title: Structural diversity requires individual optimization of ethanol concentration in polysaccharide precipitation.
abstract: Ethanol precipitation is one of the most widely used methods for preparing natural polysaccharides, in which ethanol concentration significantly affects the precipitate yield, however, is usually set at 70-80%. Whether the standardization of ethanol concentration is appropriate has not been investigated. In the present study, the precipitation yields produced in varied ethanol concentrations (10-90%) were qualitatively and quantitatively evaluated by HPGPC (high-performance gel-permeation chromatography), using two series of standard glucans, namely dextrans and pullulans, as reference samples, and then eight natural samples. The results indicated that the response of a polysaccharide's chemical structure, with diversity in structural features and molecular sizes, to ethanol concentration is the decisive factor in precipitation of these glucans. Polysaccharides with different structural features, even though they have similar molecular weights, exhibit significantly different precipitation behaviors. For a specific glucan, the lower its molecular size, the higher the ethanol concentration needed for complete precipitation. The precipitate yield varied from 10% to 100% in 80% ethanol as the molecular size increased from 1kDa to 270kDa. This paper aims to draw scientists' attention to the fact that, in extracting natural polysaccharides by ethanol precipitation, the ethanol concentration must be individually optimized for each type of material.
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, 7 Baptist University Road, Kowloon Tong, Hong Kong.
authors.forename: Jun
authors.initials: J
authors.lastname: Xu
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, 7 Baptist University Road, Kowloon Tong, Hong Kong.
authors.forename: Rui-Qi
authors.initials: RQ
authors.lastname: Yue
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, 7 Baptist University Road, Kowloon Tong, Hong Kong.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, 7 Baptist University Road, Kowloon Tong, Hong Kong.
authors.forename: Hing-Man
authors.initials: HM
authors.lastname: Ho
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, 7 Baptist University Road, Kowloon Tong, Hong Kong.
authors.forename: Tao
authors.initials: T
authors.lastname: Yi
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, 7 Baptist University Road, Kowloon Tong, Hong Kong. Electronic address: hbchen@hkbu.edu.hk.
authors.forename: Hu-Biao
authors.initials: HB
authors.lastname: Chen
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, 7 Baptist University Road, Kowloon Tong, Hong Kong. Electronic address: simonhan@hkbu.edu.hk.
authors.forename: Quan-Bin
authors.initials: QB
authors.lastname: Han
mesh_terms: D002850:Chromatography, Gel; D003911:Dextrans / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry*; D005936:Glucans / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D003911:Dextrans; D005936:Glucans; D011134:Polysaccharides; D000431:Ethanol
keywords: Ethanol concentration; Ethanol precipitation; Natural polysaccharides; Polysaccharide structures