Studies On Potato Pulp Solid-state Fermentation For Production Of Active Proteins As Feed

China is a large potato production country in the world both in growing area and production. Consequently, the huge amount of potato residue, which is produced in the production process of potato starch, has low feeding value and can contribute to the environmental pollution. According to this, treating potato residue with the microorganism fermentation would be a desired method to improve the nutrition value of potato residue, and then improve the feeding value of potato residue to some extent.In this study, the active protein feed was generated from potato residue fermented with various strains in solid culture using wheat bran as auxiliary material. At fermentation stage, the selection and combination of strains, the concentrate ratio of fermentation culture, and the fermentation conditions have been taken into consideration and optimized. The main research progress were as follows:(1)In the single strain experiment, the crude protein content, proteinase activity and cellulase activity in the fermented product fermented with Aspergillus Niger HF3 and Aspergillus Niger Z9 were significantly improved, while the content of crude fiber presented dramatic decrease. Therefore, Aspergillus Niger HF3 and Aspergillus Niger Z9 can be utilized as the optimal strain of protein feed on potato residue.(2)In double strain fermented test, the combination of Aspergillus Niger Z9 and Saccharomyces cerevisiae PJ was the optimal strain combination considering the crude protein content, crude fiber content, proteinase activity, cellulase activity in the fermented product. When inoculated by Aspergillus Niger Z9 and Saccharomyces cerevisiae PJ at the ratio of 1:1 for 4 days, the crude protein content,crude fiber content, proteinase activity, and cellulase activity reached(41.72±0.58) %,(8.47±0.11) U/g,(1344.93±10.56) U/g and(120.87±0.46) g/kg, respectively.(3)In the experiments of optimizing fermentation culture, the optimal culture medium was determined, which was potato residue 80%, urea 5%, water ratio 1:1.5, bran content 15%. The primary and secondary order of three factors have influence on the crude protein content were urea content, water ratio, and bran content, while the primary and secondary sequence of these three factors have effect on proteinase activity and cellulase activity were water ratio, urea content, and bran content. When the potato residue was fermented under this condition, the crude protein content, proteinase activity, and cellulase activity reached(38.01±0.80) %,(1593.03±5.29) U/g, and(112.36±1.74) U/g, respectively.(4)The result from the key parameters optimistic experiment of solid fermentation showed that the optimal condition was packing height 2cm, fermentation time 5d, and fermentation temperature 27℃. The primary and secondary order of these three factors have influence on the crude protein content was fermentation temperature, packing height, and fermentation time, while the primary and secondary order of these three factors have influence on cellulase activity was packing height, fermentation time, and fermentation temperature. When the potato residue was fermented under the optimal condition, the crude protein content, proteinase activity, and cellulase activity reached(41.24±1.04) %,(1376.19±43.45) U/g, and(124.33±0.28) U/g, respectively. Additionally, the species of amino acid in the feed increased dramatically and the quality of feed improved as well.