双酶偶联转化富马酸制备β-丙氨酸的工艺的建立与优化

Biocatalytic access to β-alanine by a two-enzyme cascade synthesis

摘要:

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10 μg/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。

Abstract:

Enzymatic synthesis is an important way to produce β-alanine, but the biological method is expensive generally because of the high price of substrate. In this paper, a two-step enzymatic cascade system was developed, combining L-aspartase from Escherichia coli DH5α and L-aspartate α-decarboxylase from Corynebacterium glutamicum. This system catalyzes Fumarate and ammonia to β-alanine. The optimal ratio of AspA and PanD was 1:80 (W/W), and the concentration of AspA was 10 μg/mL, at 37 ℃ and pH 7.0. When the concentration of Fumarate was 100 mmol/L, the reaction reached its equilibrium after 8 h, and the yield of β-alanine was 90 mmol/L (7 g/L). The yield of β-alanine can reach 126 mmol/L (9.8 g/L) when the concentration of Fumarate increased to 200 mmol/L. Extending reaction time, the conversion rate did not change obviously. Using this two-step enzymatic cascade system, β-alanine from cheaper substrate Fumarate can be obtained.