Abstract

Hydroxytyrosol (4-(2-hydroxyethyl)-1,2-benzenediol) is the most known bioactive compound from the plant Olea europaea (olive tree). To date, few biocatalysis processes allowing efficient production of hydroxytyrosol from potential substrates including, tyrosol (2-(4-hydroxy) phenyl ethanol) and tyrosine have been reported. In this paper, we report for a Gram-positive bacterium that produces hydroxytyrosol via conversion of tyrosol and/or L-tyrosine, identified as a Rhodococcus pyridinivorans based on phenotypic characteristics and 16S rDNA sequence, and designated R. pyridinivorans strain 3HYL DSM109178. Interestingly, strain 3HYL shows an outstanding production of hydroxytyrosol from tyrosol up to 16.4 ± 0.23 mmol/L with high kinetic parameters exceeding the reported values. However, a slight downstream metabolism of the product is assigned to the wild-type strain during the stationary phase of growth. The plasmid-cured strain was obtained using random chemical mutagenesis, designated R. pyridinivorans 3HYL-AO, and was able to produce hydroxytyrosol, with yields up to 21.75 ± 0.34 mmol/L. Moreover, the plasmid-cured strain exhibited a significant reduction in the transformation to its acetic acid forms compared to the wild-type strain as depicted by HPLC analysis. Comparison of kinetic data of the bioconversion/accumulation process between the wild type and mutant strain, in the presence and absence of L-tyrosine, and thus suggesting the occurrence of an upstream pathway for synthesis of tyrosol via (L)-tyrosine.

摘要

羟基酪醇（4-（2-羟乙基）-1,2-苯二醇）是来自植物油橄榄（橄榄树）的最著名的生物活性化合物。迄今为止，很少有生物催化过程能够从包括酪醇（2-（4-羟基）苯基乙醇）和酪氨酸在内的潜在底物有效生产羟基酪醇。在本文中，我们报告了一种通过酪醇和/或 L-酪氨酸转化产生羟基酪醇的革兰氏阳性细菌，根据表型特征和 16S rDNA 序列鉴定为嗜吡啶红球菌，并命名为R. pyridinivorans菌株 3HYL DSM109178。有趣的是，菌株 3HYL 显示出从酪醇到 16.4 ± 0.23 mmol/L 的出色羟基酪醇产量，其高动力学参数超过了报道的值。然而，在生长的稳定阶段，产物的轻微下游代谢被分配给野生型菌株。使用随机化学诱变获得质粒治愈的菌株，命名为R. pyridinivorans3HYL-AO，并能够生产羟基酪醇，产率高达 21.75 ± 0.34 mmol/L。此外，如 HPLC 分析所示，与野生型菌株相比，质粒治愈的菌株在向其乙酸形式的转化方面表现出显着减少。在存在和不存在 L-酪氨酸的情况下，野生型和突变株之间生物转化/积累过程的动力学数据的比较，从而表明存在通过 (L)-酪氨酸合成酪醇的上游途径。