The Studies On Producing Surrogate Of Fish Meal By Mixed Strains Fermentation

In order to relief the shortage of fish meal, cut down the cost of feedstuff, solid statefermentation technology was used to degrade anti-nutrition factors, increase nutritioncomposition in soybean meal (SBM) and cottonseed meal (CSM). And then, producesurrogate of fish meal.A strain with high protease activity (30.71U, measured by folin-phenol) was screenedfrom soil, by casein plate screening technology. It was defined as Bacillus subtilis after initialidentification, named Bacillus subtilis Bs11. The free amino acids of SBM medium (soybeanmeal:wheat bran:corn flour=7:2:1, to call SBM for a short below) after solid-statefermentation by Bs11reached81.32mg/g. Compared the true protein and free amino acidscontent of SBM by Bs11, Saccharomyces cerevisiae Sc1, Saccharomyces cerevisia Sc2(single strain, two strains, three strains fermentation), three strains was the best. The best ratioof inoculation is Bs11∶Sc1∶Sc2=2∶1∶1. To optimize the process conditions forincreasing true protein and free amino acids in SBM fermented by the three strains mentionedabove, orthogonal experiment was designed including inoculum level, solid-liquid ratio,incubation temperature, incubation period. The optimum fermentation conditions arepresented as follows: inoculation5%(v/w), solid-liquid ratio1:1, fermentation temperature at30℃, fermentation period of72h. The content of the true protein and free amino acids inSBM reached41.88%and90.76mg/g, increased22.03%and88.18%respectively, comparedto unfermented SBM.The Czapek’s medium containing acetic gossypol instead of sucrose as carbon sourceand malt extract medium with acetic gossypol were used for plate screening. Through thesemethods, a strain named Aspergillus oryzae As3.811with high efficiency of free gossypoldetoxification in CSM was screened out from the strains preserved in the laboratory.Compared the free gossypol content of CSM fermented by As3.811, Saccharomycescerevisiae Sc1, Saccharomyces cerevisiae Sc2(single strain, two strains, three strainsfermentation), As3.811single strains was the best. To optimize the process conditions for detoxification of free gossypol in CSM medium (CSM:wheat bran:corn flour=7:2:1,to callCSM for a short below) by As3.811, orthogonal experiment was designed including inoculumlevel, solid-liquid ratio, incubation temperature, incubation period. The optimum fermentationconditions for free gossypol detoxification are inoculum level5%(v/w), solid-liquid ratio1:1,incubation temperature at35℃, incubation period of36h. Free gossypol of CSM reduced to117mg/kg compared to unfermented CSM.The rate of degradation researched78.13%.Main nutrition and anti-nutrition factors levels of SBM and CSM were determined afterfermentation. Nutrition levels increased significantly and anti-nutrition factors levelsdecreased obviously in SBM and CSM with no bad smell. SBM and CSM could substitutefish meal in certain extent as protein content of them got close to the level of the third degreefish meal(protein content of the third degree fish meal≥50%) and free gossypol contentreduced to safety range(free gossypol of CSM in feedstuff≤1200mg/kg).