Composition and chemical structures analysis of exopolysaccharides produced by Haloferax mediterranei

• Main Authors: Gu-Hong Lin, 林谷鴻
• Other Authors: C. Will Chen
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/76436896001805958978

碩士 === 大同大學 === 生物工程學系(所) === 98 === Extracellular polysaccharides (EPS) has been widely applied to different areas, such as food, medicine, cosmetics and biotechnology industries. The halophilic bacteria Haloferax mediterranei produces EPS with functional group of sulfate and mannose. This study use corn flour as the cheap carbon source at concentration of 15.5 g/L, under shaker flasks culture of temperature 42 ℃ and rotational speed of 180 rpm, to produce EPS. After 120 hours, the measured absorbance OD520 of cell concentration reached a maximum value of 19.9. EPS had been extracted and purified by ion-exchange chromatography on DEAE-Sepharose using a linear(0 ~ 2 M) NaCl gradient, and separated as four significant peaks (CP1, CP2, CP3, CP4) of different compositions. The overall recovery of EPS was 50 % with CP1, CP2, CP3 and CP4 of 29.6 %, 8.7 %, 4.3 % and 4.8 % recovery, respectively. Through the Fourier transform infrared spectroscopy (FTIR) analysis, CP1 ~ CP4, shown the absorption of wavelength at 1039 ~ 1233 cm-1, 1374 ~ 1418 cm-1 and 1540 ~ 1652 cm-1 with corresponding functional groups of S=O, CH bend, and－CO－NH－R, respectively. From the elemental composition analysis, CP1 ~ CP4 had sulfur content of 3.6 %, 6.3 %, 2.2 % and 2.4 % respectively. From the 1H NMR analysis, the chemical shifts of CP1 ~ CP4 focused on the range of 1.0 ~ 5.2 ppm. CP1 and CP2 shown the anomeric protons at 5.22 ppm, 4.95 ppm, 4.86 ppm , and at 5.22 ppm, 4.99 ppm, 4.90 ppm respectively. The anomeric protons of CP1 and CP2 indicated that the bonding between the monosaccharide units are in the form of one α- and two β-linkeage, therefore it is speculated that the chemical structure of CP1 and CP2 are tri-saccharides repeated units. The anomeric protons at CP3 and CP4 show four chemical shifts of 5.02 ppm, 4.56 ppm, 4.42 ppm, and 4.35 ppm, which represent one α- and three β-linkeage units, therefore it is speculated that CP3 and CP4 have chemical structure of tetra-saccharides. . This study proposes the chemical structure of tri-saccharides at CP1 and CP2, and also the structure of tetra-saccharides at CP3 and CP4.