Optimizing biomass and energy feedstock production from algal-bacterial biofilms treating swine wastewater: The role of organic carbon sources

This study establishes a novel strategy for the valorization of swine wastewater by co-producing lipid-rich and protein-rich microbial biomass using organic carbon-amended algal-bacterial biofilms. Among four carbon sources in the immobilized biofilm system, sodium acetate (C/N = 18) proved optimal, achieving a biomass productivity of 45.43 g/m²/d, which was 5.71 times greater than suspended co-cultures. Crucially, this system significantly enhanced the content and yield of valuable bioproducts, with lipid and protein contents reaching 30.46% and 42.39%, corresponding to yields of 110.70 g/m² and 154.06 g/m², respectively. The robust system performance also ensured high removal efficiencies for nutrients (NH₄⁺-N: 99.44%; TN: 98.02%; TP: 91.55%) and the antibiotic sulfamethazine (SM2: 75.63%), underscoring its efficacy in simultaneous wastewater treatment. Mechanistic investigations attributed the superior performance to sodium acetate-driven metabolic upregulation. This was marked by the extracellular accumulation of L-glutamate — a central metabolite in nitrogen assimilation — and hydrophobic amino acids, which collectively indicate a enhanced metabolic flux toward the synthesis of cellular proteins and lipids. This work demonstrates a sustainable, carbon-enhanced biofilm platform for the simultaneous recovery of energy (biodiesel precursor) and feed (protein) resources from swine wastewater.