| Asparagus has high edible and medicinal values and is widely planted in our country. After harvest season, there are nearly one million tons of the asparagus old stem which have not been used except for rotten naturally and burning directly. It causes a tremendous waste of resources. Some scholars have analyzed the nutritional components of asparagus old stem, and proved that it extremely rich in nutrients and contain18kinds of amino acids. So, asparagus old stem is an excellent high-quality feed resources to be worthy to be developed. The main aim of this paper is to convert asparagus old stem into feed for ruminant animals, which was produced by solid-state fermentation (SSF) experiments with mixed microorganisms. The main work of this research is screening the fermentation strains and culture medium, optimization of SSF culture medium, and optimization of SSF conditions.By SSF experiments with single strain and mixed strains, the microbial strains those could converted asparagus old stem into high-protein feed for ruminant animals were screened. The results showed that the strains combination of the ratio2:2:3of Penicillium sp.F-5, Aspergillus F-25and Chaetomium atrosporum F-21was proved to be the best combination. After SSF for five days by this strains combination, in the fermented products, the soluble protein and crude protein contents reached respectively4.80mg/g and11.18%g, which was39.94%and38.54%higher than that of control; the cellulose content reduced from22.74%to22.32%,which was1.85%lower than that of control; the lignin content reduced from12.90%to10.53%, which was18.37%lower than that of control. Therefore, it could be concluded that the asparagus old stem could be converted into good high-protein feed for ruminant animals by SSF.By single factor and orthogonal experiments, unsterilized asparagus old stem medium were optimized. The single factor experimental results showed that the65%was the optimal moisture content,4%of (NH4)2SO4was the best nitrogen source, bran was the most suitable auxiliary material, the ratio of81%:17%of the main material to the auxiliary,material was proved to be the best in single factor experiments. The orthogonal experimental results showed that the optimal culture medium were as follows:asparagus old stem of89%, bran of9%,(NH4)2SO4of2%, moisture content of62%, natural pH.By single factor and orthogonal experiments, the SSF conditions of asparagus old stem were optimized. The single factor experimental results showed that28℃was the optimal temperature,10%of inoculum was the optimal inoculum size, and five days was the optimal fermentation time. The orthogonal experimental results showed that the optimal SSF conditions were as follows:temperature of28℃, inoculum size of7%, fermentation time of four days.In summary, in order to produce ruminant animal feed by SSF experiments with mixed strains, the optimal culture medium were as follows: asparagus old stem of89%, bran of9%,(NH4)2SO4of2%, moisture content of62%, natural pH; the strains combination of the ratio2:2:3of Penicillium sp. F-5, Aspergillus F-25and Chaetomium atrosporum F-21was proved to be the best combination; the optimal SSF conditions were as follows: temperature of28℃, inoculum size of7%, fermentation time of four days. |
