Improvement of feed nutritional value of sprayed corn bran through two-stage solid-state fermentation by non-protein nitrogen utilization microorganisms.

Background: Sprayed corn bran - a by-product of starch extraction from corn by wet-milling technology - is often used as feedstuff to partially substitute protein feed. However, the utilization of sprayed corn bran is greatly restricted in feed because of its low protein content and poor taste.

Results: Three microbes with non-protein nitrogen utilization ability were screened and applied to the solid-state fermentation of sprayed corn bran and urea with incubation of the fungus Aspergillus niger, and a two-stage (aerobic and anaerobic) solid-state fermentation was established. The optimum aerobic fermentation conditions were determined by response surface methodology. When the fermentation time, temperature, moisture, and inoculated amount were 72 h, 36 °C, 65% (v/w), and 20% (v/w), respectively, the crude protein content of the sprayed corn bran could reach 348 g kg. Finally, the nutrient components were characterized during the two-stage solid-state fermentation process. The conversion rate of the urea was 54.8%. The crude protein content was increased from 284 to 351 g kg, which comprises 293 g kg of protein, amino acids and peptides. In particular, contents of the functional amino acids proline and arginine were increased by 64% and 130%, respectively. The mycotoxins zearalenone and aflatoxin were lower than the National Feed Safety Standards. Meanwhile, the two-stage solid-state fermentation enriched beneficial living microorganisms and improved feed flavor.

Conclusion: This study could efficiently improve the nutritional value of sprayed corn bran, enabling the reuse of agricultural by-products, with the potential to help alleviate the shortage of protein feed. © 2025 Society of Chemical Industry.