A practical method for the racemization of L-Alanine has been developed by microwave irradiation.It is economical,convenient and environmentally acceptable way to racemize L-Alanine.By single factor cyclical method,the factors influencing the racemization were investigated.Finally,by optimization of response surface methodology,the whole process of racemization can be completed within 1 h in a medium of 1.2mol/L NaOH under reflux conditions for in the presence of 0.14 molar equivalent of Salicylaldehyde by using 560W microwave irradiation.It is also showed that the reaction rates is speed up with the increase of the power of microwave.The mechanism of the racemization was discussed.

An enzymatic method for the optical resolution of DL-theanine by aminoacylases from Cunnighamella echinulata 9980 was developed.The optimum temperature,pH and substrate concentration were: 50℃,pH7.0,and 0.5mol/L N-Ac-DL-theanine.The conversion rate against N-Ac-L-theanine was 92%.Productions were purified on JK008 ion exchange resin.The yield of L-theanine was 84.3%,[α]2D5 =8.1(c=2,H2O),complied with JP2000。

Taking DL-phenylalanine as substrate,D-phenylalanine was obtained via using phenylalaine deaminase from Bacillus megaterium AS1.127,which has the specific oxidative deamination ability for L-phenylalanine.The factors affecting the enzymatic reaction were discussed and the optimum conditions were obtained.The results showed that the optimum temperature was 40℃ and pH was 5.8.The presence of 0.2 mol/L phosphate buffer solution resulted in an enhancement of the enzyme activity.The conversion rate was remarkably enhanced in the presence of 0.2% Tween-80 and 10~(-5) mol/L K~+.The conversion rate was related with the concentration of both the substrate and the mycelia.When the concentration of the substrate DL-phenylalanine was 0.09 mol/L,the mycelia was 0.03 g/mL and the reaction time was 18 h,the yield was more than 98%.D-phenylalanine was obtained after decoloring of the enzymic reaction solution,concentrating and crystallizing,and its optical purity was higher than 95%.

选育出一株具有较高苯丙氨酸脱氨酶活性的菌株巨大芽孢杆菌AS1.127-NJU10.考察了该菌的发酵产酶条件,结果表明:蔗糖为最佳碳源、酵母浸膏和NH4Cl组成最佳氮源,其质量浓度分别为:ρ(蔗糖)=20g/L,ρ(酵母浸膏)=2g/L和ρ(NH4Cl)=10g/L;发酵培养基最适pH=6.5,培养温度为37℃;诱导物ρ(L-苯丙氨酸)=1g/L时,酶活最高达1 070 U.同时对苯丙氨酸脱氨酶的性质进行了研究,结果表明:该酶最适pH=5.8,最适温度为40℃,反应液中添加ψ(吐温-80)=0.2%和c(K+)=10-5mol/L能明显提高酶活.

An enzymatic method for the production of D-phenylalanine by aminoacylases from Cunnighamella echinulata 9980 was developed. The optimum conditions were as follows: 0.2 mol/L N-Ac-DL-phenylalanine(including Co 2+ 5×10 -4mol/L),0.04 g/mL mycelia, pH 7.0. After 24 h incubation at 50 ℃,the conversion rate against N-Ac-L-phenylalanine was higher than 90%. L-phenylalanine and N-Ac-D-phenylalanine were separated and purified on JK008 ion exchange resin. N-Ac-D-phenylalanine was hydrolyzed by 6 mol/L hydrochloric acid for 4 h, then D-phenylalanine crystal was obtained. D-Phe[α] 20_D=+34.4°(H_2O).

介绍了微波促L-苯丙氨酸消旋反应是一种新的可适合于工业化的生产方法,具有对环境友好的优点.使用微波作为热源不仅可加速反应和节约能源,也可提高反应的收率和产品的纯度.本方法确定了在微波辐射下,以1.0 mol/L氢氧化钠水溶液替代低级脂肪酸作为反应溶剂,用物质的量比为0.10的水杨醛为催化剂,L-苯丙氨酸可以快速消旋;在此条件下,消旋反应随微波辐射功率的提高而加快,在66%输出功率下反应已接近最大反应速率.从实验中得出微波促L-苯丙氨酸消旋的反应是一级不可逆反应.考察了此消旋反应的影响因素,同时讨论了微波作用下L-苯丙氨酸的消旋反应机理.

L-Alanyl-L-glutamine(Dipeptiven) was prepared in 10 t/a pilot-plant-scale by using phthalyl method and mixed anhydride method.The result showed that the optimal solvent used to dissolve N-Pht-L-alanine was ethyl acetate,the optimal temperature was 0 ℃,and the molar ratio of N-Pht-L-alanine to L-glutamine was 1∶1.The overall molar yield was 34.4% based on L-alanine.w(L-alanyl-L-glutamine(Dipeptiven))=98.6%.