Separation Of 5-Aminolevulinic Acid From Recombinant E.coli Fermentation Broth By Ion Exchange

5-aminolevulinic acid (ALA) is the common precursor of tetrapyrroles. It exists in many organisms and has wide use in agriculture and medicine. Using recombinant E. coli to produce high-yield ALA is a new and promising technology. However, there are very few researches about separating ALA from fermentation broth. So this dissertation will pay attention to the process of separating ALA from fermentation broth.ALA belongs to the class of amino ketones. Its stability should be considered in the process of separation. ALA is stable under low pH and low temperature.Pigments bring much trouble in purifying ALA and regenerating the resins. The thesis investigated an effective technology to decolorize the fermentation broth. Active carbon powder HC-772 was selected and the decoloring conditions were optimized as follows: pH5.0, HC-772 dosage 2%-3%, decoloring time 15-20min.Under these conditions, the decoloring and recovery efficiency achieved 95.2% and 91.6% respectively.ALA is expected to be separated by ion exchange resins. A strong cation exchange resin 001×7 was selected from 15 different resins. It shows high static exchange capability and good dynamic character. The initial adsorption pH was determined to be 5.0 by investigating breakthrough curves and adsorption isotherm curves. The approximate purity of ALA in the solution was measured by HPLC at 210nm. The ion exchange conditions were determined as follows: adsorption flow rate 2BV·h^-1, elution flow rate 1.5 BV·h^-1, concentration of HCl solution 1.5M. Under these conditions, ALA was concentrated to 30.97g·L^-1 from 5.57g·L^-1; HPLC purity reached 51.78%; the recovery efficiency was 85.52%.This separation process was scaled up by a bigger ion exchange column (Φ34×520mm) and the primary separation purpose was achieved.Method of further purifying crude ALA was investigated. Ethanol could remove the impurities of crude ALA tremendously. The conditions to refine crude ALA were confirmed: solving the crude product by methanol; precipitating ALA·HCl by ether. HPLC purity of the product was increased from 36.86% to 90.16%.