Biosynthesis and nutritional evaluation of iron-enriched Aspergillus oryzae as a novel iron supplement

Fungi possess an inherent ability to accumulate trace elements such as iron. In this study, we employed the Generally Recognized As Safe (GRAS) fungus Aspergillus oryzae (A. oryzae) A02 to biosynthesize an iron-enriched biomass (Fe-AA) and utilized a murine model to assess its physiological effects. Systematic optimization of fermentation parameters facilitaed pilot-scale production yielding mycelium with an organic iron content of 6.88 % (w/w), which represents the highest reported level for an A. oryzae-based iron supplement to date. Advanced characterization techniques (FTIR, SEM, TEM-EDS) and transcriptomic analysis revealed that key genes involved in iron uptake, storage, and transport exhibited distinct expression profiles, in response to varying iron concentrations. This finding indicates a highly efficient and tightly regulated iron homeostasis network within A. oryzae A02. Additionally, it was observed that Fe-AA was effectively absorbed in normal mice via the intestinal epithelial divalent metal transporter 1 (DMT1) pathway, resulting in high bioavailability of ferrous iron, which was subsequently stored in the liver. Moreover, supplementation with Fe-AA promoted villus elongation in the duodenum and jejunum, modulated gut microbiota composition, and stimulated the production of beneficial short-chain fatty acids, demonstrating its intestinal health benefits. Our findings elucidate the biosynthetic mechanisms underlying high iron enrichment in A. oryzae and establish Fe-AA as a promising iron supplement, thus supporting its further development.