Abstract Vanillin is a value added compound used in wide range of areas including food, beverage, fragrance and pharmaceutical. It can be produced by reduction of vanillic acid, a by-product in lignin degradation processes or a competing component in the metabolic pathways in biological vanillin production. The reduction process is energetically disadvantageous due to the high activation energy in the reaction coordinates, but can be overcome by an enzymatic strategy using carboxylic acid reductases (CARs). In this study, fourteen CARs heterologously expressed in Escherichia coli were tested for vanillic acid reduction, of which a CAR from Mycobacterium abscessus B1MLD7 gene, as a result, was selected for the highest activity. The selected CAR exhibited 8.6-fold higher in vitro activity than that of the CAR from Nocardia iowensis Q6RKB1, previously reported to have the highest activity in vanillic acid reduction. The effect of substrate concentration and reducing power supply on the biocatalytic reaction has been investigated to enhance the yield while minimizing the by-product formation, resulting in 2.86 g L−1 of vanillin production in the whole cell biocatalytic reaction. The sequential and structural analyses of the enzyme with molecular modeling also have been carried out to discuss the catalytic characteristics of the enzyme.

中文翻译：

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一种来自脓肿分枝杆菌的高活性羧酸还原酶，用于将香草酸生物催化还原为香草醛

摘要 香兰素是一种增值化合物，广泛应用于食品、饮料、香料和制药等领域。它可以通过还原香草酸、木质素降解过程中的副产品或生物香草醛生产中代谢途径中的竞争成分来生产。由于反应坐标中的高活化能，还原过程在能量上是不利的，但可以通过使用羧酸还原酶 (CAR) 的酶促策略来克服。在这项研究中，对在大肠杆菌中异源表达的 14 种 CAR 进行了香草酸还原测试，结果选择了来自脓肿分枝杆菌 B1MLD7 基因的 CAR 的活性最高。所选 CAR 的体外活性比来自 Nocardia iowensis Q6RKB1 的 CAR 高 8.6 倍，先前报道在香草酸还原中具有最高活性。研究了底物浓度和降低电源对生物催化反应的影响，以提高产率，同时最大限度地减少副产物的形成，在全细胞生物催化反应中产生 2.86 g L-1 香草醛。还通过分子模型对酶进行了序列和结构分析，以讨论酶的催化特性。