出一种新的丝胶回收方法。

Sericin is a globular protein wrapped in silk strands, and is water-soluble via a soap degumming process. Organic wastewater containing highly concentrated sericin is formed during this process. If the organic wastewater is discharged into rivers and other bodies of water, it poses serious threat in polluting the surrounding ecological system. However, sericin itself is a valuable natural resource with wide applications in the areas of cosmetics, clinical medicines, biomaterials and finishing process on health care textiles. Therefore, it is very critical to develop techniques to recover sericin contained in the wastewater of silk degumming. Sericin has natural laminar structures from sericin I to IV on the silk. The secondary structures of sericin consist of random coils and β sheet almost without the α-Helix structure. Its molecular weight widely ranges from about 10 to 100 kDa, depending on the degumming method. The sericin protein possesses characteristics of colloidal particles with isoelectric points of 3.8 -4.5, and may deteriorate or denature under the certain humid and high-temperature conditions. This review summarizes the main methods of sericin recovery from wastewater. The methods are based on chemical and physical principles and include acidic precipitation, organic solvent precipitation, chemical coagulation, ion exchange method, centrifugation, the freeze-method and the ultrafiltration method. A novel method based on current research is also proposed.