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Online monitoring of chlorophyll a fluorescence in Nannochloropsis oceanica to assess photochemical changes and the onset of lipid accumulation during nitrogen deprivation
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  • Mariana Carneiro,
  • Graziella Chini Zittelli,
  • Bernardo Cicchi,
  • Elefterios Touloupakis,
  • Cecilia Faraloni,
  • Inês Maia,
  • Hugo Pereira,
  • Tamára Santos,
  • Francisco Xavier Malcata,
  • Ana Otero,
  • João Varela,
  • Giuseppe Torzillo
Mariana Carneiro
LEPABE
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Graziella Chini Zittelli
National Research Council
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Bernardo Cicchi
National Research Council Department of Biological Agricultural and Food Sciences
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Elefterios Touloupakis
National Research Council Department of Earth System Science and Environment Technologies
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Cecilia Faraloni
National Research Council Department of Biological Agricultural and Food Sciences
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Inês Maia
CCMAR
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Hugo Pereira
GreenCoLab
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Tamára Santos
CCMAR
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Francisco Xavier Malcata
LEPABE
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Ana Otero
Universidade de Santiago de Compostela
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João Varela
CCMAR
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Giuseppe Torzillo
Centro de Investigación en Ciencias del Mar y Limnologia
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Abstract

In this work, we applied online chlorophyll a fluorescence measurements to monitor the changes in the photochemical parameters both in nitrate-deplete and nitrate-replete cultures of Nannochloropsis oceanica, in addition to biochemical parameters such as growth, lipid, fatty acid, and pigment contents. Under nitrate-replete conditions, growth was promoted along with pigment content, while total lipid content and fatty acid saturation level diminished. Under nitrate-deplete conditions, cultures showed an increased de-epoxidation state of the xanthophyll cycle pigments. Fast transients revealed a poor processing efficiency for electron transfer beyond QA, which was in line with the low electron transport rate due to nitrate depletion. Lipid content and the de-epoxidation state were the first biochemical parameters triggered by the change in nutrient status, which coincided with a 20% drop in the online effective quantum yield of PSII (ΔF/Fm’), and a raise in the Vj measurements. A good correlation was found between the changes in ΔF/Fm’ and lipid content (r=-0.96, p<0.01). The results confirm the reliability and applicability of online fluorescence measurements to monitor lipid induction in N. oceanica.

Peer review status:UNDER REVIEW

18 May 2021Submitted to Biotechnology and Bioengineering
19 May 2021Assigned to Editor
19 May 2021Submission Checks Completed
21 May 2021Reviewer(s) Assigned