Department of Microbiology and Biotechnology Centre, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, India.
Department of Microbiology and Biotechnology Centre, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2022 Nov 15;281:121613. doi: 10.1016/j.saa.2022.121613. Epub 2022 Jul 16.
Microalgae are a rich source of carotenoids with enhanced yields during biotic or abiotic stresses, which often impose survival challenges on the cells. Using a non-invasive pigment profiling approach with micro-Raman spectroscopy, we have analyzed the effect of salinity stress on carotenoids in autotrophic Chlamydomonas reinhardtii. Raman spectral analysis of ν(C = C) mode indicates an increase in the carotenoids with lower conjugation length (lutein and zeaxanthin) compared to β-carotene, as the function of culture age and salinity stress, but especially when salinity stress was imposed in two-stage mode (stress imposed on 2nd day, D2_100, and 4th day, D4_100, during exponential phase). Population-scale heterogeneities in carotenoid Raman mode peak center, quantified with heterogeneity index (HI), were highest during the stationary phase of the cultures and under salinity stress. Although the Raman signal was obtained from a randomly selected small focal volume in the cell, a decrease in chlorophyll Raman mode intensities with age and salinity stress was well corroborated by single-cell population fraction measurements by microscopy. Raman intensity fluctuations (I) were high for both chlorophyll and carotenoid modes under salinity stress, which can arise due to variations in chlorophyll/carotenoid content and composition, or conformational changes in the pigments in C. reinhardtii cells. Interestingly, in all growth conditions, chlorophyll a Raman mode intensity was found to show a high correlation to that of β-carotene, pointing out a high degree of cooperativity in the light-harvesting complex pigments even during salinity stress. Thus, we demonstrate the usefulness of non-invasive pigment profiling with micro-Raman spectroscopy for developing an optimization for salinity stress conditions for high biomass yield and proper harvest time to obtain carotenoids with desired chemical composition.
微藻是类胡萝卜素的丰富来源，在生物或非生物胁迫下产量增加，这往往对细胞造成生存挑战。我们使用微拉曼光谱的非侵入性色素分析方法，分析了盐胁迫对自养小球藻中类胡萝卜素的影响。ν(C=C)模式的拉曼光谱分析表明，与β-胡萝卜素相比，共轭长度较低的类胡萝卜素（叶黄素和玉米黄质）随着培养年龄和盐胁迫的增加而增加，但当盐胁迫以两阶段模式施加时（在指数期的第 2 天，D2_100 和第 4 天，D4_100 施加胁迫），尤其如此。用异质性指数（HI）量化的类胡萝卜素拉曼模式峰中心的种群尺度不均匀性在培养物的静止期和盐胁迫下最高。尽管拉曼信号是从细胞中的随机选择的小焦点体积获得的，但通过显微镜对单细胞群体分数的测量，证实了随着年龄和盐胁迫的增加，叶绿素拉曼模式强度的下降。在盐胁迫下，叶绿素和类胡萝卜素模式的拉曼强度波动（I）都很高，这可能是由于叶绿素/类胡萝卜素含量和组成的变化，或 C 中色素的构象变化 Reinhardtii 细胞。有趣的是，在所有生长条件下，叶绿素 a 拉曼模式强度都与β-胡萝卜素高度相关，这表明在光捕获复合物色素中存在高度的协同作用，即使在盐胁迫下也是如此。因此，我们证明了使用微拉曼光谱进行非侵入性色素分析在开发高生物量产量和适当收获时间的盐胁迫条件优化方面的有用性，以获得具有所需化学成分的类胡萝卜素。
