Institute of Interfacial Process Engineering and Plasma Technology IGVP, University of Stuttgart, 70569 Stuttgart, Germany.
Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, 70569 Stuttgart, Germany.
J Ind Microbiol Biotechnol. 2021 Aug 24;48(7-8). doi: 10.1093/jimb/kuab042.
Mannosylerythritol lipids (MELs) are glycolipid biosurfactants produced by fungi of the Ustilaginaceae family in the presence of hydrophobic carbon sources like plant oils. In the present study, we investigated the structural composition of MELs produced from castor oil using seven different microorganisms and compared them to MEL structures resulting from other plant oils. Castor oil is an industrially relevant plant oil that presents as an alternative to currently employed edible plant oils like rapeseed or soybean oil. The main fatty acid in castor oil is the mono-hydroxylated ricinoleic acid, providing the possibility to produce novel MEL structures with interesting features. Analysis of the produced MELs from castor oil by different chromatographic and mass spectrometry techniques revealed that all seven microorganisms were generally able to integrate hydroxylated fatty acids into the MEL molecule, although at varying degrees. These novel MELs containing a hydroxy fatty acid (4-O-[2'-O-alka(e)noyl-3'-O-hydroxyalka(e)noyl-4'/6'-O-acetyl-β-D-mannopyranosyl]-erythritol) were more hydrophilic than conventional MEL and therefore showed a different elution behavior in chromatography. Large shares of novel hydroxy MELs (around 50% of total MELs) were found for the two MEL-B/C producing species Ustilago siamensis and Ustilago shanxiensis, but also for the MEL-A/B/C producer Moesziomyces aphidis (around 25%). In addition, tri-acylated hydroxylated MELs with a third long-chain fatty acid esterified to the free hydroxyl group of the hydroxy fatty acid were identified for some species. Overall, production of MEL from castor oil with the investigated organisms provided a complex mixture of various novel MEL structures that can be exploited for further research.
甘露糖基赤藓糖醇脂质（MEL）是一种糖脂生物表面活性剂，由担子菌门真菌在存在疏水性碳源（如植物油脂）的情况下产生。在本研究中，我们研究了使用七种不同微生物从蓖麻油中生产的 MEL 的结构组成，并将其与其他植物油脂产生的 MEL 结构进行了比较。蓖麻油是一种工业相关的植物油脂，可替代目前使用的食用植物油脂，如油菜籽油或大豆油。蓖麻油的主要脂肪酸是单羟基化的蓖麻酸，为生产具有有趣特性的新型 MEL 结构提供了可能性。通过不同的色谱和质谱技术分析从蓖麻油中生产的 MEL 表明，所有七种微生物通常都能够将羟基化脂肪酸整合到 MEL 分子中，尽管程度不同。这些含有羟基脂肪酸（4-O-[2'-O-酰基-3'-O-羟基酰基-4'/6'-O-乙酰-β-D-甘露吡喃糖基]-赤藓糖醇）的新型 MEL 比传统 MEL 更亲水，因此在色谱中表现出不同的洗脱行为。新型羟基 MEL 的大量份额（约占总 MEL 的 50%）在两种 MEL-B/C 产生菌蕈状枝孢菌和山西枝孢菌中发现，但在 MEL-A/B/C 产生菌蚜虫枝孢菌中也发现了（约 25%）。此外，还鉴定了一些物种中具有第三个长链脂肪酸酯基化到羟基脂肪酸游离羟基上的三酰化羟基 MEL。总的来说，用所研究的微生物从蓖麻油生产 MEL 提供了各种新型 MEL 结构的复杂混合物，可以进一步研究利用。
