Light attenuation as a substitute for nutrient supply for maximizing protein content in Gracilaria cornea (Rhodophyta): Modeling nitrogen and phosphorus supplementation using a pharmacokinetic approach

Purpose: This study explores the potential of utilizing light stress as an alternative to nutrient pulse feeding to maximize protein content in a marine red seaweed. Methods: A land-based setup of seaweed culture tanks was established over two seasons in the easternmost Mediterranean Sea in Israel. Culture tanks were randomly assigned to different regimes of light intensity and nutrient pulse feeding. In-situ spectral measurements and Artificial Neural Network (ANN) algorithm were used to determine protein content accumulation. A pharmacokinetic approach determined nutrient dose efficacy and a decision support model identified biotic and abiotic factors affecting protein yield and optimal harvesting day. Results: The cultivation day, treated as a nominal classification fixed variable, was significant in capturing the non-linear response of protein expression. Pulse feeding dosage at the start point and light intensity attenuation were also significant. Results demonstrated a regulated relationship between light attenuation and nutrient assimilation, modulating an adaptive biochemical response of protein manifestation utilized for photosynthesis. Optimal protein content of 19.08 % of seaweed dry weight was achieved at day 14, regardless of fertilization regimes. This was stimulated by high-level pulse additions of 2.0 mM NH4+ and 0.2 mM PO₄³⁻ at the start, followed by nitrogen starvation and light intensity attenuation to around 8 μmol photons m⁻² s⁻¹. Conclusion: The suggested cultivation strategy enhances photosynthetic activity and protein biosynthesis, reducing the need for inorganic fertilization and associated costs. This approach promotes environmental and financial sustainability in protein enriched seaweed production.