Valorization of Food Waste-Derived Brown Juice as a Biostimulant Supplement for Spirulina Cultivation: A Trade-Off Between Protein Enrichment and Biomass Productivity

Author : Wildan Suhartini, S. Reyhan Yavuz, Nevien Elhawat, Tarek Alshaal, Eva Domokos-Szabolcsy, Nora Bakonyi

Abstract : Global food waste necessitates innovative valorization strategies. This study evaluated by-products from leaf protein concentrate, i.e., brown juice (BJ) from green pea (G), triticale (T), and their mixture (GT), fermented with lactic acid (LA) or lactic acid bacteria (LB), as a Spirulina supplement. BJ was added at 1–5% (v/v) to monitor growth, biomass, and crude protein over 11 days. BJ significantly increased protein content, peaking at 75.44% in GT-LA 1% versus 62.24% in control (+21.21%). However, biomass yield declined sharply (up to 61%), offsetting compositional gains. Consequently, total protein yield per liter decreased across all treatments (net losses: −0.12 to −0.65 g/L). The best balance was observed in T-LA at 2.5%, achieving the highest Culture Efficiency Index (0.37) and competitive growth kinetics (μ=0.21 day⁻¹). These findings reveal a physiological trade-off that BJ induces stress-driven protein accumulation, likely mediated by phenolic compounds, while suppressing cell proliferation. Although suboptimal for mass protein production, BJ offers a viable route for upcycling food-processing residues into functionally enriched Spirulina for specialized feed applications, provided that low LA-fermented concentrations are used. This study underscores the critical importance of dose optimization and matrix selection in food waste biorefinery strategies.

Keywords : Brown Juice Valorization, Food Waste Minimization, Circular Bioeconomy, Sustainable Food Production

Conference Name : International Conference on Food Waste Minimization (ICFWM - 26)

Conference Place : Sarajevo, Bosnia and Herzegovina

Conference Date : 17th Sep 2026