醛代表了一种通用且受欢迎的调味物质。通过用α-双加氧酶途径的两种酶转化脂肪酸,开发了对气味活性醛的生物催化途径。在大肠杆菌中异源表达了源自下热带Crocospaera的重组酶α-双加氧酶(α-DOX)和来自哈氏弧菌的脂肪醛脱氢酶(FALDH),纯化,并应用于偶联(串联)重复反应。该概念在反应循环次数和产率方面进行了优化。达到高达5个循环和高达26%的醛产率。之后,该方法以沙棘果肉油为原料,用于基于复杂醛混合物的酶催化生产调味/香料成分。沙棘果肉油中最丰富的脂肪酸,即棕榈,棕榈油,油酸,和亚油酸,用作进一步生物转化实验的底物。鉴定了各种醛,半量化,并通过顶空-固相微萃取-气相色谱-质谱-嗅觉测定法(HS-SPME-GC-MS-O)进行感官表征。不饱和醛在双键位置方面的结构验证是通过其Paterno-Büchi(PB)光产物的多维高分辨率质谱实验进行的。保留指数和气味印象(Z,Z)-5,8-十四碳二烯醛(Z,Z)-6,9-十五碳二烯醛,(Z)-8-十五烯醛,(Z)-4-十三进制,(Z)-6-十五烯醛,首次测定(Z)-8-十七烯醛。关键点:•Csα-DOX和VhFALDH的偶联反应产生链缩短的脂肪醛。•首次描述了几种Z-不饱和脂肪醛的气味。•从天然来源工业生产基于醛的气味剂的潜力。
Aldehydes represent a versatile and favored class of flavoring substances. A biocatalytic access to odor-active aldehydes was developed by conversion of fatty acids with two enzymes of the α-dioxygenase pathway. The recombinant enzymes α-dioxygenase (α-DOX) originating from Crocosphaera subtropica and fatty aldehyde dehydrogenase (FALDH) from Vibrio harveyi were heterologously expressed in E. coli, purified, and applied in a coupled (tandem) repetitive reaction. The concept was optimized in terms of number of reaction cycles and production yields. Up to five cycles and aldehyde yields of up to 26% were achieved. Afterward, the approach was applied to sea buckthorn pulp oil as raw material for the enzyme catalyzed production of flavoring/fragrance ingredients based on complex aldehyde mixtures. The most abundant fatty acids in sea buckthorn pulp oil, namely palmitic, palmitoleic, oleic, and linoleic acid, were used as substrates for further biotransformation experiments. Various aldehydes were identified, semi-quantified, and sensorially characterized by means of headspace-solid phase microextraction-gas chromatography-mass spectrometry-olfactometry (HS-SPME-GC-MS-O). Structural validation of unsaturated aldehydes in terms of double-bond positions was performed by multidimensional high-resolution mass spectrometry experiments of their Paternò-Büchi (PB) photoproducts. Retention indices and odor impressions of inter alia (Z,Z)-5,8-tetradecadienal (Z,Z)-6,9-pentadecadienal, (Z)-8-pentadecenal, (Z)-4-tridecenal, (Z)-6-pentadecenal, and (Z)-8-heptadecenal were determined for the first time. KEY POINTS: • Coupled reaction of Csα-DOX and VhFALDH yields chain-shortened fatty aldehydes. • Odors of several Z-unsaturated fatty aldehydes are described for the first time. • Potential for industrial production of aldehyde-based odorants from natural sources.