Screening Bacillus For Degradation Of Soybean Meal Anti-nutritional Factors And Optimization Of Fermentation Conditions

Soybean meal (SBM) is an important source of dietary protein in the poultry and swine industry. The presence of anti-nutritional factors (ANF) contained in soybeans have been recognized as the key factors that affect thenutritional value of SBM and other soy products.This study was about isolation of Bacillus subtilis for degradation of soybean meal anti-nutritional factors from soil, and identification of the strains, fermentation optimization, in order to explore new resources for industrial production and optimization of fermentation.169 strains of Bacillus were isolated from different soil samples, for spore heat resistance characteristics, heating at 80℃for 10min. The anti-nutritional factors such as the soybean antigen proteins (11S,7S) and trypsin inhibitor proteins were the only nitrogen source medium, by this way to screen bacillus. After plate screening and fermentation rescreening, a strain named B9 was obtained for its great capability of degradation the soybean glycinin and P-conglycinin proteins, trypsin inhibitor (TI).B9 was bacillus subtilis by its physiological and biochemical experiment and analysis of its 16S rDNA sequence. By the comparing experimental with industry bacteria B3b, B9’s degradation of soybean glycinin andβ-conglycinin proteins were 63.12% and 52.56%, the degradation of trypsin inhibitor was 57.24%.Compared with the B3b respectively increased 39.28%,48.22% and 2.82%.Learning from the fermentation technology of our laboratory, this study selected neutral protease and the B9 complex Fermentation. The fermentation process was optimized by using the single factor analysis and the orthogonal design method. Determined the optimum fermentation parameters were:temperature 37℃, fermentation period 66h, anticipate water to compare 1:1(w/v), yeast extract 1%, inoculation quantity 2.5%, neutral protease concentration 100μ/g.Analysis of the nutritional value of soybean meal samples, raw soybean meal to make CK, compared the nutritional changes before and after optimization. The results were as follows:1. The improvement of nutrition indicators. Crude protein content of SBM was increased from 46.55% CK to 51.87% after optimization, and was near to 51.34% before optimization. Peptide nitrogen (TCA-NSI) content was increased from 1.82% CK, 13.29% before optimization to 20.68% after optimization. The total amino acid content was increased from 44.23% CK,45.08% before optimization to 47.75% after optimization, and was 5.92% higher than before optimization. The most of the amino acids have been increased after optimization, especially Ala, Ile, Met, Lys, His, the content of those was 10% higher than before optimization. The content of Soy isoflavones was increased from 0.893 (OD260nm) CK,1.654 (OD260nm) before optimization to 1.883 (OD260nm) after optimization, significantly increased its antibacterial activity.2. The improvement of small molecular peptides. The CK was mainly Macromolecules proteins, the protein components of molecular weight and above in 160000Da were accounted for about 71.45%, were the main molecular weight distribution. The content of macromolecular proteins before optimization is smaller than the CK. The protein components of molecular weight and above in 160000Da was reduced to 35.15%, the component of 3000Da-1000Da was about 42.65%, the small peptide fraction component of 1000Da and below was about 22.2%. The content of macromolecular proteins after optimization was the least. The protein components of molecular weight and above in 160000Da was only 20.49%, the component of 3000Da-1000Da was about 58.85%, the small peptide fraction component of 1000Da and below was about 22.75%.3. The decreasition of anti-nutritional factors. Optimized fermented soybean products of Fat oxidation activity was eliminated from-0.138 CK to none, SBA was also removed eliminated from 20480 units CK to none. Urease activity was reduced from 0.35U CK,0.236U before optimization to 0.11U after optimization. The content of TI was reduced from 1977 (TIU/g) CK,1149 (TIU/g) before optimization to 538 (TIU/g) after optimization.