Increased consumer awareness for healthier and more sustainable products has driven the search for naturally sourced compounds as substitutes for chemically synthesized counterparts. Research on pigments of natural origin, such as carotenoids, particularly lutein, has been increasing for over three decades. Lutein is recognized for its antioxidant and photoprotective activity. Its ability to cross the blood-brain barrier allows it to act at the eye and brain level and has been linked to benefits for vision, cognitive function and other conditions. While marigold flower is positioned as the only crop from which lutein is extracted from and commercialized, microalgae are proposed as an alternative with several advantages over this terrestrial crop. The main barrier to scaling up lutein production from microalgae to the commercial level is the low productivity compared to the high costs. This review explores strategies to enhance lutein production in microalgae by emphasizing the overall productivity over lutein content alone. Evaluation of how culture parameters, such as light quality, nitrogen sufficiency, temperature and even stress factors, affect lutein content and biomass development in batch phototrophic cultures was performed. Overall, the total lutein production remains low under this metabolic regime due to the low biomass productivity of photosynthetic batch cultures. For this reason, we describe findings on microalgal cultures grown under different metabolic regimes and culture protocols (fed-batch, pulse-feed, semi-batch, semi-continuous, continuous). After a careful literature examination, two-step heterotrophic or mixotrophic cultivation strategies are suggested to surpass the lutein productivity achieved in single-step photosynthetic cultures. Furthermore, this review highlights the urgent need to develop technical feasibility studies at a pilot scale for these cultivation strategies, which will strengthen the necessary techno-economic analyses to drive their commercial production.

中文翻译：

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微藻生产叶黄素的观点不断演变 - 关注生产力和异养培养


消费者对更健康、更可持续产品的认识不断提高，推动了对天然来源化合物作为化学合成化合物替代品的寻找。三十多年来，对天然色素（例如类胡萝卜素，特别是叶黄素）的研究不断增加。叶黄素因其抗氧化和光保护活性而闻名。它穿越血脑屏障的能力使其能够在眼睛和大脑水平发挥作用，并与视力、认知功能和其他条件的益处有关。虽然万寿菊花被定位为唯一提取叶黄素并将其商业化的作物，但微藻被提议作为替代品，与这种陆生作物相比具有多种优势。将微藻叶黄素生产规模扩大到商业水平的主要障碍是与高成本相比生产率低。本综述探讨了通过强调整体生产力高于叶黄素含量来提高微藻叶黄素产量的策略。对分批光养培养中光质量、氮充足度、温度甚至应激因素等培养参数如何影响叶黄素含量和生物量发育进行了评估。总体而言，由于光合分批培养物的生物量生产率较低，在此代谢模式下叶黄素总产量仍然较低。因此，我们描述了在不同代谢模式和培养方案（补料分批、脉冲补料、半分批、半连续、连续）下生长的微藻培养物的发现。经过仔细的文献检查后，建议采用两步异养或混合营养培养策略，以超越单步光合培养中实现的叶黄素生产力。 此外，本次审查强调迫切需要对这些种植策略进行试点规模的技术可行性研究，这将加强必要的技术经济分析，以推动其商业化生产。