Guardini Zeno, Dall'Osto Luca, Barera Simone, Jaberi Mehrdad, Cazzaniga Stefano, Vitulo Nicola, Bassi Roberto
Dipartimento Di Biotecnologie, Università Di Verona, Strada Le Grazie 15, 37134 Verona, Italy.
Plants (Basel). 2021 May 1;10(5):911. doi: 10.3390/plants10050911.
Microalgae represent a carbon-neutral source of bulk biomass, for extraction of high-value compounds and production of renewable fuels. Due to their high metabolic activity and reproduction rates, species of the genus are highly productive when cultivated in photobioreactors. However, wild-type strains show biological limitations making algal bioproducts expensive compared to those extracted from other feedstocks. Such constraints include inhomogeneous light distribution due to high optical density of the culture, and photoinhibition of the surface-exposed cells. Thus, the domestication of algal strains for industry makes it increasingly important to select traits aimed at enhancing light-use efficiency while withstanding excess light stress. Carotenoids have a crucial role in protecting against photooxidative damage and, thus, represent a promising target for algal domestication. We applied chemical mutagenesis to and selected for enhanced tolerance to the carotenoid biosynthesis inhibitor norflurazon. The (norflurazon-resistant) strains showed an increased carotenoid pool size and enhanced tolerance towards photooxidative stress. Growth under excess light revealed an improved carbon assimilation rate of strains with respect to WT. We conclude that domestication of by optimizing both carotenoid/chlorophyll ratio and resistance to photooxidative stress, boosted light-to-biomass conversion efficiency under high light conditions typical of photobioreactors. Comparison with strains previously reported for enhanced tolerance to singlet oxygen, reveals that ROS resistance in is promoted by at least two independent mechanisms, only one of which is carotenoid-dependent.
微藻是一种碳中性的大量生物质来源，可用于提取高价值化合物和生产可再生燃料。由于其高代谢活性和繁殖率，该属的物种在光生物反应器中培养时具有很高的生产力。然而，野生型菌株存在生物学局限性，与从其他原料中提取的产品相比，藻类生物产品价格昂贵。这些限制包括由于培养物的高光密度导致的光分布不均匀，以及表面暴露细胞的光抑制。因此，为工业目的对藻类菌株进行驯化时，选择旨在提高光利用效率同时耐受过量光胁迫的性状变得越来越重要。类胡萝卜素在防止光氧化损伤方面起着关键作用，因此是藻类驯化的一个有前景的目标。我们对该属应用化学诱变，并选择对类胡萝卜素生物合成抑制剂氟草敏具有增强耐受性的菌株。该属（耐氟草敏）菌株显示类胡萝卜素库大小增加，对光氧化胁迫的耐受性增强。在过量光照下生长表明，该属菌株相对于野生型具有更高的碳同化率。我们得出结论，通过优化类胡萝卜素/叶绿素比率和对光氧化胁迫的抗性来驯化该属，可提高在光生物反应器典型的高光条件下光到生物量的转化效率。与先前报道的对单线态氧耐受性增强的菌株进行比较，结果表明该属中的活性氧抗性由至少两种独立机制促进，其中只有一种是类胡萝卜素依赖性的。
