BACKGROUND The phenylbutanoid 4-(4-hydroxyphenyl)butan-2-one, commonly known as raspberry ketone, is responsible for the typical scent and flavor of ripe raspberries. Chemical production of nature-identical raspberry ketone is well established as this compound is frequently used to flavor food, beverages and perfumes. However, high demand for natural raspberry ketone, but low natural abundance in raspberries, render raspberry ketone one of the most expensive natural flavoring components. RESULTS In this study, Corynebacterium glutamicum was engineered for the microbial synthesis of the character impact compound raspberry ketone from supplemented p-coumaric acid. In this context, the NADPH-dependent curcumin/dihydrocurcumin reductase CurA from Escherichia coli was employed to catalyze the final step of raspberry ketone synthesis as it provides a hitherto unknown benzalacetone reductase activity. In combination with a 4-coumarate: CoA ligase from parsley (Petroselinum crispum) and a monofunctional benzalacetone synthase from Chinese rhubarb (Rheum palmatum), CurA constitutes the synthetic pathway for raspberry ketone synthesis in C. glutamicum. The resulting strain accumulated up to 99.8 mg/L (0.61 mM) raspberry ketone. In addition, supplementation of other phenylpropanoids allowed for the synthesis of two other naturally-occurring and flavoring phenylbutanoids, zingerone (70 mg/L, 0.36 mM) and benzylacetone (10.5 mg/L, 0.07 mM). CONCLUSION The aromatic product portfolio of C. glutamicum was extended towards the synthesis of the flavoring phenylbutanoids raspberry ketone, zingerone and benzylacetone. Key to success was the identification of CurA from E. coli having a benzalacetone reductase activity. We believe, that the constructed C. glutamicum strain represents a versatile platform for the production of natural flavoring phenylbutanoids at larger scale.

中文翻译：

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用谷氨酸棒杆菌（Corynebacterium glutamicum）合成具有特征性影响的复合覆盆子酮和其他具有生物技术意义的调味性苯基丁酮。

背景技术通常被称为覆盆子酮的苯基丁酮4-（4-羟基苯基）丁-2-酮负责成熟覆盆子的典型气味和风味。与自然界相同的覆盆子酮的化学生产已得到很好的确立，因为该化合物经常用于调味食品，饮料和香水。然而，对天然树莓酮的高需求，但是在树莓中的天然丰富度低，使得树莓酮成为最昂贵的天然调味成分之一。结果在这项研究中，谷氨酸棒状杆菌被设计用于从补充的对香豆酸中微生物合成特征性影响化合物覆盆子酮。在这种情况下，来自大肠杆菌的NADPH依赖性姜黄素/二氢姜黄素还原酶CurA被用于催化树莓酮合成的最后一步，因为它提供了迄今未知的苯并丙酮还原酶活性。与欧芹的4-香豆酸酯：CoA连接酶（Petroselinum crispum）和大黄的单功能苯甲丙酮合酶（大黄）共同构成谷氨酸棒杆菌中覆盆子酮合成的合成途径。产生的菌株积累了高达99.8 mg / L（0.61 mM）的覆盆子酮。另外，补充其他苯基丙醇允许合成另外两种天然存在和调味的苯基丁醇，姜油酮（70 mg / L，0.36 mM）和苄基丙酮（10.5 mg / L，0.07 mM）。结论C的芳族产品组合。谷氨酸被扩展用于合成风味的苯丁酮，覆盆子酮，姜油酮和苄基丙酮。成功的关键是从大肠杆菌中鉴定具有苯扎丙酮还原酶活性的CurA。我们相信，所构建的谷氨酸棒杆菌菌株代表了用于大规模生产天然调味苯基丁酮的通用平台。