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Domestication of the green alga Chlorella sorokiniana: reduction of antenna size improves light-use efficiency in a photobioreactor
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 resist...
Autores principales: | , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
BioMed Central
2014
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4210543/ https://www.ncbi.nlm.nih.gov/pubmed/25352913 http://dx.doi.org/10.1186/s13068-014-0157-z |
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author | Cazzaniga, Stefano Dall’Osto, Luca Szaub, Joanna Scibilia, Luca Ballottari, Matteo Purton, Saul Bassi, Roberto |
author_facet | Cazzaniga, Stefano Dall’Osto, Luca Szaub, Joanna Scibilia, Luca Ballottari, Matteo Purton, Saul Bassi, Roberto |
author_sort | Cazzaniga, Stefano |
collection | PubMed |
description | 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. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13068-014-0157-z) contains supplementary material, which is available to authorized users. |
format | Online Article Text |
id | pubmed-4210543 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2014 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-42105432014-10-29 Domestication of the green alga Chlorella sorokiniana: reduction of antenna size improves light-use efficiency in a photobioreactor Cazzaniga, Stefano Dall’Osto, Luca Szaub, Joanna Scibilia, Luca Ballottari, Matteo Purton, Saul Bassi, Roberto Biotechnol Biofuels Research Article 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. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13068-014-0157-z) contains supplementary material, which is available to authorized users. BioMed Central 2014-10-21 /pmc/articles/PMC4210543/ /pubmed/25352913 http://dx.doi.org/10.1186/s13068-014-0157-z Text en © Cazzaniga et al.; licensee BioMed Central Ltd. 2014 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. |
spellingShingle | Research Article Cazzaniga, Stefano Dall’Osto, Luca Szaub, Joanna Scibilia, Luca Ballottari, Matteo Purton, Saul Bassi, Roberto Domestication of the green alga Chlorella sorokiniana: reduction of antenna size improves light-use efficiency in a photobioreactor |
title | Domestication of the green alga Chlorella sorokiniana: reduction of antenna size improves light-use efficiency in a photobioreactor |
title_full | Domestication of the green alga Chlorella sorokiniana: reduction of antenna size improves light-use efficiency in a photobioreactor |
title_fullStr | Domestication of the green alga Chlorella sorokiniana: reduction of antenna size improves light-use efficiency in a photobioreactor |
title_full_unstemmed | Domestication of the green alga Chlorella sorokiniana: reduction of antenna size improves light-use efficiency in a photobioreactor |
title_short | Domestication of the green alga Chlorella sorokiniana: reduction of antenna size improves light-use efficiency in a photobioreactor |
title_sort | domestication of the green alga chlorella sorokiniana: reduction of antenna size improves light-use efficiency in a photobioreactor |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4210543/ https://www.ncbi.nlm.nih.gov/pubmed/25352913 http://dx.doi.org/10.1186/s13068-014-0157-z |
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