Separation And Purification Of L-tryptophan From The Fermentation Broth

ObjectiveIn this study, the separation and purification of L-tryptophan were studied systematically, in order to increase the recovery efficiency of L-tryptophan from the fermentation broth.Methods1. The adequate resin was selected from 12 resins through static adsorption and elution experiments.2. The adequate decoloration resin was selected from 6 decoloration resins and activated carbon was screened through dynamic decoloration experiments.3. The conditions for adsorption,elution and decoloration were optimized through both static and dynamic experiments.4. The optimal crystallization condition of recovered L-tryptophan were obtained through the orthogonally designed experiment.Results1. Based on static adsorption and elution experiments, the highest adsorption and elution efficiency of L-tryptophan on 001×7 cation exchange resin was obtained.2. By static adsorption experiments, the effects of temperature, pH value, L-tryptophan concentration on adsorbed amount of 001×7 cation exchange resin were investigated. Results showed that the adsorption capacity was increased with increase of L-tryptophan concentration, but the adsorption efficiency was decreased. The optimal velocity was 1.0ml/min in dynamic adsorption experiment. 3. Through static and dynamic desorption experiments, the optimal NH3 concentration for elution was 2.0mol/L and the optimal velocity was 0.5ml/min.4. Based on dynamic decoloration experiment, the highest adsorption capacity of coloring materials and the lowest adsorption capacity of L-tryptophan on 315 anion exchange resin was obtained.5. In static decoloration experiments, the adsorption capacity was increased with increasing temperature.The optimal pH was 4～5. In dynamic decoloration experiment, the optimal velocity was 1.0ml/min.6. In the orthogonally desighed experiment, the optimal crystallization conditions were as following: L-tryptophan concentration:3.5%; temperature:4℃; final alcohol concentration: 10%.7. Through the separation and purification of L-tryptophan, the total recovery rate is 73.0% and purity is 98.1%.ConclusionThe optimal separation and purification conditions for L-tryptophan extraction from the fermentation broth were as following: using 001×7 cation exchange resin to adsorb, 2mol/L NH₃ to elute, D315 anion exchange resin to decolorate, and finally the extracted L-tryptophan was concentrated and crystallized. The total recovery rate is 73.0% and purity is 98.1%.