Study On The Mixed Fermentation Of Tilapia Byproducts And Soybean Meal For New Protein Feeds

Tilapia byproducts are a premium animal protein source, while soybean meal isthe most widely used vegetable protein source. At present, Tilapia byproducts aremainly used to produce fish meal, but due to its poor technology and facility, thedigestibility of the product is very low. With the development of the global aquacultureindustry, the supply of fish meal is difficult to meet the needs of the industry, whichleads to the soaring price of fish meal, the increasing cost and the decreasing economicbenefit of the aquaculture, and the reducing enthusiasm of farmers, so now activelyseeking to the replaceable high-quality protein raw material of fish meal is the key toguaranteeing the sustainable development of the aquaculture.To alleviate above serious situation, this paper studied the effect of the probiotics,enzymes and trace elements on the fermentation of Tilapia scraps and soybean meal, tryingto produce new protein feeds being rich in small peptide. The new feed was a wonderfulcombination of animal and plant protein, which, meanwhile, undoubtedly provided newideas for future research, and it also was a high value application. As the most idealsubstitute, the new feed could efficiently resolve the severe shortage of fish meal, thuspromoting the healthy development of the aquaculture in China. The main findings areas follows:(1)Taking the degree of hydrolysis (DH) as the overall index, the optimalfermentation conditions were optimized through the single factor and the orthogonalexperiment. The optimum ratio of Tilapia wastes to soybean meal was1:1; the optimuminoculum size of bacillus subtilis, yeast, lactobacillus were0.6‰,0.06‰and0.0015‰，respectively. Under these conditions, the degree of hydrolysis reached27.27%; the degreeof degradation of tripsin inhibitor and phytic acid were up to65.2%and53.3%; the proteinin fermented liquid was well hydrolyzed by the analysis of SDS-PAGE electrophoresis andhigh performace size exclusion chromatography (SEC), particularly all the soybeanβ-conglycinin and mostly glycinin.the size of the obtained protein was mainly about5000Da, while4.9%of them was small peptide under1000Da.(2)The effect of the non-starch polysaccharide enzymes (including xylanase,cellulose, mannase and β-glucanase) on fermentation was studied, and results showed thatonly xylanase could obviously accelerate the hydrolysis. The optimum hydrolyzed conditions were investigated with response surface methodology (RSM), results were asfollows: neutral protease0.1%, temperature40℃, time53h. And the degree of hydrolysiswas31.94%; under1000Da was32.08%, the small peptide under1000Da was12.26%.The contents of Cu, Mn, Fe, Zn elements in the fermented products were determined byatomic absorption spectrometry, and the content of any trace element was up to thestandard of the fishmeal.(3)The effect of Cu, Mn, Fe, Zn on the fermentation was obtained through theBox-Behnken experimental design, and findings showed that the optimal dosage of Cu2+,Mn2+, Fe2+and Zn2+were40,450,900and400mg/kg, respectively; and DH was up to34.68%. The chelating rate was detected by the gel filtration chromatography to determinethe relationship between chelating rate and DH. The results showed that,Cu2+chelatingrate was increased in the beginning and then decreased,the chelating rate of Fe2+andZn2+was down with adding more.(4) The nutritional components and security of the feed were analyzed by sensoryevaluation, conventional and un-conventional physical and chemical test. Results wereshowed below: the feed had pure color and fragrant flavor; the contents of the nutritionalcomponents excluding the protein were in accord with the national standard of the firstlevel of fishmeal; the gastric protein digestibility, the degree of degradation of tripsininhibitor and phytic acid were95.26%,89.13%, and61.2%; The content of amino acid inhydrolysis products was42.11%, essential amino acids accounted for36.14%,non-essentialamino acids accounted for63.86%.The content of free amino acids was3.921,the essentialacids were1.698,accounted for43.3%,the non-essential acids were2.223,accounted for56.7%.The content of under1000Da was37.59%, small peptide under1000Da was risedsignificantly to13.19%.The total viable count and the heavy metal content were also wellconsistent with the national standard.