Extreme Microalga Turns Shrimp and Sludge Waste Into Protein-Rich Biomass

A new study published in Waste and Biomass Valorization describes a process that uses an extreme microalga to turn shrimp processing waste and aquaculture sludge into protein-rich biomass. Researchers led by Corina Kleps and Daniel Pleissner grew the thermo-acidophilic red microalga Galdieria sulphuraria on hydrolysates derived from residues from a German shrimp facility. The resulting biomass reached up to 62% protein and contained measurable amounts of phycocyanin, a commercially valuable blue pigment. The alga is cultured at very acidic conditions (pH 1.8) and 45°C in darkness, relying on organic substrates rather than photosynthesis. This allows non-sterile operation because harsh conditions suppress many contaminants. The team tested multiple hydrolysis routes, including enzymes and 1% sulfuric acid pretreatment at 90°C, before digestion. The work targets the nutritional recovery of waste that otherwise drives eutrophication and greenhouse-gas emissions.