Aspergillus niger

Aspergillus niger has been engineered and optimized for industrial production to a degree rivaling any microorganism. This common black mold produces citric acid at industrial scale—over 2 million tons annually—along with enzymes, organic acids, and secondary metabolites. Understanding fungal metabolism in model yeasts enabled the rational engineering that made A. niger an industrial platform. The same metabolic pathways studied for their role in yeast longevity produce commercially valuable compounds in Aspergillus.

The citric acid production pathway illustrates metabolic engineering in action. A. niger naturally produces citric acid under specific stress conditions—high sugar, low pH, limited trace metals. Industrial processes recreate and optimize these conditions, pushing the fungus toward maximum citric acid output. Understanding the metabolic regulation that governs this production—much of it conserved from yeast—enabled targeted genetic modifications that further increased yields. Basic research on yeast metabolism thus contributed to industrial biotechnology.

A. niger also demonstrates the aging-related concept of resource allocation trade-offs. Fungi can allocate metabolic resources toward growth, stress resistance, or secondary metabolite production. Industrial strains sacrifice growth rate and stress resistance for production capacity. This trade-off parallels the longevity-fertility trade-offs studied in aging research: resources invested in one biological function are unavailable for others. A. niger's industrial optimization represents artificial selection for specific resource allocation patterns.