Analytically monitored cultivation of Arthrospira platensis on food waste extracts to compose a sustainable, low-prized, Zarrouk-based medium

Abstract

A sustainable, low-cost medium based on food waste for cultivating the cyanobacterium Arthrospira platensis (A. platensis) was investigated. Zarrouk medium components, especially phosphate, were substituted with extracts from beetroot peel, brewer’s grains, and walnut press cake. Ion concentrations of magnesium, calcium, iron, potassium, sodium, phos-phate, nitrate, sulfate, and chloride were analyzed to determine the optimal medium composition. Walnut press cake and brewer’s grains extracts showed high potential due to their magnesium, calcium, and phosphate content. Brewer’s grains extracts also provided glucose as an additional carbon source. Cultivations in shaking flasks and a photobioreactor (PBR) monitored cell growth through optical density and biomass concentration. The excess of magnesium and reduced phos-phate concentrations positively affected biomass production. A. platensis’s ability to metabolize glucose resulted in 68% higher biomass production. Growth in brewer’s grains extract required no additional phosphate. PBR cultivation showed A. platensis consumed significant magnesium and nitrate, achieving higher biomass concentrations with optimized gas exchange and light reflection systems.

Keywords

• Food waste
• Zarrouk
• Arthrospira platensis
• Spirulina
• cyanobacteria
• valorization