The Study Of Exopolysaccharides From Anoxybacillus Kamchatkensis L1in Random Hot Spring

Microbial polysaccharides mainly refer to the polysaccharide produced by most bacteria, a small amount of fungi and algae. Microbial exopolysaccharides (EPS) are useful biomolecules secreted by bacteria under specific circumstances. The diversity in chemical composition of EPS results in a variety of properties that could be widely used in food, pharmaceutical and industrial fields. Numerous studies proposed a variety of adsorbent materials for the removal of heavy metals. Among these, EPS have been recently investigated as one of key adsorbents for biosorption of heavy metals. Therefore, it is meaningful to do research on EPS from bacteria. In this study, the EPS were extracted from the medium of Anoxybacillus kamchatkensis L1. Its extraction, isolation, structure identification and biosorption capacity of heavy metal were further studied. The major results obtained in this study were as follows.Response surface method (RSM) was applied to optimize the fermentation medium components of EPS production from Anoxybacillus kamchatkensis L1, including the amount of carbon source, nitrogen source and inorganic salts. The optimum conditions of medium were obtained as follows:7.8g/L Lactose,0.45g/L (NH4)2SO4,0.24g/L KH2PO4, the yield of EPS could reach up to128.16mg/L, which was better optimized than traditional medium. DEAE Sepharose Fast Flow ion exchange column and Sephadex G-200column were used to decolor and deproteinize crude EPS from Anoxybacillus kamchatkensis L1. The obtained EPS were isolated into two components (LEPS-1and LEPS-2). Because of low yield of LEPS-1, the followed research was carried on LEPS-2. Its purity and molecular weight was determined by HPLC. From HPLC analysis, the average molecular weight of LEPS-2was about1000kD. From IR, LEPS-2was polysaccharides. From GC analysis, LEPS-2was composed of Man and Glc with molar ratio of2.91:1.30.Crude LEPS-2war used as adsorbent to treat heavy metals Zn2+and Cd2+. From FAAS analysis, pH6.0、60min are the optimal condition for metal ion removal of both. The experimental data fit well for the Langmuir and Freundlich isotherm models. The maximum sorption capacities of LEPS-2for Zn2+, Cd2+were1.41,1.95mg/g, respectively. When these two metal ions exist at the same time, the sorption capacities could reach1.38,2.28mg/g, respectively. According to IR analysis, several functional groups, including carboxyl, ether and hydroxyl groups, were involved in the sorption of Zn2+and Cd2+metal ions, and ion-exchange was an important mechanism for the sorption process.