Intracellular Spectral Recompositioning of Light: A Novel Strategy for Improving Photosynthetic Efficiency of Diatoms

Intracellular Spectral Recompositioning of
Light: A Novel Strategy for Improving Photosynthetic Efficiency of Diatoms

Weiqi
Fu^1,2,3, Amphun Chaiboonchoe^1,2, Mehar Sultana²,
Kourosh Salehi-Ashtiani^1,2

¹Laboratory of Algal, Systems, and
Synthetic Biology, Division of Science and Math, and ²Center for
Genomics and Systems Biology (CGSB), New York University Abu Dhabi, P.O. Box
129188, Abu Dhabi, UAE

³Center for Systems Biology and Faculty of
Industrial Engineering, Mechanical Engineering and Computer Science, School of
Engineering and Natural Sciences, University of Iceland, Reykjavik 101, Iceland

Abstract

In order to
concurrently address global resource scarcity and the impending climate change,
the use of photosynthetic diatoms can provide an exciting solution for sustainable
production of biofuels and bioactive compounds. However, photosynthetic
efficiency in diatoms needs to be optimized to reduce the energy costs for
sustainable biomass production. We have developed and implemented a strategy herein
referred to as Intracellular Spectral Recompositioning of
light (or ISR), which can increase the quantum yield of light if the
otherwise wasted portion of blue light is shifted to green, which diatoms have
evolved to harvest through accessory pigments. We demonstrate that ISR
can be employed chemically or biogenically to improve photosynthesis in the
diatom Phaeodactylum tricornutum in photobioreactors. Genetically engineered
diatom cells with enhanced green fluorescent protein (EGFP) achieved desired spectrum
recompositioning with high photo-stability in batch culture. These engineered
strains exhibited higher efficiency of photosynthesis than their wild type
counterpart by 30%. This increase can be attributed to an increase of quantum
yields in photosystem II in diatom cells under light stress conditions. Long-term
experiments demonstrated the stability of EGFP transformants and the robustness
of GFP expression upon the presence of nitrate during cultivation. Pond
simulator experiments also observed the GFP transformants could outperform
their wild type counterpart. In addition, genome-scale transcriptome and gene
set enrichment analysis of the obtained strains will be presented in comparison
to the wild type to characterize these strains at the system level. The ISR
approach is expected to be broadly applicable toward improving energy
efficiency for cultivation of microalgae at industrial production scales.