Fast and easy edible protein production by nitrogen-supplemented koji fermentation.

The continuous increase in the global population has led to a rise in the demand for protein. However, conventional meat production has adverse environmental effects. Thus, developing alternative ways to produce edible protein with high efficiency and low cost is necessary. In this study, a novel protein production process was developed based on traditional koji fermentation, i.e., solid-state Aspergillus oryzae cultivation on grains. By supplementing nitrogen sources into rice and maize grains, the protein content of fermented products reached to 12.3% and 13.2% and the amount of total protein was increased to 2.32-fold and 1.58-fold, respectively. In addition, koji fermentation enhanced the content of lysine, which is the limiting amino acid for humans and livestock. Nitrogen-supplemented koji fermentation is a practical technology for the quick protein enrichment of cereal grains without the need for advanced facilities, indicating its great application potential in alleviating the anticipated global shortage of protein-rich foods.