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 comple-ment 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 resist-ance, yielded an enhanced carbon assimilation rate in photobioreactor.

Combined resistance to oxidative stress and reduced antenna size enhance light-to-biomass conversion efficiency in Chlorella vulgaris cultures

MANNINO, GIUSEPPE;M. Maffei;
2019

Abstract

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 comple-ment 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 resist-ance, yielded an enhanced carbon assimilation rate in photobioreactor.
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https://link.springer.com/epdf/10.1186/s13068-019-1566-9?author_access_token=2zgUCCz2HVmGir-CbMuPC2_BpE1tBhCbnbw3BuzI2RMaJ-FiqgTlS76blznuuLBwpyRNqK96l6HBXO-XEg9GKQOOUHj7a6MBSrl3Ev0FhViR3MFk0PfyYVPVe5BU_uKy6EwdZA0rpcqeFROTPv2MeQ==
Microalgae, Chloroplast, Biofuel, Excess light, Photoprotection, Singlet oxygen, Biomass
Dall’Osto L., Cazzaniga S., Guardini Z., Barera S., Benedetti M., G. Mannino, M. Maffei, Bassi R.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2318/1711882
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