The Role of Light Wavelengths in Regulating Algal-Bacterial Granules Formation, Protein and Lipid Accumulation, and Microbial Functions

This study explored the role of light wavelengths in regulating granules formation, protein and lipid production, and microbial functions. Bacterial granular sludge (BGS, R0) was most conducive to forming algal-bacterial granules sludge under blue (R2) light with highest chlorophyll a (10.2 mg/g-VSS) and diameter (1.8 mm), followed by red (R1) and white (R3) lights. R0-R3 acquired high protein contents (> 164.8 mg/g-VSS) with essential amino acid above 44.4%, all of which were suitable for recycling, but R2 was the best. Also, blue light significantly increased total lipid production, while red light promoted the accumulation of some unsaturated fatty acids (C18:2 and C18:3). Some unique algae and dominant bacteria (e.g., Stigeoclonium, Chlamydomonas, and Flavobacteria) enrichment and some key functions (e.g., amino acid, fatty acid, and lipid biosynthesis) up-regulation in R2 might help to improve proteins and lipids quality. Combined, this study provides valuable guidance for protein and lipid recovery from ABGS