Xie Yuxiao, Xiong Xiaochao, Chen Shulin
Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA.
Microorganisms. 2021 May 15;9(5):1068. doi: 10.3390/microorganisms9051068.
Research on enhancing lutein content in microalgae has made significant progress in recent years. However, strategies are needed to address the possible limitations of microalgae as practical lutein producers. The capacity of lutein sequestration may determine the upper limit of cellular lutein content. The preliminary estimation presented in this work suggests that the lutein sequestration capacity of the light-harvesting complex (LHC) of microalgae is most likely below 2% on the basis of dry cell weight (DCW). Due to its nature as a structural pigment, higher lutein content might interfere with the LHC in fulfilling photosynthetic functions. Storing lutein in a lipophilic environment is a mechanism for achieving high lutein content but several critical barriers must be overcome such as lutein degradation and access to lipid droplet to be stored through esterification. Understanding the mechanisms underlying lipid droplet biogenesis in chloroplasts, as well as carotenoid trafficking through chloroplast membranes and carotenoid esterification, may provide insight for new approaches to achieve high lutein contents in algae. In the meantime, building the machinery for esterification and sequestration of lutein and other hydroxyl-carotenoids in model microorganisms, such as yeast, with synthetic biology technology provides a promising option.
近年来，提高微藻中叶黄素含量的研究取得了重大进展。然而，需要采取策略来解决微藻作为实际叶黄素生产者可能存在的局限性。叶黄素的螯合能力可能决定细胞中叶黄素含量的上限。这项工作中的初步估计表明，基于干细胞重量（DCW），微藻捕光复合体（LHC）的叶黄素螯合能力很可能低于2%。由于叶黄素作为一种结构色素的性质，较高的叶黄素含量可能会干扰LHC履行光合作用功能。将叶黄素储存在亲脂环境中是实现高叶黄素含量的一种机制，但必须克服几个关键障碍，如叶黄素降解以及通过酯化作用进入脂质滴进行储存。了解叶绿体中脂质滴生物合成的潜在机制，以及类胡萝卜素通过叶绿体膜的运输和类胡萝卜素酯化作用，可能为实现藻类中叶黄素高含量的新方法提供思路。与此同时，利用合成生物学技术在模型微生物（如酵母）中构建叶黄素和其他羟基类胡萝卜素的酯化和螯合机制提供了一个有前景的选择。
