Combined resistance to oxidative stress and reduced antenna size enhance light-to-biomass conversion efficiency in Chlorella vulgaris cultures
Combined resistance to oxidative stress and reduced antenna size enhance light-to-biomass conversion efficiency in Chlorella vulgaris cultures
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DOI：
10.1186/s13068-019-1566-9
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发表时间：
2019-09-16
影响因子：
6.3
通讯作者：
Bassi, Roberto
中科院分区：
文献类型：
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作者：
Dall'Osto, Luca;Cazzaniga, Stefano;Bassi, Roberto
微藻是富含脂质的生物质的有效生产者，使其成为开发可持续能源的关键组成部分，并成为化石燃料的替代品。小球藻由于其在光生物反应器中的快速生长速率而受到特别关注。然而，生物方面的制约因素仍然使生物燃料的高成本与廉价石油之间存在巨大差距，从而阻碍了生产二氧化碳中性生物燃料的前景。一个关键问题是光在培养物中的不均匀分布导致光的低效使用，这会产生表面暴露细胞的光抑制和内层的暗化。因此，有效的生物燃料生产需要驯化，包括降低培养物光密度和增强光保护的性状。结果对普通小球藻进行了两步诱变和表型选择。首先，选择淡绿色突变体（PG-14），相对于WT，每个细胞的叶绿素含量和每个PSII的LHCII补体都降低了50%。与WT相比，PG-14显示出增加30%的光子转化为生物质的效率。PG-14的第二步诱变，然后选择对虎红的更高耐受性，导致分离出对单线态氧表现出更高抗性的浅绿色基因型（菌株SOR）。在强光条件下的光生物反应器中的生长显示相对于PG-14，SOR菌株的生物量生产增强。与野生型菌株相比，淡绿色+ sor基因型的生物量产量提高了68%。结论驯化小球藻等微藻，通过优化光分布和ROS抗性，提高了光生物反应器中的碳同化速率。
Background Microalgae are efficient producers of lipid-rich biomass, making them a key component in developing a sustainable energy source, and an alternative to fossil fuels. Chlorella species are of special interest because of their fast growth rate in photobioreactors. However, biological constraints still cast a significant gap between the high cost of biofuel and cheap oil, thus hampering perspective of producing CO2-neutral biofuels. A key issue is the inefficient use of light caused by its uneven distribution in the culture that generates photoinhibition of the surface-exposed cells and darkening of the inner layers. Efficient biofuel production, thus, requires domestication, including traits which reduce optical density of cultures and enhance photoprotection. Results We applied two steps of mutagenesis and phenotypic selection to the microalga Chlorella vulgaris. First, a pale-green mutant (PG-14) was selected, with a 50% reduction of both chlorophyll content per cell and LHCII complement per PSII, with respect to WT. PG-14 showed a 30% increased photon conversion into biomass efficiency vs. WT. A second step of mutagenesis of PG-14, followed by selection for higher tolerance to Rose Bengal, led to the isolation of pale-green genotypes, exhibiting higher resistance to singlet oxygen (strains SOR). Growth in photobioreactors under high light conditions showed an enhanced biomass production of SOR strains with respect to PG-14. When compared to WT strain, biomass yield of the pale green + sor genotype was enhanced by 68%. Conclusions Domestication of microalgae like Chlorella vulgaris, by optimizing both light distribution and ROS resistance, yielded an enhanced carbon assimilation rate in photobioreactor.