Separation And Purification Of L-arginine In The Corynebacteruim Crenatum Fermentation Broth

L-arginine,a kind of semi-essential aino acid,the most alkaline natural amino acid,has been widely used in food,pharmaceuticals and chemical industry.In the passed years,production of L-arginine by fermentation has been largely improved oweing to the researcher`s efforts.However,the seperation and purification process of L-arginine from fermetation in our country is still poor,resulting in the lower quality of L-arginine product than that of other countries,such as low stability of quality,nonuniform size of crystal and low purity.Consequently,it is far more important to get a more efficient process to recover the L-arginine from fermentation broth,so that we can improve the competiveness of L-arginine product prodeced by our country.In this study,the recovery process of L-arginine from fermentation broth was systematicaly studied for the achievement of high efficent recovery process.The cells in fermentation broth was removed by ceramic membrane filtration,the concentraton of L-arginine in filtrate was 55.67 g?L^-1,the purity and recovery of L-arginine were 64.7% and 98.3%,respectively.Resin D155 was proved to be the best resin to absorb L-arginine in fermentation according to the static ion exchange experiment.The adsorption isotherms of L-arginine absorbed to D155 being fairly explained by the Langmuir model.The natured pH of fermentation broth?pH 6.7-6.8?can gives both high capacity and transparency of desorption solution.Consequently,the filtrate can be used for ion exchange without adjusting pH.Thermomechnical analysis of ion exchange showed that the adsorption of L-arginine to D155 was spontaneous and exothermic,higher temperature was not good for the adsorption.Kinetics analysis showed that the process is always controlled by intra-particle diffusion of L-arginine both in L-arginine solution and fermentation broth.Consequently,the resin partical size should be reduced properly.In the D155 fixed bed operation the best,the optimal flow rate for feeding was 6 m L?min-1,the optimal concentration of eluent was 2 mol?L^-1 ammonia solution,the optimal flow rate of elution was 6m L?min-1,the results show that Thomas and Yoon-Nelson models can give satisfactory prediction of breakthrough curve at all conditions studied.The resin should be regenerated after being used for 6 times during the reuse of D155.The continuous ion exchange system consist of 30 columns was designed,and the optimal flow rates of adsorption zone,rinsing zone after adsorption,desorption zone,rinsing zone after desorption,excluding water zone are 6,6,5,10,3 mL?min-1,respectively.The designed continuous ion exchange system can operate steady at the optimal flow rates,and the outlet concentration of each zone changed periodically.Compared with the fixed bed operation,61% water consumption and 68% alkali consumption can be reduced,the resin utilization has been improved for 33% by using the continuous ion exchange system.The purity and recovery of L-arginine were 92.5% and 98.8%,respectively.The optimal temperature addition of activated carbon decoloration time were 50?,0.6%,45 min,respectively.After decoloration for two times,the transparency of the solution,the purity and recovery of L-arginine were 97%,93.2%,97.1%,respectively.For anion exchange removing the impurity in solution after removel of ammonia,the best anion exchange resin was 711,the optimal flow rate was 4 BV?h^-1,the break through volume was 3.9 BV.After anion exchange using resin 711,the transparency of the solution,the purity and recovery of L-arginine were 97%,98.5%,97.8%,respectively.According to the comparision of the decoloration process with activated carbon and anion exchange,the resin 711 was the better choice to remove the color and other impurity in the solution after removal of ammonia.The solubility of L-arginine was increased as the increase of temperature and decreased as the increase of the percentage of ethanol in ethanol-water system,and the solubility equation of L-arginne in aqueous solution and ethanol-water system was obtained.The metastable zone was increased as the increase of cooling rate and decreased as the increase of agitation speed.The optimal process for crystallization of L-arginine by cooling process was initial temperature 60?,end temperature 10?,initial degree of supersaturation 1.15,addition of crystal seed 1%,crystal growing time 30 min,agitation speed 250 rpm,cooling rate 6??h^-1,the L-arginine crystal obtained six prisms,the main partical size was 1024 ?m.The L-arginine had been recovered from fermentation broth using the process obtained in this study with the purity and recovery of 99.2% and 82.5%,and the quality of the product met the standard in The People's Republic of China Pharmacopoeia Standard 2010 edition.