Hydrodynamic cues enhance algal lipid production while sustaining biomass in motile species

Achieving enhanced lipid yield without compromising biomass is one of the long-standing challenges in our quest to produce algal biofuel sustainably. Multiple factors, including temperature, nutrients and light conditions impact lipid production, however such lipid-enhancing strategies often lead to reduced biomass, thereby offsetting the total volume of lipid recovered. Hydrodynamic cues remain poorly studied, specifically in the context of lipid production in motile algae, concurrently with biomass generation and photo-physiology, a key fitness parameter. By imposing hydrodynamic cues to biophysically stress distinct strains of raphidophyte Heterosigma akashiwo at specific time points along the growth stages (indicating different nutritional states), we quantify the lipid production, alongside algal biomass and photo-physiology. Early induction (hydrodynamic cues implemented during the lag phase) and delayed induction (hydrodynamic cues implemented during the exponential phase) were studied. Delayed induction of hydrodynamic cues suppressed growth and photo-physiology without significant enhancement of lipid production, however, early induction allowed to significantly increase lipid content, up to 300%, without observable changes in biomass and photo-physiology. Based on this, we propose a hydrodynamic strategy for enhanced lipid production with sustained biomass and physiological fitness. This work presents hydrodynamic perturbation and its onset timing as tunable parameters to advance lipid production technologies across diverse motile species.