Fungi can improve stover digestibility due to their ability to secrete oxidative enzymes that depolymerize lignin, allowing the rumen microorganisms to access the polysaccharides of the plant cell wall. Some ascomycetes have shown good delignification capability; however, they have been scarcely evaluated for their ability to improve corn stover (CS) ruminal digestibility. We evaluated the laccase induction by CS of the CMU-196 strain of the ascomycete fungus Didymosphaeria sp. (syn. = Paraconiothyrium sp.). Also, we analyzed the capacity of such strain to modify the cell wall of CS and to improve its digestion by the ruminal microbiota. The CMU-196 strain showed a maximum extracellular laccase activity of 39.74 ± 0.24 U/L when an aqueous stover extract (SE, 10% v/v) was added to the growth medium. The addition of ground stover (GS, 2% w/v) increased the activity to a maximum of 262.27 ± 0.58 U/L. In solid-state fermentation (SSF) assays of GS, the strain degrades cell walls, destabilizing the vessels and tracheids of plant biomass; the protein content reaches a maximum of 33.2 g/kg dry matter (DM) at 70 days, while the crude fiber content shows the highest level of 314 g/kg DM at 14 days. SSF treatment of the CS increased the in vitro ruminal production of gas in a fraction that was considered nondigestible at 18 h, and gas production increased by 14% with respect to the untreated GS at 14 days. The CMU-196 strain can digest the plant cell wall and improve ruminal CS digestibility at a level equivalent to several basidiomycete species.

Centro Multidisciplinario de Estudios en Biotecnología Facultad de Medicina Veterinaria y Zootecnia Universidad Michoacana de San Nicolás de Hidalgo Km 9 5 Carretera Morelia Zinapécuaro Col La Palma CP 58893 Tarímbaro Michoacán Mexico

División de Estudios de Posgrado Facultad de Ciencias Médicas y Biológicas Dr Ignacio Chávez Universidad Michoacana de San Nicolás de Hidalgo Ave Rafael Carrillo esq Dr Salvador González Herrejón Col Cuauhtémoc CP 58020 Morelia Michoacán Mexico

Instituto de Investigaciones Agropecuarias y Forestales Universidad Michoacana de San Nicolás de Hidalgo Km 9 5 Carretera Morelia Zinapécuaro Col La Palma CP 58893 Tarímbaro Michoacán Mexico

References provided by Crossref.org