| Products from cell culture consist of two major types: extracellular products and intracellular products, with different features in product separation and purification processes. In this paper, the separation and purification processes of two kinds of typical products, extracellular mildiomycin (MIL) and intracellular S-adenosyl-L -methionine (SAM), were investigated, in which, the ion-exchange separation technique was considered the core unit operation step and the procedures with high efficiency and low contamination were developed. The processes were proved successfully in both laboratory and pilot scales.Mildiomycin is an extracellular product during Streptoverticillium rimofaciens fermentation, is a novel nucleoside agro-antibiotics which shows a specific and strong inhibitory activity against fungi, especially, powdery mildews. Because of its low action dosage, excellent environmental compatibility and remarkably low toxicity to human and animals, MIL is regarded as a new kind of green biological pesticides. S-adenosyl-L -methionine is a key metabolic intermediate in vivo, which is involved in transmethylation reactions, trans-sulfuration pathway and polyamine biosynthesis, and exhibits a variety of important physiological activities. It is being administered as an important therapeutics for the treatment of various clinical disorders, such as liver diseases, osteoarthritis and depressive syndromes. SAM is a kind of intracellular product, and the addition of L -methionine as precursor can promote the accumulation of SAM in yeast cells. According to the different characteristics of MIL and SAM, it is necessary to develop specific separation and purification strategies for each product. Because both products share some common properties such as water-soluble, ionizable, low molecular weight, etc., the ion-exchange technique can be the core unit operation in the procedure.1. Separating MIL from fermentation brothAn optimized procedure was developed for MIL separation and purification from fermentation broth, which included the following main steps: pretreating fermentation broth, ion exchanged by HZ011 resin, decolored and desalted by D296 resin and 001x16 resin respectively, and further purified by HD-2 resin. By this process, high purity MIL was produced with high recovery.The distinguished features of the process are as followings: 1) The fermentation broth of MIL was pretreated by oxalic acid precipitation. The advantages of oxalic acid precipitation were not only the simultaneous removal of acidic proteins, calciumABSTRACTand magnesium ions from fermentation broth but also the enhancement of the ion-exchange capacity of MIL on cationic ion-exchange resin. In the meanwhile the precipitated acidic proteins were functioned as the filtration aid, which was favorable for easy mycelia filtration and high MIL recovery in this step; 2) According to the strong alkali property of MIL, the weak acid cationic exchange resin HZ011 was selected as the adsorbent because of its high ion-exchange capacity and easy elution of MIL. The effects of temperature, pH value, MIL concentration, flow rate and elution conditions on the ion-exchange isotherms and ion-exchange kinetics were investigated. After the optimization of operation parameters, the recovery of MIL in this step reached 94.5%; 3) Simultaneous decolorization and anionic MIL salts were performed and optimized by using a strong alkali anion exchange resin D296. The decolorization ratio and MIL recovery were as high as 97.2% and 95.4%, respectively. 4) A high degree of cross linked gel -type strong acid resin, 00116, and a weak acid cationic exchange resin specified for chromatography, HD-2, were used to remove inorganic salts and to purify MIL, respectively. The final MIL product with 95% purity was obtained.The chemical formula and structure were confirmed by elemental analysis, HPLC, UV spectrum, IR spectrum, NMR spectrums ( 13C and 'H) and Mass Spectrum. The soluble powder containing 5.5% MIL was prepared and applied to assay its indoor biological ac...
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