Branched-chain amino acid-driven metabolic coordination synchronizes lipid and astaxanthin production with biomass valorization in Haematococcus pluvialis

The integrated valorization of microalgal biomass remains challenging due to the trade-offs between target metabolite production and residual biomass utilization. This study demonstrates a branched-chain amino acid (BCAA)-driven circular bioprocessing strategy that coordinately enhances Haematococcus pluvialis biomass productivity and cascade resource recovery. BCAA supplementation was associated with significant increases in levels of respiratory metabolites, accelerating pyrimidine and purine nucleotide biosynthesis in a manner conducive to cell proliferation. These higher respiratory metabolite levels also enabled higher levels of substrate biosynthesis, producing lipids, proteins, and carbohydrates that ultimately caused greater biomass accumulation. Crucially, although astaxanthin content per cell remained stable, total yield scaled with biomass growth. Specifically, Supplementation with 100 μM leucine triggered a 37.5 % increase in astaxanthin yield and 29.1 % biomass accumulation, while elevating lipid (19.7 %), protein (31.0 %), and carbohydrate (43.8 %) contents. This work provides the important evidence that respiratory metabolite redirection via BCAA supplementation can synchronize high-value carotenoid production with multiproduct biorecovery, establishing a paradigm for microalgal circular bioeconomy. • A promising strategy for enhancing microalgal multiproduct production was developed. • Exogenous BCAAs enhanced respiratory metabolite levels and biomass accumulation. • Higher metabolite levels increased lipids, proteins and carbohydrate production. • Exogenous BCAAs improved H. pluvialis astaxanthin yield by enhancing cell growth.