Bioaugmentation of ensiled Caragana korshinskii Kom. with a rapid start-up Pediococcus acidilactici and cellulases: Fermentation profiles, bacterial community composition and enzymatic saccharification

The present study investigated the effects of Pediococcus acidilactici and an exogenous fibrolytic enzyme on fermentation profile, structural carbohydrates degradation, enzymatic saccharification, and dynamics of the bacterial community of Caragana korshinskii silage. Chopped C. korshinskii was either not treated (control) or treated with P. acidilactici (PA) at 100,000 colony-forming units/g fresh weight; Acremonium cellulase (AC) at 0.3 g/kg fresh weight; or a combination of P. acidilactici and Acremonium cellulase (PA+AC). Each treatment was prepared in quadruplicate and ensiled in mini-silo bags for 3, 7, 14, 30, and 60 d, respectively. After 60 d of ensiling, all additives increased lactic acid and acetic acid concentrations (P < 0.001) and decreased propionic acid, non-protein nitrogen (NPN), and ammonia nitrogen (NH3-N) concentrations (P < 0.001) compared with the control. Meanwhile, the highest lactic and acetic acids and lowest non-protein nitrogen (NPN) and ammonia nitrogen (NH3-N) (P < 0.001) were observed in PA+AC treated silage. In addition, the application of additives decreased the silage pH values during the early-to-mid stage (3 to 30 d) with the PA+AC group having the lowest value. Compared with the control, all treatments increased ferulic acid concentration and degradation of neutral detergent fiber (NDF) and acid detergent lignin (ADL) at 60 d, meanwhile, the highest values (P < 0.05) were obtained from PA+AC silage. PA treatment exhibited a lower performance in the degradation of structural carbohydrates but performed the best in glucose yield and cellulose conversion (P < 0.05). The bacterial community in all silages consisted mainly of P. acidilactici over the entire fermentation process, and the highest abundance of 6-phospho-beta-glucosidase was observed in PA treated-silage at the mid-later stage of ensiling. These results indicate that pretreating C. korshinskii improved its silage quality and potential use as a lignocellulosic feedstock for the production of bio-product and biofuel.