Screening Of Forage Bacillus And Study On Its Application In Fermention Of Soybean Meal

One probiotic bacillus was isolated from the feces of healthy piglets and identified as Bacillus subtilis NCU901, which was applied to preparation of high-quality fermented soybean meal(SBM). The probiotic properties of Bacillus subtilis NCU901 were investigated in vitro. In addition, the fermentation conditions of the strain in solid-state fermentation were optimized.This paper used the piglets fresh feces as the test specimen. Four strains were isolated after initial screening of acid tolerance, bile salts resistance and bacteriostasis activeness. After determination by colony morphology, physiological and biochemical characteristics and molecular identification, 2 were identified as Bacillus licheniformis NCU903 and Bacillus pumilus NCU904.And the other 2 strains were identified as Bacillus subtilis, named as Bacillus subtilis NCU901 and Bacillus subtilis NCU902, espectively. The Bacillus subtilis NCU901 had the best bacteriostasis activity.The growth curve of B. subtilis NCU901 was measured. 0-2 h was lag phase of the bacterial growth, 2-20 h belonged to logarithmic phase, while 20-120 h was stationary phase. Afterwards, the thermal resistance of B. subtilis NCU901 was examined. It was found that the survival rates of B. subtilis NCU901 at different temperature increased for a short time and then decreased. The survival rates of B.subtilis NCU901 were 52.75%, 33.46% and 24.42% after incubation at 60°C, 80°C and 100°C for 20 min, respectively. Incubation at 40°C for 20 min almost made no change. Moreover, The study of B. subtilis NCU901 revealled its strong ability to inhibit pathogenic bacteria, respecially Enterobacter sakazakii CMCC45401 and Staphylococcus aureus 26003. Furthermore, the survival rate of B. subtilis NCU901 was 81.75% after 5-h incubation in PBS with pH 2.0. The survival rate of B.subtilis NCU901 was 73.29% after 5-h incubation in PBS supplemented with 0.5 g/100 mL bile salt. In addition, B. subtilis NCU901 exhibited high tolerance in artificial gastrointestinal fluid. After 12-hour manipulation, the viable bacteria remained 8.85Lg(CFU/mL).Research on B. subtilis NCU901 solid state fermentation of soybean meal. By the single factor experiment, orthogonal experiment and verification experiment, the optimized condition for fermentation was: culture for 36 h at 37°C with inoculum concentration of 6%, and the ratio of material to water was 1:0.8. In addition, the viable cell concentrations were 10.62 Lg(CFU/g), 10.45 Lg(CFU/g), 9.76 Lg(CFU/g)and 9.26 Lg(CFU/g) after drying in drying oven at 40°C, 50°C, 60°C and 70°C,respectively. And after vacuum drying at 60°C, the viable cell concentration reached10.12 Lg(CFU/g). Considering the cost and the energy consumption, the drying temperature was set at 40°C. Moreover, after storage for 6 months, the viable cell concentration remained 9.93 Lg(CFU/g).