Research On Production Of Protein Feed By Fermenting Potato Residue

With the prevalence of strategy of potato as staple food in China,the potato yield increased steadily year by year.It is estimated that in 2020,the annual output of potatoes will reach about 130 million tons.The rich potato resources continue promoting the development of potato processing industry,which improve the added value of potatoes and create a variety of ways to ensure that people increase production and income.Potato starch is one of the most important deep-processing products.Potato residue is a by-product produced in the process of potato starch production.The main components include polysaccharides such as starch,cellulose,pectin and a small amount of protein.The residue was directly abandoned,buried or dehydrated as animal feed,usually.However,abandoned and buried residue would pollute the environment,resulting in waste of resources,and for the feed its low nutritional value,poor palatability and bad feeding effect haven't been solved.Therefore,the potato residue has not been fully and effectively utilized.The beneficial microbial fermentation could make full use of the available components in the potato residue through a series of physiological and biochemical reactions in the microbial body,to increase the protein content of potato residue,and produce a certain bioactive factors.The potato residue can be turned waste into treasure in this way,which will solve the problems of difficult treatment,serious pollution and low utilization rate of potato residue from many aspects.In this paper,the potato residue was used as the research object to study the preparation of certain bioactive protein feed products by microbial fermentation of potato residue.The study was carried out from several aspects,such as sterilization of fermented raw material or not,mixed fermentation,liquid fermentation after enzymolysis,optimization of solid-state fermentation medium and process conditions.The specific content and results are as follows:(1)The effects of sterilization and non-sterilization of fermented raw material on the fermentation products were investigated by using the true protein content,cellulase activity and acid protease activity.The results showed that the single fermentation of Aspergillus niger was higher than that of the other,and the sterilization was better than the non-sterilization,but each index increase is limited,increased by 8.14%,4.28% and 21.60%,respectively.There was no significant difference between the two kinds of treatment.Combined with the actual production costs and industrialization and other issues,the selection of fermented raw materials do not be sterilized.(2)To explore the effects of the combination of multiple strains and their proportion on the protein feed,to discuss the symbiotic relationship between the different strains and to screen out the best strains compatibility and proportion of the protein produced by the potato residue fermentation.The results showed that the synergistic effect of two strains was better than that of three strains,and the compatibility of Aspergillus niger and Brewer's yeast with ratio of 1:1 was the optimal strain combination.The true protein content of fermentation product could reach about 17.87%,which was increased by 171.17% compared with that before fermentation.Acid protease activity and cellulose activity reached 1187.93 U/g and 61.77 U/g,respectively.(3)Preparation of protein feed by liquid fermentation through single factor test and orthogonal test,screening out the optimum amount of enzymes.The content of true protein in final fermentation products was assayed,and the liquid fermentation and solid-state fermentation were compared and analyzed.The results showed that the potato residue could be prepared certain protein content(14.69%)of the feed products by compound enzymatic hydrolysis,but compared with the solid-state fermentation,the protein content of the latter was higher(16.24%),which was 10.55% higher than that of the former.Combined with the market background of feed industry,the solid-state fermentation with small investment,simple operation and low energy consumption can better meet the needs of the development of feed industry.(4)The single factor and orthogonal tests were carried out on the nutrient components that affected the growth of fermentation strains.The optimum fermentation medium of potato residue was obtained: raw material-accessories ratio 85:15,liquid-solid ratio 1:2,urea concentration 2.00%,ammonium sulfate concentration 1.00%.Based on the optimized medium,the content of true protein,acid protease activity and cellulase activity in the fermentation product were 18.11%,1126.56 U/g and 83.68 U/g,respectively.The nutritional quality of the protein feed was greatly improved.(5)The single factor and response surface tests were conducted to study the effects of fermentation conditions on the quality of potato residue fermentation products.The optimum conditions for the fermentation of potato residue were as follows: fermentation temperature was 31?,fermentation time was 100 h,and the material layer thickness was 3 cm.Under these optimized conditions,the content of true protein,acid protease activity and cellulase activity in the fermentation product were 18.86%,1275.10 U/g and 89.33 U/g,respectively.There are many kinds of amino acids in fermentation products.The contents of total amino acids and essential amino acids increased by 254.75% and 296.23%,respectively,and the anti-nutritional factors such as crude fiber,starch and pectin decreased correspondingly.The above studies could be concluded as follows: the fermentation medium was not sterilized and directly fermented by Aspergillus niger and Brewer's yeast(Aspergillus niger and Brewer's yeast with ratio of 1:1).The fermentation medium components were: raw material-accessories ratio 85:15,liquid-solid ratio 1:2,raw material-accessories ratio 85:15,urea concentration 2.0%,ammonium sulfate concentration 1.0%,and the fermentation conditions were: fermentation temperature 31?,fermentation time 100 h,the thickness of the layer 3 cm,and total inoculum 10%,then the high-quality protein feed was obtained.The content of true protein,acid protease activity and cellulase activity were significantly increased by 303.84%,1999.97% and 251.69% respectively,compared with the raw potato residue.And the amino acids in the product were complete,with reasonable collocation.At the same time,the anti nutritional factors such as crude fiber,starch and pectin were largely degraded.The nutritional quality of protein feed was better,which is beneficial to digestion and absorption of animals.