A Study Of Bacterial Protein Feed Produced By Sweet Potato Residue Fermentation

Sweet potato is the residue after the extraction of starch by processing enterprises,Because it wasn’t got reasonable use that cause the waste of resources and environment pollution.Through the production of bacterial protein feed for solid state fermentation of sweet potato residue,not only beneficial to environment protection,but also can reduce the pressure of the protein feed resources.Therefore,sweet potato residue fermentation is scientifically valuable and has a great prospect in the market at the same time.Three experiments were conducted to investigate the optimum single strain, fermentation route,strains combination and their proportion,best fermentation conditions and the apparent metabolic energy(AME),energy apparent metabolic rate(AMR),crude protein apparent metabolic rate of fermented products for solid state fermentation of sweet potato residue.The main works and results as follows:Experiment 1. Four strains of yeast,four strains of aspergillus niger(H),five strains of bacillus subtilis(K) and one strain of lactobacillus(R) were adopt in this study. Solid fermentation were conducted under the same fermentation condition and the content of crude protein of products was the measure indicator for single strain selection.According to the results,the strain numbered as candida utilis(C) in the four strains of yeast had the highest crude protein was 12.53% after fermentation;the strain numbered as 41126 in the four strains of H had the highest crude protein was 13.67% after fermentation;the strain numbered as Y111 in the five strains of K had the highest crude protein was 10.63% after fermentation.The selected four strains were used to choose the optimum route of fermentation,C+H(1:2,1.5:1.5,2:1) formed aerobic fermentation,C+R+K(1:1:1) formed anaerobic fermentation.two times of fermentation consist of first aerobic fermentation and dried its products for second anaerobic fermentation.The result showed that H:C=1:2 had the highest crude protein was 13.53% after aerobic fermentation:the content of crude protein in production of anaerobic fermentation was 8.88%;H:C=2:1+C:R:K=1:1:1 had the highest crude protein was 15.11% after two times of fermentation.Thus,two times of fermentation was the optimum fermentation route and H:C=2:1+C:R:K=1:1:1 was the best strains combination and proportion.Experiment 2. Three inorganic nitrogen sources which is NH4Cl,(NH4)SO4 and Urea were chose in this experiment,adding them into sweet potato residue by set up levels that 0.5%、0.75%、1%、1.25%、1.5% distinctions.the fermentation was carried out according to the best strains combination and two times of fermentation has been set.Crude protein of products was the measure indicator for optimum N sources and the amount of added.The result showed that adding 1% Urea had the highest crude protein was 11.78%.Then chose Urea as inorganic nitrogen sources of the culture medium.An orthogonal experiment of four factors at four levels L16(44) was conducted that the factors and levels were as following:fermentation time(1d,2d,3d,4d).fermentation temperature(28℃,30℃,32℃,34℃),the amount of N source(0.75%,1%,1.25%,1.5%) and the amount of strains(1%,2%,3%,4%).The optimum conditions as follow:time of fermentation,3d;temperature of fermentation,28℃;the amount of N source,1%;the amount of strains,3%.Under the above conditions,crude protein concentration in the fermented products was 12.35%,which was higher 85.99% than raw material with equal Urea added before fermented, energy and amino acids also improved different degree,especially several essential amino acids improved obviously.Experiment 3. According to the optimal condition that was screened in Experiment 2 was used in expanded fermentation,tested crude protein and energy in fermented products after paved and dried.Experimental designed five groups which is fermented products of sweet potato residue(A),raw material of sweet potato residue(B),B adds oil(C),Wheat powder with equal protein(D), Wheat powder adds oil with equal protein and energy(E).Force feeding adult Huangyu broiler 40g respectively,tested the AME、AMR and crude protein apparent metabolic rate in fermented products with the method of total fecal collection.According to the results of AME,group A was significantly higher than group B(P < 0.01),which was higher 33.46% than control group of sweet potato residue.with no significant difference between group C and E(P>0.05),group D was significantly higher than each other group(P< 0.01); According to the results of AMR,group A was significantly higher than group B(P< 0.01),which was higher 20.30% than control group of sweet potato residue,with no significant difference between group C and E(P>0.05),group D was significantly higher than each other group(P< 0.01); According to the results of crude protein apparent metabolic rate,group A was significantly higher than group B(P< 0.01),which was higher 85.24% than control group of sweet potato residue,37.07%higher than group C(P<0.05),with no significant difference between group E(P>0.05),group D was significantly higher than each other group(P<0.01).