Enhancing feeding value of corn distiller's grains with solubles via fungal co-cultured solid-state fermentation for monogastric animal nutrition

Corn distiller's dried grains with solubles (cDDGS) as a major co-product from dry-grind corn-ethanol processes have imbalanced key amino acids (AA), high indigestible fiber and phytate, and risk of mycotoxin contamination, which limit its inclusion rate in monogastric animal diets. This study used cellulolytic fungus Trichoderma reesei (TR), two zygomycete fungi Mucor indicus (MI) and Rizopus oryzae (RO) and their co-cultures to ferment corn wet distiller's grains with solubles (WDGS) with the supply of soybean hulls and urea via solid-state fermentation at 28 °C for up to 9 days. Compared to control (non-inoculation) and monoculture, TR and RO co-culture (TR+RO) after 6 and 9 days showed more balanced branch-chain AA (BCAA) of valine (Val), leucine (Leu), and isoleucine (Ile), higher phytate reduction (56–61%), lower concentration of deoxynivalenol (DON), zearalenone (ZEN) and total aflatoxins (AFT). However, the treatments with MI (MI, RO+MI, TR+MI) showed increase of DON while reduction of ZEN compared to treatment without MI. Due to fast growth of RO and MI, the co-culture of TR+MI and TR+RO after 3 days of fermentation improved total AA by 32 % and 28 %, respectively, higher than monoculture of TR (18 % after 3 days). Compared with co-culture, monoculture of TR produced feed with higher in vitro dry matter digestibility (IVDMD) with 22–43 % improvement from control, and higher in vitro digestibility of total AA (IVDAA) with 35–50 % improvement from control, the similar level was also achieved by co-culture of TR+RO after 6 days of fermentation. Therefore, co-culture of TR+RO and monoculture of TR in fungal bioprocessing could provide a feasible solution to improve the overall feeding value of the cDDGS.