The role of starch as transient energy buffer in synchronized microalgal growth in Acutodesmus obliquus

Mitsue Leon Saiki*, Ilse M. Remmers, Dirk E. Martens, Packo P. Lamers, René H. Wijffels, Douwe van der Veen

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

17 Citations (Scopus)

Abstract

Photosynthetic organisms have evolved to use light efficiently by scheduling their cellular processes, such as growth and cell division, at specific times of the day. During the day, fixed carbon is used for growth and is partially stored as carbohydrates (e.g., starch). It is commonly assumed that this accumulated starch is essential for fuelling up cell division at night. To test this hypothesis, this study investigates growth, cell division and presence of a transitory energy storage (TES) in both the wild-type and starchless mutant strain of Acutodesmus obliquus under light/dark (LD) cycles and nitrogen replete conditions. A. obliquus (formerly known as Scenedesmus obliquus) wild-type utilized light 20% more efficiently under LD regimes compared with continuous light. When exposed to LD regimes, the wild-type scheduled cell division in a 4-hour period starting 2 h before ‘sunset’. Starch acted as the major transitory energy storage (TES) compound: it was accumulated during the last part of the light period and was consumed throughout the entire dark period. The slm1 mutant, with a blocked starch synthesis pathway, showed diurnal rhythms in growth and cell division. However, no other carbohydrates nor triacylglycerols took over the role of TES compound in slm1. Therefore, in contrast to what is generally acknowledged, this study shows that neither starch nor any other major alternative TES is required for synchronized growth and cell division in A. obliquus. The starchless mutant did show a reduced growth and cell division rate compared to the wild-type. Starch, thus, plays a major role in efficient harnessing of light energy over LD cycles, likely because the ability to accumulate starch enhances biomass production capacity and accelerates cell division rate in A. obliquus.

Original languageEnglish
Pages (from-to)160-167
JournalAlgal Research
Volume25
DOIs
Publication statusPublished - 2017

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Keywords

  • Day/night cycles
  • Diurnal biochemical changes
  • Microalgae
  • Photosynthetic efficiency
  • Scenedesmus obliquus
  • Starchless mutant

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