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酶转化法是生产β-丙氨酸的重要途径,但单一酶法转化存在底物价格较高的问题。通过构建双酶催化体系制备β-丙氨酸,即将来源于大肠杆菌的天冬氨酸酶(AspA)和来源于谷氨酸棒杆菌的L-天冬氨酸α-脱羧酶(PanD)偶联,以富马酸和氨为底物进行酶促反应合成β-丙氨酸。催化反应中AspA与PanD的最适加酶比例为1∶80,其中AspA的浓度为10μg/mL,转化温度为37℃,pH为7.0;浓度为100 mmol/L的富马酸可在8 h内被完全转化,转化率为100%,摩尔产率为90.9%,β-丙氨酸的产量为90 mmol/L,约为7 g/L;浓度为200 mmol/L的富马酸在反应8 h后,体系中β-丙氨酸的产量为126 mmol/L,约合9.8 g/L,继续延长反应时间,转化率并没有明显提高。根据该研究提出的双酶偶联转化工艺可将价格低廉的富马酸一步转化为具有高附加值的β-丙氨酸。
Enzyme conversion is an important way to produce β-alanine, but there is a problem of higher substrate price in single enzyme transformation. Β-alanine was prepared by constructing a double-enzyme catalytic system, that is, the AspA derived from Escherichia coli and the L-aspartate α-decarboxylase (PanD) even derived from Corynebacterium glutamicum Associated with fumaric acid and ammonia as substrates for enzymatic synthesis of β-alanine. The optimal ratio of AspA to PanD was 1:80 in the catalytic reaction, in which the concentration of AspA was 10μg / mL, the temperature of transformation was 37 ℃ and the pH was 7.0. When the concentration of AspA was 100 mmol / L, Was completely converted, the conversion rate was 100%, the molar yield was 90.9%, the yield of β-alanine was 90 mmol / L, which was about 7 g / L; the concentration of 200 mmol / L of fumaric acid in the reaction After 8 h, the yield of β-alanine in the system was 126 mmol / L, which was about 9.8 g / L. The reaction time was prolonged without any significant increase in conversion. According to the double enzymatic coupling conversion process proposed in this study, low-cost fumaric acid can be transformed into β-alanine with high added value in one step.