Studies On The Fermentation And Extraction Of L-Arginine

L-Arginine has many important physiological functions,including lowering blood pressure,regulating blood sugar and enhancing human immunity,which is mainly from food protein,endogenous synthesis and body protein.The main content of this paper is based on the His-deficient strain Yellow Bacillus.A His-deficient strain with high arginine production was obtained by rejuvenation and screening.An arginine analog sulfamethoxazole-resistant high resistant strain was obtained by ARTP mutagenesis.The feedback inhibition of metabolism by arginine accumulation is relieved,and the sugar inhibition effect of high concentration glucose on the strain is relieved.Through the research on the fermentation medium and culture conditions of the shake flask,the necessary preconditions for the industrial production and fermentation of arginine are improved.The fermentation tank culture conditions are further optimized by using a fermenter to control the glucose concentration of the fermentation substrate.Thereby,the arginine fermentation is stepwise amplified to carry out fermentation verification and optimization,and the L-arginine yield and the glucose conversion rate are improved.The decolorization process and ion exchange process were optimized during the separation and purification of L-arginine,and the purity and yield of the product after concentration and crystallization were analyzed,and the purification process of L-arginine fermentation solution was preliminarily determined.1.The existing strain of the laboratory produces L-arginine with a capacity of 8.3 g/L.The strain was subjected to nitrosoguanidine mutagenesis treatment to obtain a strain numbered NTG-19,which produced L-arginine of 10.4 g/L and an acid-producing ability of 25%.Based on this strain,ARTP mutagenesis was further used to obtain an L-arginine strain ARTP-27.The L-arginine concentration reached 12.7 g/L without acid optimization.It is 53%higher than the original strain.2.The basal medium was optimized using the ARTP-27 strain.The nitrogen source and carbon source in the medium are replaced by cheap corn syrup and starch hydrolyzed sugar.The optimum medium composition for shake flask fermentation was determined as follows:starch hydrolyzed sugar 100 g/L,corn syrup 15 g/L,KP,PO4 I g/L,MgSO4 0.5 g/L,NH4SO4 5 g/L,Urea 3 g/L,Mn SO4 0.02 g/L,Fe SO4 0.02 g/L,CaCO3 50 g/L.Determine the optimal culture conditions for the shake flask fermentation:the initial pH is 7.0,the rotary shaker rotation speed is 220 rpm or the swing shaker rotation speed is 90 rpm,and the 500 mL triangular flask liquid volume is 25 mL.The optimized L-arginine strain ARTP-27 produced arginine with a capacity of 15.3 g/L,and the acid production capacity was improved by 20.5%.3.The fermentation was carried out in a 5 L fermentor,and the concentration of L-Arg produced by the fermentation was increased to 23.9 g/L at a pH of 7.By optimizing the 5L fermenter fed-batch process,the concentration of L-arginine in the fermentation broth is effectively increased.At the same time,different continuous flow and feed were compared,and under the condition of controlling different glucose concentrations,the optimal flow and feed feeding scheme was optimized.When the glucose concentration was controlled at 20-30 g/L,the acid content of the strain was the highest,and the L-arginine content reached 41.5 g/L.The fermentation tank culture was expanded to 20L,200L and 2m3 tons of scale experiments,and the highest concentration of L-arginine was obtained in a 200L fermenter,with a maximum of 45.8g/L.Also in the 2m3 fermenter experiment,the small test results were well reproduced,and the final L-arginine concentration was 42.2g/L.4.The L-arginine in the fermentation broth is separated and purified.The optimum activated carbon decolorization process conditions were determined.The amount of activated carbon added was 0.8%(m/v),the decolorization temperature was 50 ℃,and the pH was about 7.0.It was confirmed that a weakly acidic cation resin and a strong basic anion exchange resin were used.When the weakly acidic cation resin was eluted with 2.0 mol/L aqueous ammonia,the yield of L-arginine was 97.88%.The 711 type strong basic anion exchange resin can further remove all anions and some soluble proteins and pigments,and the yield is 99.2%.The L-arginine product was obtained by concentrated crystallization,and the L-arginine purity was 98.58%on average.According to the results,the purification process of L-arginine fermentation broth was designed.The total yield of L-arginine is greater than 80.97%throughout the extraction protocol.