Solid-state fermentation of corn wet distiller grains and wheat bran with Trichoderma reesei and Candida utilis for improving feed value.

Background: Solid-state fermentation is one of the most effective methods for the high-value utilization of agro-industrial by-products. Co-fermentation of wet distiller grains and agricultural waste is an effective way to mitigate the feed shortage caused by corn consumption for bioethanol. It is still challenging to convert wet distiller grains and wheat bran to easily accessible carbon sources and adjust the balanced proportion of amino acids together by fermentation.

Results: Fermentation time, strain ratio, and the addition of ammonium sulfate have been verified to be the important factors influencing the symbiosis of Trichoderma reesei (T. reesei) and Candida utilis (C. utilis) in a mixed system of wet distiller grains and wheat bran. The optimum conditions were fermentation for 8 days, 2:1 (T. reesei: C. utilis) strain ratio, and addition of 4% ammonium sulfate. After fermentation, the cellulose degradation proportion reached 39.1%, and the hemicellulose degradation proportion was 13.1%. The protein content improved by 29.6%. The lysine content increased by 126%, reaching 11.3 g·kg. The threonine content increased from 6.10 to 10.3 g·kg. The phytate content was decreased to 3.97 g·kg. The in vitro digestibility of dry matter and protein increased to 62.8% and 76.1%, respectively.

Conclusions: These results indicated the feasibility of improving the feeding value of wet distiller grains and wheat bran by the symbiosis of T. reesei and C. utilis. © 2024 Society of Chemical Industry.