The transcription factor CgGCN4 coordinates carbon-nitrogen metabolism to improve glycerol and ethanol biosynthesis under low-nitrogen stress in yeast

Nitrogen limitation suppresses growth and target metabolite synthesis of industrial yeast, and the key transcription factor coordinating carbon-nitrogen balance in Candida glycerinogenes remains unclear. This work identified CgGCN4 as the core effector of nitrogen starvation response: screen nitrogen-starvation responsive transcription factor in C. glycerinogenes; characterize physiological function via overexpression and antisense repression in glycerol-producing yeast; test cross-species function by heterologous expression in S. cerevisiae for ethanol fermentation application. qRT-PCR reveals nitrogen starvation activates three nutrient-sensing pathways, with CgGCN4 showing the highest transcript level (4.2). At 84 h fermentation, CgGCN4-OE consumes 250.2 g/L glucose, yields 122.6 g/L glycerol and reaches OD600 of 45.6, outperforming wild type. Transcriptomics demonstrates CgGCN4 co-upregulates glycolysis, TCA and amino acid synthesis to balance C/N metabolism. Its conserved function is validated in Saccharomyces cerevisiae. In 5 L fed-batch culture, engineered Sc-BNA-MG produces 67.7 g/L ethanol (10.1% higher than control), with intracellular NAD(H) pool rising by 27.5% at 6 h. CgGCN4 serves as a cross-species regulatory hub mitigating low-nitrogen stress, a promising target for yeast factory engineering.