posted on 2019-09-10, 17:44authored byDiyuan Wang, Yi-Chun Lai, Amanda L. Karam, Francis L. de los Reyes, Joel J. Ducoste
We developed a new dynamic model
to characterize how light and
nitrogen regulate the cellular processes of photosynthetic microalgae
leading to transient changes in the production of neutral lipids,
carbohydrates, and biomass. Our model recapitulated the versatile
neutral lipid synthesis pathways via (i) carbon reuse from carbohydrate
metabolism under nitrogen sufficiency and (ii) fixed carbon redirection
under nitrogen depletion. We also characterized the effects of light
adaptation, light inhibition hysteresis, and nitrogen limitation on
photosynthetic carbon fixation. The formulated model was calibrated
and validated with experimental data of Dunaliella viridis cultivated in a lab-scale photobioreactor (PBR) under various light
(low/moderate/high) and nitrogen (sufficient/limited) conditions.
We conducted the identifiability, uncertainty, and sensitivity analyses
to verify the model reliability using the profile likelihood method,
the Markov chain Monte Carlo (MCMC) technique, and the extended Fourier
Amplitude Sensitivity Test (eFAST). Our model predictions agreed well
with experimental observations and suggested potential model improvement
by incorporating a lipid degradation mechanism. The insights from
our model-driven analysis helped improve the mechanistic understanding
of transient algae growth and bioproducts formation under environmental
variations and could be applied to optimize biofuel and biomass production.