酿酒酵母芳樟醇耐受性的工程改造

Engineering of Saccharomyces cerevisiae for improved tolerance to linalool

摘要:

【背景】芳樟醇具有特殊的香气和多种生物学活性，是食品、医药和化妆品行业的重要原料。随着合成生物学的高速发展，代谢改造微生物进行芳樟醇生物合成是当前研究的一大热点。然而在微生物的生物合成中，芳樟醇对底盘细胞的毒性是一大瓶颈问题，也是其他单萜物质生物合成的共性问题。【目的】建立合理的耐受性改造方法，以提高微生物宿主细胞对芳樟醇的耐受性。【方法】以酿酒酵母BY4741为研究对象，通过对ABC转运蛋白、活性氧调控相关酶及转录调控因子的过表达，考察它们对酿酒酵母芳樟醇耐受性的影响，并通过对酿酒酵母细胞进行定向驯化，筛选耐受性提高的酿酒酵母突变株。【结果】单独过表达ABC转运蛋白(Yor1、Snq2、Pdr5、Pdr15和Pdr18)、ROS调控相关酶(Gre2、Ctt1、Yhb1、Gpx2、Trr1、Trx2和Gsh2)及转录调控因子(Ino2、Yap1、Yap5和Stb5)并不能有效提高酿酒酵母的耐受性，但在传代适应性驯化过程中获得了两株耐受性提高的酿酒酵母突变株，将芳樟醇的致死浓度从430 mg/L提高到了645 mg/L以上。进一步通过基因组重测序分析揭示了驯化菌株突变位点。其中YBR074W、YBR172C、YHR007C和YMR275C这4个基因的突变对耐受性的提高具有重要影响。【结论】本研究通过进化工程成功提高了酿酒酵母对芳樟醇的耐受性，为今后单萜耐受性机制的研究提供了参考，为单萜的异源合成提供了优良的底盘细胞。

关键词:酿酒酵母;芳樟醇;ABC转运蛋白;活性氧;耐受性;适应性进化

Abstract:

[Background] Having special fragrance and various biological properties, linalool has become an important feedstock for food, pharmaceutical and cosmetics industries. With the development of synthetic biology, metabolic engineering of microorganisms has become an influential alternative for biosynthesis of linalool. However, the strong toxicity of linalool to host cells is a key bottleneck for microbial production of linalool and other monoterpenes. [Objective] This paper aimed to develop effective strategies for improving the tolerance of microbial host cells to linalool. [Methods] In this study, the ATP-binding cassette (ABC) transporters, reactive oxygen species (ROS)-related enzymes and transcription factors were overexpressed in Saccharomyces cerevisiae BY4741 to identify their roles in the tolerance of S. cerevisiae to linalool. In addition, adaptive laboratory evolution was adopted to obtain the S. cerevisiae strains with increased fitness towards linalool. [Results] Individual overexpression of ABC transporters (Yor1, Snq2, Pdr5, Pdr15 and Pdr18), ROS-related enzymes (Gre2, Ctt1, Yhb1, Gpx2, Trr1, Trx2 and Gsh2) and transcription factors (Ino2, Yap1, Yap5 and Stb5) in S. cerevisiae BY4741 failed to improve the tolerance of S. cerevisiae. Furthermore, S. cerevisiae with improved tolerance (lethal concentration of linalool was increased from 430 mg/L to 645 mg/L) were obtained via adaptive evolution and the SNV/InDel genes were analyzed by whole-genome resequencing. Mutations were found in YBR074W, YBR172C, YHR007C and YMR275C, which enhanced the tolerance to linalool. [Conclusion] The tolerance of S. cerevisiae to linalool was improved by evolutionary engineering, which laid a foundation for analyzing the mechanism of S. cerevisiae to tolerate monoterpenes and provided an excellent chassis cell for heterologous synthesis of monoterpenes.

Key words:Saccharomyces cerevisiae;linalool;ATP-binding cassette transporter;reactive oxygen species;tolerance;adaptive evolution