Domestication of the green alga Chlorella sorokiniana: reduction of antenna size improves light-use efficiency in a photobioreactor

Biotechnology for Biofuels

Stefano Cazzaniga¹  Luca Dall’Osto¹  Joanna Szaub²  Luca Scibilia¹  Matteo Ballottari¹  Saul Purton²  Roberto Bassi¹ 

[1] Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie, Verona 15-37134, Italy

[2] Institute of Structural and Molecular Biology, University College London, London WC1E 6BT, UK

关键词: Light-use efficiency;    Antenna size;    Biofuel;    Biomass;    Photobioreactor;    Photosynthesis;    Chlorella sorokiniana;   

Others  :  1084313
DOI  :  10.1186/s13068-014-0157-z

 received in 2014-06-25, accepted in 2014-10-07,  发布年份 2014

【 摘 要 】

Background

The utilization of biomass from microalgae for biofuel production is one of the key elements for the development of a sustainable and secure energy supply. Among the different microalgae, Chlorella species are of interest because of their high productivity, high lipid content, and resistance to the high light conditions typical of photobioreactors. However, the economic feasibility of growing algae at an industrial scale is yet to be realized, in part because of biological constraints that limit biomass yield. A key issue is the inefficient use of light due to uneven light distribution, and the dissipation of excess absorbed light as heat. The successful implementation of biofuel production facilities requires the development of algal strains with enhanced light use efficiency in photobioreactors. Such domestication strategies include decreasing the absorption cross section in order to enhance light penetration, increasing the size of metabolic sinks per chlorophyll and minimizing feedback energy dissipation.

Results

In this work we applied random mutagenesis and phenotypic selection to the thermotolerant, fast-growing Chlorella species, C. sorokiniana. Truncated antenna mutants (TAMs) were selected that exhibited a lower fluorescence yield than the wild-type (WT) strain. Six putatively interesting mutants were selected by high throughput fluorescence video imaging, two of which, TAM-2 and TAM-4, were found to have approximately half the chlorophyll content per cell and LHCII complement per PSII with respect to the WT. In batch culture, TAM-2 showed an increased photon use efficiency, yielding a higher P_max at saturating irradiances with respect to the WT. Cultivation of TAM-2 in both laboratory-scale and outdoor photobioreactors showed higher productivity than WT, with a 30% higher biomass yield in dense cell suspensions typical of industrial photobioreactors.

Conclusions

These results suggest that generation of mutants with low chlorophyll content can significantly improve the light-to-biomass conversion efficiency of C. sorokiniana under mass culture conditions. However, owing to the lack of sexual reproduction in this species, the presence of additional mutations might affect growth rate, suggesting that selection should include evaluation of multiple independent mutants for each desired phenotype.

【 授权许可】

   
2014 Cazzaniga et al.; licensee BioMed Central Ltd.

【 图 表 】

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